INVESTIGATION OF THE LOSS OF CREOSOTE COMPONENTS
FROM RAILROAD TIES
Ayan Chakraborty
A thesis submitted in conformity with the requirernents for the degree of Master of Applied Science
Gnduate Department of Chernical Engineering and Applied Chemistry University of Toronto
Q Copyright by Ayan Chakraborty 200 1
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Investigation of the Loss of Creosote Components
from Railroad Ties
Master of Applied Science. 200 1
Ayan Chakraborty
Departrnent of Chemical Engineering and Applied Chemistry University of Toronto
The present study was conducted to measure the loss characteristics of some of the PAH
and phenolic components of creosote from creosote impregnated railroad ties. 56 cm long sections
of two new and two old ties were subjecied to simulated environmental conditions of UV radiation,
infrared radiation, water spray and freezing temperatures in Plexiglas chambers. Of the three
different loss mechanisms, namely, leaching, bleeding and vaporization, leaching was found to be
the major loss process (accounting for 50% to 96% of the losses For the four different ties). The
PAH components lost by leaching and bleeding were found to be directly related with the arnount
initially present in the ties. Unlike vaporization and bleeding, Ieaching was found to be an
important mechanism in both new and old ties. A fugacity-based mass balance mode1 on
phenanthrene and fluoranthene predicted that these PAH cornponents released from the ties were
below toxic levels.
ACKNOWLEDGEMENTS
The author would like to take this opportunity to express his sincere gratitude to:
ProJ P d Cooper and Pro5 Chartes Jia for their invaluable advice and support, and consistent
encouragement throughout this work, starting from the conceptual stages to the very end. The
helpful suggestions and support of al1 the members in the two research groups are also
appreciated.
Prof: D. N. Roy and Dr. Samir Konar for their sincere help regarding the Gas Chromatography
used for the work and also for their valuable advice on numerous complex situations.
Mr. Tory Ung for his immense help in converting the theoretical design aspects of the
experiments into reality.
Last, but not the least, my parents in India for their constant support and encouragement, not
withstanding the rift of distance.
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
CHAPTER ONE. INTRODUCTION
CHAPTER TWO. LITERATURE SURVEY
2.1 Creosote as a Wood Preservative
2.2 Composition of Creosote
2.3 Release to the Environment
2.4 Loss Mechanisms of Creosote
2.5 Toxicity of Creosote
2.6 Physicnl-Chernical Properties of Major PAH Compounds
2.7 Fugacity Mode1
2.8 Objective of Present Work
CHAPTER THREE. EXPEWMENTAL WORK
3.1 Characterization of the Ties Studied
3.1.1 Sampling for initial distribution of creosote in the ties
3.1.2 Extraction and separation of PAHs
3.2 Quantification of the Loss of Chemicai Constituents of Creosote 2 1
3.2.1 Weathering chambers 2 1
3.2.2 Weathering cycles and sampling procedure 2 1
3.2.3 Extraction and separation of P.4Hs and phenolics from solvents used in UV-IR treatment 25
3.2.3 Extraction of PAHs and phenolics from the paper towels 35
3.2.5 Extraction of PAHs and phenolics from the leaching chamber 28
3.3 Small-Scaie Laboratory Tests 28
3.3.1 Specimen preparation 29
3.3.2 Quantification of the amount evaporated 30
3.3.3 Quantification of the amount leached 3 1
3.4 Estimating the Variation of Different Compounds along the Length of the Tie 32
3.5 Analysis of PAHs and Phenolics with GC-FID 32
3.6 Quality Control 37
CHAPTER FOUR, RESULTS AND DISCUSSIONS
4.1 Distribution of Creosote in the Ties
4.2 Quantities of PAHs Lost through Various Mechanisms
4.2.1 PAH compounds from four different ties
4.2.2 Quantities of PAHs leached aRer 5 cycles
4.2.3 Progressive leaching of the PAHs
4.2.4 Relating the leaching characteristics
a) Correlation behveen amozin~s leached and solzibility 58
6) Correlatioi2 benveen percentage leaching and solribiliy 6 1
C ) Correlatio~ between amozints leached and initial content (retention) 62
4.2.5 Correlation of the amounts vaporized with di fferent parameters 64
a) Correlation between amounts vaporized and vapor pressure 64
b) Correlation between amounts vaporized and iuitial retention 66
cl Correlation benveen percentage ioss of initial contenrs of rhe conzpounds throrrgh vaporization and vapor pressure 67
42.6 Correlation between bleeding and retention 69
4.2.7 Possible causes for the lack of correlations of amounts vaporized and leached with vapor pressure and solubility respectively 7 1
4.3 Phenolic Compounds 73
4.4 Comparison between Results of Tie Sections and Small-Scale Laboratory Experiments
4.4.1 Comparison of vaporization and leaching patterns between the plug and the experimental tie section of the first new tie 77
4.4.2 Correlation of vaponzation with different parameten 80
4.4.3 Correlation of leaching with di fferent parameters 8 1
4.5 Comparison of Total Losses to the Initial Retention 83
4.6 Variation along the Length of the Tie and Comparison with Initial Content 86
4.7 Environmental Impact 88
4.7.1 PAH compounds - Preliminary Fugacity Modei Approach 88
(a) Assumptions made iri the model calcrrlations 89
(b) Mudei orrtpirts 9 1
(c) T u x i c i ~ effects 94
(d) Sensitivity analpses 96
4.7.2 Phenolic compounds
CHAPTER FIVE. CONCLUSIONS
CHAPTER SIX. FUTURE WORK
REFERENCES
APPENDICES
Appendir A. Cross Sectional Views of Different Tie Sections
Appendix B. Recommendations for Future Work
Appendix C. Mode1 Outputs
vii
LIST OF TABLES
Table
1. Selected physical-chernical properties of the PAH compounds studied
2. Different environmental cycles and the corresponding conditions
3. Number of samples (N) and relative standard deviations (RSD) for different injections of same sample as well as different samples of the same Ieachate
4. Retention ( k d m b f dry wood) based on analysis of the extract and percentage of different compounds in different ties at the beginning of experîments
5 . Retention (kg/m3 of weared wood) based on analysis of the extract and percentage of di fferent compounds in di fferent ties at the beginning of esperiments
6. Comparison of total percentage losses and weighted percentage iosses from different ties after al1 the cycles conducted for each of the four ties
7. Comparison of total percentage losses and weighted percentage losses from different ties afterfive cycles conducted for each of the four ties
8. Variation in retention (expressed as kg/m3 of dry wood) of creosoie components dong the length of the first new tie after being exposed to the environmental cycles in Plexiglas chambers
9. Specifications of the six-compartment evaluative environment
10. Fugacity Model: Predicted distribution and concentrations (g/rn3) in different environrnental compartments
LIST OF FIGURES
Figures
1. Set up used for exposure to UV and IR radiations in Plexiglas chamber
2. Set up for leaching in Plexiglas chamber
3. Set up for measuring amount vaporized from small-scale laboratory tests
4. Set up for measuring leached quantities in small-scale labontory test
5. Temperature prognmming for the PAH compounds
6. Sample chromatogram for standard PAH compounds
7. Temperature programming for the phenolic cornpounds
S. Sample chromatogram for standard phenolic compounds
9. Sarnple chromatograph obtained for leaching of PAHs
10. Sample chromatograph obtained for leaching of phenolics
1 1. Penetration of creosote into different ties: L" New Tie: top left; 2" New Tic: bottom left; lSt Old Tie: top right; 2" Old Tie: bottom right
12. Comparative rates of loss from lSt New Tie (average of 8 cycles)
13. Comparative rates of loss from 2%ew Tie (average of 6 cycles)
14. Comparative rates of loss from 1" Old Tie (average of 7 cycles)
15. Comparative rates of loss from znd Old Tie (average of 5 cycles)
16. Leachate flux from each tie (average of 5 cycles)
17. Cumulative percentage Ieaching from each tie atter 5 cycles
18. Relative amounts of different compounds leached aRer 5 cycles for each tie (amounts added cumulatively after each cycle)
19. Cumulative leaching loss pattern of naphthalene, acenaphthylene, fluorene and anthracene from the four ties
Page
23
24
30
3 1
33
34
34
35
36
37
20. Cumulative leaching loss pattern of acenaphthene, phenanthrene, fluoranthene and pyrene frorn the four ties
2 1. Cumulative leaching loss per unit area of four PAH compounds after each cycle for each of the four ties
22. Cumulative leaching loss per unit area of the other four PAH compounds after each cycle for each of the four ties
23. Average rate of leaching (pg/cm'.cycle) for 1" New Tie
74. Average rate of leaching (~g/cm2.cycle) for 1" Old Tie
25 . Average rate of leaching (pg/cm2.cycle) for 2" New Tic
26. Average rate of leaching (pg/cm2.cycle) for 2nd Old Tie
27. Relationship between amount leached (pg) and initiai content (pg dry wood) after 8 cycles for I" New Tie
28. Relationship between amount leached (pg) and initial content (pg dry wood) after 7 cycles for 1" Old Tie
29. Relationship between amount leached (pg) and initial content (pg dry wood) atter 6 cycles for z " ~ New Tie
30. Relationship between amount leached (pg) and initial content (pg dry wood) after 5 cycles for 2" OId Tie
3 1. Average rate of vaponzation (pg/cm'.cycle) for the 1'' New Tie
32. Average rate of vaporization (pg/cm2.cycle) for the 1 " OId Tie
33. Average rate of vaporization (pg/cm2.cycle) for the znd New Tie
34. Average rate of vaporization (pg/cm2.cycle) for the 2nd Old Tie
35. Amounts (pg) ofchemicaIs vaporized vs. initial content (pg) for the 1" New Tie
36. Amounts (pg) of chemicals vaporized vs. initial content (pg) for the 2" New Tie
37. Amounts (pg) of chemicals vaporized vs. initial content (pg) for the 1" Old Tie
38. Amounts of chernicals bled (pg/crn') vs. initial content (pg) of these chemicals in the 1" Xew Tie
39. Amounts of chernicals bled (pg/cm2) vs. initial content (pg) of these chernicals in the znd New Tie
40. Cornparison of losses of phenolic components by different mechanisms from the four ties
4 1. Cornparison of losses of phenolic components (expressed as percentage of initial content) by different mechanisms from three ties 74
42. Cornparison of the relative importance of the different loss processes frorn the four ties after five cycles for each
43. Cornparison of the relative importance of the different loss processes (Iosses expressed as percentage of initial content) from the four ties after five cycles for each 76
44. Cornparison between vaporization rates (pg/crn2. hr) from the plug and from the 1" New Tie
45. Cornparison bctwcen lcaching rates (yg/cm2. hr) from the plug and from the 1" New Tie
46. Amount vaporizcd (pJcm2. hr) vs. vapor pressure (Pa) for plue S 1
47. Amount leached (pg./crn'. hr) From the plug vs. initial content (pg) 52
CHAPTER ONE. INTRODUCTION
Wood presewation is the pressure or thermal impregnation of pesticidal chemicals
into wood to a depth that would provide effective long-term resistance to attack by fungi,
insects and marine borers. By extending the service life of available timbers. wood
preservation reduces the harvest of already stressed forestry resources, reduces operating
costs in industries such as utilities and railroads, and ensures safe working conditions
where timbers are used as support structures.
Of the different wood preservatives, creosote is the only one used in Canada for
treating railroad ties. Creosote is a variable mixture of srveral organic compounds
obtained by the pyrolysis of bituminous coal. There are several pathways by which
creosote may finally end up in the environment. Creosote is lost in service from the ties
by three mechanisms: vaporization, bleeding and leaching. Since certain fractions have
relatively high vapour pressure, these should be expected to evaporate relatively rapidly.
Some of components are hirlÿ water soluble, and hence, should tend to leach
substûntially to the surroundings. At the same time, some of the creosote components
may physically bleed out of' the ties in service, particularly under high temperature
exposure.
The present project aims at quantiQing the relative amounts lost by these three
processes under laboratory conditions that simulate field exposure. Sections of two new
ties and two old ties were subjected to vanous environmenial conditions, i.e., exposure to
ultraviolet and infrared radiations, water spray and beezing temperatures. This study
under simulated environmental conditions was supplemented by small-scale experiments
under more controlled conditions.
Creosote is a variable mixture of different classes of organic compounds, the most
predominant one being the polycyclic aromatic hydrocarbons (PAHs). Between 20 to
40% of the total weight of creosote can be attnbuted to sixteen PAHs that are defined as
priot-ity polIutants by the United States Environmental Protection Agency (EPA). Some
of the creosote components are also potential carcinogens, the most important of these
being benzo[a]pyrene. Therefore. the amount and rate of loss of creosote from railroad
ties in service might be high enough to pose a serious threat to the surrounding
environment and biota. At the same time, the rate of loss of the compounds from the ties
though di fferent mec hanisms would also providc an indication of the e ffectiveness of
creosote as a wood preservative.
In view of the above facts, a thorough knowledge of the rate of loss of creosote
from ties in service, and also the nature of loss processes and the effect of these losses on
the environment and biota becomes extremely vital and relevant.
CHAPTER TWO. LITERATURE SURVEY
2.1 Creosote as a Wood Preservative
The chemicals predominantly used in Canada for wood preservation are i )
creosote. i i ) pentachlorophenol and iii) ûqueous formulations of arsenic and copper with
chromium or ammonia (e.g., chromated copper arsenate and ammoniacal copper
arsenate). Of these, creosote has long been used as a preservativc for industrial products
such as railway ties, marine and land piling, posts, poles and wood block flooring.
Creosote has been pressure impregnated into wood products since Bethcll patented the
full cell vacuum-pressure treating process for creosote treatment of wood in the U.K. in
1839 (Betts. 1990). By the late 1950s, it was estimated that about 2000 million creosote-
impregnated sleepers were in use throughout the world (Betts, 1990).
2.2 Composition of Creosote
Chemically, creosote is a complex and variable mixture produced From the
destructive distillation or pyrolysis of coal. According to the American Wood Preservers'
Association (AWPA) (1977), creosote is defined as the distillate produced by high
temperature carbonization of bituminous coal at a continuous boiling range of
approximately 275 O C , begiming at about 175 O C . Creosote does not occur naturally in
the environment; it is created by high-temperature treatment of coal (coal tar creosote), or
sometimes of beech or other wood (wood creosote) or fiom the resin of creosote bush
(creosote bush resin). The general chemical composition of creosote has long been known
3
because of work on coal tar (Rhodes, 1945). Creosote typically contains more than 300
cornpounds, which are classified by Environment CanaddHealth Canada ( 1993) into the
following five major classes of compounds:
Aromatic hydrocarbons including polycyclic aromatic hydrocarbons (PAHs),
benzene, toluene and xylene (PAHs can constitute up to 90% of creosote)
Phenolics including phenols, cresols, xylenols and naphthols ( 1 to 3 % of creosote)
Nitrogen-containing heterocyclics including pyridines, quinolines, acridines,
indolines, carbazoles ( 1 to 3 % of creosote)
Sulphur-containing heterocyclics including benzothiophenols ( 1 to 3 % of creosote)
Oxygen-containing heterocyclics including dibenzofurans (5 to 7.5 % of creosote)
(U.S. EPA, 1987).
However. some other studies revealed somewhat different compositions of
creosote, and the phenolic constituents have been reported to be as high as 10%.
2.3 Release to the Environment
Most railway ties are treated with a 50150 mix of creosote and petroleum oil to a
target retention of 56 kg/m3 creosote. In Canada, creosote has been used for treating
railway ties since 19 1 1 (Environment Canada/Health Canada, 1993). Railway ties make
up the most of the volume of wood treated with creosote (approximately 80% of the
approximately 20,000 tonnes of creosote used annually in Canada). Railway ties also
constitute the largest number of creosote impregnated waste products generated in
Canada. The major railways decommission 4.5 X 106 ties per year (450,000 m3 of wood)
containing an estimated 20.2 X 106 kg of creosote (Environment CanadaMealth Canada,
1993). It is estimated that 90% of al1 railway ties removed each year are reused. This
leaves roughly 2.02 x 106 kg/year of creosote in discarded railway ties as creosote waste
products. The Bte of these discarded ties is largely unknown, though some of them are
landfilled.
In the past, most of the ties removed from service were bumed on the side of the
track, although some of higher quality were reused as right-of-way fence posts. as ties on
secondary lines or for landscaping tirnbers. However. with curent controls on open
buming and incineration of creosote treated wood. the disposal of used tics has becomc a
concem. Apan from being used for landscaping, present day uses of used ties range from
retaining walls that have minimal exposure to humans, to borders of raised bed vegetable
gardens that may contact humans as well as food.
Releases from creosote wood preservation facilities are probably confined to
historical events resulting from poor operating practices. These rcleases were relatively
small compared to releases from other sources. The available evidence, which is limited
and not very conclusive, indicates that the quantities of PAHs entering the environment
Born treated wood in service are also small (Ingram et al., 1982).
The environmental impacts of creosote from marine use in North America have
been comprehensibly studied by several researchers, but studies on railway ties are
largely lacking. The loss of creosote frorn treated wood placed in the marine environment
has been variously described as high as 70% to as low as "not detectable". Much of this
variation can be explained by the variation in the sample size used by the researchers.
Invariably, studies employing small samples (e.g., thin panels or srnaIl blocks of treated
wood) report relatively large losses of creosote, particularly during the first year of
exposure (Sweeney et al., 1956; Baechler et al., 1970a; Colley, 1972; Miller, 1972b;
Webb, 1980).
The most comprehensive study about loss of creosote from railroad ties is
contained in a study conducted in Switzerland by Kohler et al. (2000). The study found
that approximately 9 million wooden railroad ties are installed in the country, each being
treated with approximately 15 kg of creosote. During the average service life of 20-30
years, about 5 kg of creosote is emitted, corresponding to an emission factor of 210
mg/(m2.day). equivalent to 0.2 kg/(tie.year). PAH emissions for an average railroad tie
were found to be about 0.5 kg (considering 16 PAH cornpounds studied in this
experiment). conesponding to an emission factor of 2 1 rng(m2.day). The study also
concluded that about 1710 t of creosote components are being emitted from railroad tics
from the Swiss railway nehvork every year.
Wan (1991) analyzed ballast from railway rights of way and the adjacent ditch
water and sediment for PAHs. The occurrence and concentration of sixteen selccted
PAHs were detennined. Al1 sixteen PAHs were observed in both the ballast and the ditch
sediments. In the ballast. the total PAH concentration ranged from 1.56 to 58.77 g/m3
while in the ditch sedirnenis, it was 1.89 to 1 168.7 pg per gram of sediment. The author
also mentioned that apart frcm the railway ties, locomotive engines could be a major
source for the PAHs. Other possible sources could include herbicides used for the control
of weeds, oil and grease from the axles, and track lubrication. On the whole, the study
conciuded that the replacement of the creosote treated ties would eliminate the major
source of PAHs.
2.4 Loss Mechanisms of Creosote
As mentioned above, creosote is Iost from the railway ties by three processes:
volatilization, bleeding and leaching. The AWPA Manual of Recommended Practice
contains a glossary of terms in which "bleeding" is defined as "the exudation and
accumulation of liquid preservative on the surface of the treated wood". A revision of the
elossary alters the definition to read "the exudation of liquid preservative from treated I
wood. The exudates rnay evaporate, remain liquid or harden into a semi-solid state". At
any time after pressure impregnation with crcosote, timbers may exude creosote
components, either slightly or appreciably, locally or generally, ternporarily or
continuously. Usually, the amount that bleeds passes through a maximum, although it
may subsequcntly fluctuate. Bleeding is undoubtedly stimulated by sunlight, probably
due to the timber becoming heated by absorption of solar radiation. It is generally
accepted that timber which has been floated or ponded (water stored) or seasoned slowly
from a high initial moisture content is more permeable to creosote and therefore, less
likely to bleed than timber which is not.
Stasse and Rodgers (1965) found that losses of O to 230°C fraction from small
surfaces treated with creosote ranged from 78 to 90 percent (depending on the type of
creosote). whereas losses of the other fractions were al1 below 52 percent and were
mostly in the range between 20 and 40 percent. Colley (1972) confirmed that almost 100
percent of creosote fractions boiling below 230°C were leached from thin panels in 6.5
years. Losses of highcr fractions ranged from 57 to 75 percent. Bernuth (1987) cited
Dutch studies descnbing loss of creosote when 1 m' of treated wood was leached in 140 1
of water, renewed daily. A rapid loss of naphthalene and fluoranthene was noticed.
Naphthalene decreased from a concentration of 1.2 g/m' to not detectable after 8.5 days,
while fluoranthene was reduced from 35 mg/m2 to almost zero after 35 days. Guruprasad
et al. (1995), in a study of PAH compounds in creosote impregnated waste materials from
across Western Canada, concluded that out-of-service railroad ties can contain very high
concentrations of PAHs even after several decades of use.
According to the findings of' Ingram et al. ( 1982) about the migration of creosote
components from treated marine piling sections, the major PAH components which
migrated from creosote-treated wood into water were naphthalene, phenanthrene,
acenaphthene, dibenzofuran, fluoranthene and 2-methyl naphthalene. However, a much
higher perccntage of the lower molecular weight PAHs, such as naphthalene and
acenaphthene, were tound in the water. For example, 2-methylnaphthalene (MW = 132)
made up 5.86% of the PAH in the wood samplcs analyzed, but represented 9.52-9.67
percent of the PAHs that migrated into water. In contrast, fluoranthene (MW = 202) made
up 10.44 percent of the PAHs in the wood, but only 1.57- 1.6 1 percent of the PAHs
migrating into water. This pattern is expected owing to the lower solubility of the higher
molecular weight PAHs in water.
Temperature also had a substantial effect on the rate of migration of the PAHs
from treated wood. At 20-40°C, the major PAH components migrating from unaged
wood into fresh water were naphthalene, acenaphthene, phenanthrene, dibenzofuran,
fluorene and 2-methyl naphthalene. The total concentration of the 15 major PAHs studied
in water was 1287-1735 ppb at 20°C, 1984-2864 ppb at 30°C and 2599-3479 ppb at 40°C
(Ingram et al., 1982).
A laboratory system was developed by Xiao et al. (2000) for assessing the
migration of creosote-treated Douglas-tir wood immersed in still or flowing fresh water,
and the wash-off effects by rainfall. The study was a background for developing
"predictive models for assessing the risk of creosote use in aquatic environments". For
the experiments, lumber treated with creosote was subjected to leaching in a plastic water
tank maintained at 35 O C . Samples were taken at different time intervals to compare the
leaching rates. Eight PAH components were studied with the help of Gas
Chromatography with Flame Ionkation Detector using solid phase micro-extraction
(SPME) technique. The study found that leaching for acenaphthene, dibenzofuran.
fluoranthene, phenanthrene and fluoranthene followed a linear relationship for the first
eight hours and that the concentrations of al1 creosote components tested were lower than
their reponed water solubilities.
2.5 Toricity of Creosote
Creosote serves to maintain a chernical bamer against termites and against decay
for long penods of time, as shown through more than 40 yean of continuous field testing
conducted by the U.S. Department of Agriculture Forest Service (Western Wood
Preservers Institute, 2000). Several manufacturers guarantee their treated wood to resist
decay and insect attack for 40 years or longer. However, the fact that creosote is effective
against a broad spectrum of organisms (wood destroying fungi, insects and marine
borers) indicates that its presence may influence the activity of soi1 or water microflora
(Henningsson, 1983).
Some chernicals in creosote, such as tar acids and the naphthalenes. are
biodegradable and soon get decomposed and assimilated by microflora. Other fractions
like fluorene, chrysene, anthracene and pyrene are much less biodegradable.
Although creosote as such is considered to have relatively low toxicity, some of
the components in it are listed as potential carcinogens (Xiao et al., 2000). Of the total
weight of creosote, between 20 and 40% can be attributed to sixteen PAH compounds
defined as priority pollutants by the United States Environmental Protection Agency
(EPA), the most toxic one being benzo[a]pyrene (Kohler et al., 2000). The acute and
chronic toxicity of creosote was investigated and no increased cancer risk was detected
for those workers handling and using creosote on a daily basis (Alscher and Lohnert,
1985). The toxicity of creosote to birds and fish has been reported by Webb (1975). The
"No Observed Effect Levels" (NOEL) were 2 15 pprn for the Bobwhite quail. 2 150 ppm
for Mallard duck and 0.32 ppm for rainbow trout. The corresponding LCjo were 1261,
10388 pprn and 0.56-0.75 pprn respectively. For oral dose on rats, LDso is 3.8 g/kg (Betts,
1990).
A comprehensive review of the hazards of PAHs to fkh and invertebrates has
been compiled by Eisier (1987). According to this study, the PAHs that enter into the
aquatic environment are the most significant in ternis of potential harm to the living
beings as they become easily available for uptake.
As for the effects on humans, skin imtation is known to occur by exposure to
creosote vapour in the presence of sunlight. With regard to chronic effects, there is
insufficient evidence of an increased risk of skin cancer from creosote (Betts, 1990).
However, judging the overall impact of preservatives released from treated wood,
Webb and Gjovik ( 1988) cited a report by von Rurnker et al. ( 1975) of the Environmental
Protection Agency which concluded that available evidence indicated the environmental
hazard posed by creosote treated products is minimal. The same view is shared by some
other researchers as well. For example, Eisler (1987) concluded that the PAHs released to
the environment from wood preservatives are negligible compared to those released from
natural sources iike forest fires, and anthropogenic sources like coke production, catalytic
cracking in the petroleum industry, the manufacture of asphalt, heating and power
generation, controlled refuse incineration, and emissions from interna1 combustion
engines used in transportation. Webb (1980) concluded that creosote and its solutions do
not bio-accumulate despite the long record of use of over 100 years. According to this
study, available data show that components of creosote are biodegraded. Loss of creosote
and its solutions from treated wood were considered insignificant. Thus, this study
concluded that creosote treated wood products do not contaminate or harm the
environment, do not enter the food chain for eventual wildlife and hurnan consumption,
and can therefore continue to be used without significant harm to the environment.
As already stated, phenolic compounds constitute the second major class of the
creosote compounds. Phenolics in water are known to cause bad taste in fish for human
consumption at concentrations of 1 - 10 mg/l. (Henningsson, 1983). Effects on drinking
water that is chlorinated are evident even 3t concentration around 0.001 mg phenol per
litre. In order to avoid unacceptable effects on fish and drinking water. the suggested
phenol concentrations are below 0.1 and 0.000 1 mg/l respectively.
2.6 Physical-Chemical Properties of Major PAH Compounds
In order to correlate the different loss mechanisms to various parameters, a
knowledge of the physical-chemical properties of the different chemicals is essential. As
discussed later in the section on "Ekperimental Work", this study is mainly focussed on
eight PAH compounds, namely: naphthalene, acenaphthylene, acenaphthene, fluorene,
phenanthrene, anthracene, fluoranthene and pyrene. These chemicals have different
aromatic ring nurnbers (ranging from 2 to 4 rings) and widely varying structures, which
are naturally reflected in the physical-chemical properties. The structures of the different
compounds are shown below:
Naphthalene
Fluorene
Acenaphthylene
P henanthrene
Acenaphthene
Fluoranthene P yrene
Selected physical-chernical propertics of these chernicals are listed in Table 1 .
Table 1. Selected physical-chemical properties of the PAH compounds studied
Compounds 1 Mol Wt ( Melting Pt (OC) ( Vapor Pressure (Pa) 1 Solubility (mgIl)
I Mackay and Shiu, 1981
Naphthalene
Acenaphthylene
Accnaphthene
Fluorene
P henanthrene
Anthracene
Fluoranthene
P yrene
'' http://i~~t~\,v.chemt?ndcr.comi rcsult.asp 3. Verschueren, 1983
Sommerfield et al., 1983 (as cited in Mackay et al., 1993) Mabey, 1982 (as cited in Mackay et al.. 1993) ICF, 1985 .Miller et al., 1985
" Veith et al.. 1978 Windholz, 1976
'O CCREM, 1987 ' ' Kenaga and Goring, 1980
Twelve different phenolic compounds were also studied in the experiment.
However, since no attempt was made to correlate the results according to their physical-
128.19~
152.20'
80.6'
94'
10.9'
154.2' 9 5?
166.2' 1 116'
3 1.7'
0.207'
1 .d 0.0907'
0.026"
1 78 .X6
178.22~
0.893' 1 3.93'
3.9'
1.94'
1.2'
0.045'
202.3' 1 1 10.8' 1 6 . 6 7 ~ lo4"
202.26' 1 156' 1 8 . 8 6 ~ 1 0 ~ ~ '
99.5?
2 17.5'
0.26'
O. 148'
chernical properties, these properties were not considered relevant for discussion in this
section.
2.7 Fugacity Mode1
In order to evaluate the distribution of different wood chernicals in the
environment arnong different media, fugacity modeling can be applied. Fugacity is a
useful concept in environmental fate modeling since comparing the fugacities of different
environmental compartments shows whether or not the system is at equilibrium and the
direction of diffusive chemical transfer between the compartments (Mackay, 1979:
Mackay and Paterson, 198 1, 1982; Clark et al., 1988, Mackay 199 1 ). The use of fugacity
instead of concentration pemits a direct cornparison of chernical behavior among
compartments. Depending on the system in consideration, these compartments can be air,
water, soil, sediment, biota and suspended sediment. Each cornpartment is assumed to
occupy a particular volume according to the model. The Fugacity mode1 enables one to
predict in which compartment the compound, once released, tends to end up. Therefore, it
shows the tme potential of the harm that the compound poses to the environment.
Since creosote is a mixture of various compounds, the fugacity mode1 may only
be applied to individual components. Mychem Wood Protection Consultants Ltd. And
SENES Consultants Ltd. ( 19%) conducted a steady-state non-equilibnum chemical fate
model on twelve constituents of creosote. In the model, the entire chemical was supposed
to be released into the water compartment. The evaluative environment as developed by
Mackay (199 1) and supposed to represent a microcosm of the entire world was used in
the above study For defining the six compartrnents. The mode1 predicted that higher
percentage of the lower molecular weight PAHs were found in water compared to their
percentages in treated wood. Al1 the chemicals were found to be predominant in either
the water or the sediment compartment, with very Iiitle of the chernical found in air, soil,
suspended matter or biota. The relative quantities in water and sediment differed with the
solubility and molecular weight of the chemicals, with the more water soluble and lower
molecular weight compounds being predominant in the water compartment.
2.8 Objective of Present Work
Although several studies have been conducted to monitor the loss of creosote
components from different ireated surfaces, such studies directed specifically to railway
ties are Iimited. There have been studies directed to measure the concentration of
different PAH components of creosote in the surrounding ballast and ditchwater. In
addition, results from some research studies on the leaching characteristics of different
creosote components are also available. A few studies have also been conducted on the
loss of individual creosote components from railroad ties. Nevertheless, no concrete steps
have been taken to quantitatively attribute the amounts lost to the three different loss
processes, namely, volatilization, bleeding and leaching.
Therefore, the main objective of this study is to find out the relative importance
among these three different loss mechanisms from creosote-treated railway ties. Attempts
were made to correlate these loss mechanisms with different parameters such as vapor
pressure, solubility and initial retention of the individual conditions in the respective ties,
to help identi& the main factors governing these losses. At the same
based mass balance mode1 approach was followed to predict the
tirne, a fbgacity-
tendency of the
chemicals to end up in different environmental compartments as well as the potential
harm caused by these chernicals to the surrounding biota.
CHAPTER THREE. EXPERIMENTAL WORK
3.1 Charactcrization of the Ties
3.1.1 SarnpIe preparation:
Four creosote treated railroad ties were procured from the storage yard of the
Toronto Transit Commission at Downsview, Toronto. Of these, two were uninstalled ties
treated in 1995, and the other two were decornmissioned from the rail line after about 26
years in service. To begin with. the amounts of the different creosote components initially
present in the wood were quantified. The following methodology was adopted for this
purpose:
56 cm (22-inch) long sections were cut from each tie sufficiently far from the
ends for experimental exposure testing. With a chah saw, 0.5" thick slice of cross-section
was cut off from the unused section just adjacent to the 56 cm long experimental sections.
Each such slice was then ground to fine chips. These chips were then thoroughly mixed
to obtain a uniform mixture.
3.1.2 Extraction and separation of PAHs:
2 to 3 g portions of such ground wood chips from each tie were taken, allowed to
stand for about three hours to attain equilibrium moisnire content at the ambient
conditions, and then accurately weighed (accurate up to 0.01 g) on small pieces of
previously weighed paper towels (Kimwipes). Each such paper towel was subsequently
wrapped around the sample and secured with strings in the form of a "tea bag". After
weighing once again, the tea bag was placed in a soxhlet extractor, and the creosote
17
components were extracted using rnethylene chloride solvent. The extraction was
continued until the methylene chloride in contact with the tea bag appeared colourless,
which was attained after about six hours of extraction.
The extnct was collected and concentrated to 50 ml. The next step was to
scparate the phenolic compounds from the PAHs to ensure better detection by gas
chromatography. For this purpose, the methodology adopted by Cooper et al. ( 1991) was
followed: The concentrate was poured into a separatory funnel and 20 ml of 5% NaOH
solution (by weight) was added to it so that the pH rose above 12.5 to transfer the acidic
phenolic compounds to the aqueous phase. The contents of the sepantory funnel were
shaken for five minutes and altowed to stand for another fifteen minutes. The bottom
solvent layer. containing only the PAH compounds, was drained and stored in a 50 ml
conical flask.
20 ml dichloromethane was added to the remaining aqueous layer containing the
phenolic compounds. This was followed by the addition of 30 ml of 10% acetic acid
solution in order to tum the aqueous layer acidic enough (pH < 3.5) to tnnsfer the
phenolic compounds to the organic phase. The flask was shaken once again for five
minutes followed by fifteen minutes of standing to attain equilibrium. At the end of the
fifteen-minute period, the organic layer, now containing the phenolic compounds, was
tapped out from the separatory hnnel into another 50 ml conical flask and the aqueous
layer was discarded.
The PAH fraction was concentrated to 5 ml and the phenolic fraction was
concentrated to 2 ml (due to lower concentration than the PAH compounds) by
evaporation of the dichloromethane solvent by blowing air over it. 1 pl of each of ihese
samples was then injected in a Gas Chromatograph (GC) with FIame Ionization Detector
(FID) having the conditions as descnbed in Section 3.4.
From the arnounts of the individual PM components present in the above
concentrate, the respective amounts per unit weight of the wood can be calculated. In
order to detemine these weights per unit weight of dry wood, the following procedure
was adopted:
After each soxhlet extraction, the tea bag was allowed to attain equilibrium under
ambient conditions, and then weighed again. From the difference between the weights of
the tea bag before and after the extraction, the loss of chemicals from the tea bag dunng
extraction was calculated. Subsequently, the bag was oven dried to 104 "C and then
weighed again to find the weight of dry wood in the initial sample. The weights of the
different creosote components obtained as above from GC analysis were subsequently
expressed as a fraction of this dry weight of the wood. Thus,
where C = the particular creosote component initially present per unit weight of
dry wood ( p g k ) ,
rn, = amount (pg) of the particular compound detected by GC analysis,
m, = W. (g) of wood chips after extraction and oven drying at 104 "C
Multiplying the quantity in equation (1) by the density of the wood and making
the appropriate unit conversions, the retention of each compound in the corresponding tie
was calculated in the units of kg/m3.
Another way to express the initial content of the chernicals in the ties would be to
express the chemical retentions in the treated zone of the wood. For this purpose, the
cross sections of the different tie sections were studied, where the treated portion was
clearly visible. This treated area of the wood over the cross section was traced and plotted
on a graph paper. From this plot, the treated area was obtained as a fraction of total area.
Dividing the initial weight of the creosote components per unit weight of dry wood as
obtained above by the above fraction, one can obtain a measure of the initial weight of
the compounds per unit weight of the treated portion of the wood. Thus,
where C, = the particular creosote component initially present per unit weight of
treated wood (pg/g)
m, = amount (pg) of the particular compound detected by GC analysis,
m, = wt. (g) of wood chips after extraction and oven drying at 104°C
A, = treated area of the wood at a given cross section (as described above), cm'
A = cross sectional area of each tie = 9" X 7" = 63 sq. in. = 406.5 cm2
Multiplying the amount in equation (2) by the density of wood. the chemical
contents per unit volume of treated wood can be quantified.
3.2 Quantification of the Loss of Chemical Constituents of Creosote
3.2.1 Weathering chambers:
When out in the open, the ties are exposed to ultraviolet radiation. heat (i.e.,
infrared radiation), rain and freezing temperatures. These result in vaporization of the
chemical constituents of creosote, as well as in leaching and bleeding from the wood
surface. Therefore, in order to simulate each of these processes in a closed environment,
rectangular Plexiglas chamben having the dimensions of 60 cm X 48 cm X 48 cm were
constructed. The edges were sealed with silicone. Lids were constructed that sat snugly
on each of these chambers. On the inside of three lids were mounted an ultraviolet lamp,
a set of two infrared bulbs and a water sprinkler. The infrared bulbs had a power of 75 W
each, dissipating a total power of 150 W when in operation.
Fifty-six cm long sections were cut from each tie sufficiently far frorn the ends,
eliminating the possible extra leaching effects from the holes caused by the spikes near
the ends of each tie. Each 56 cm tie section was end coated with two layers each of coal
tar epony and water sealant silicone to prevent any leaching from the end grain.
3.2.2 Weathering cycles and sampling procedure:
Each tie was subjected to the following set of cycles:
i) The tie was first placed with the UV bulb lid on. The tie was subjected to UV
radiation constantly for a penod of 24 hours. Tubing was fitted on one side of the
chamber to allow the vaponzed compounds to escape. This tube was connected to
a vacuum pump drawing air at a rate of 40 rnlhin. The air flowing out was
passed through a series of three traps to capture different groups of compounds.
The first trap consisted of water to dissolve the water-soluble phenol compounds.
The second and third traps each consisted of dichloromethane (methylene
chloride) solvent to capture the PAH compounds and some of the higher
molecular weight and less water-soluble phenolic compounds. A layer of water
was kept on the top of the solvent layers to retard vaporization of the volatile
solvent. The method of including a water trap to capture the phenolics followed
by traps consisting of organic solvents was similar to the laboratory method
developed by Barry et al. (2000) used for evaluating the volatile organic
compound (VOC) emissions from the hot-press d u h g the manufacture of
particleboard. The total amount of water in the three traps amounted to 300 ml.
100 ml and 80 ml of dichloromethane were placed in the second and third traps
respectively. The pump was programmed to operate for 30 minutes followed by
three-and-a-half hours of rest. This four-hour cycle was continued six times over
each twenty-four hour period. The temperature inside the UV chamber was found
to be stable around 27 O C and no bleeding was observed at this temperature.
ii) Immediately after the UV cycle, the lid with the UV bulbs was replaced with the
lid with the IR bulbs. The temperature inside the chamber was maintained
constant at 54 OC using a thermostat, which disconnected the circuit as soon as the
temperature inside the chamber rose above 51 OC. The circuit was closed and the
IR lights were on once again as soon as the temperature dropped below 54 O C .
Unlike in the UV chamber, bleeding >vas noticed for some of the ties at this
temperature. in order to capture the bled components, the ties were wrapped witb
paper towels before each IR cycle was started. These paper towels effectively
absorbed whatever compounds bled out of the ties. For collecting the vaporized
components, the same set of traps as for the W cycle was used to trap the
chemicals evolving from the tie sections in the IR chamber. Moreover, Iike the
UV cycle, the pump used to pull out the vaporized components was operated for
thirty minutes followed by three-and-a half hours of rest, and the cycles were
repeated over a twenty-four hour period. Therefore. in each complete cycle, the
tie was exposed to intermittent UV and IR exposures for twenty-four hours each.
The set up used for the UV-IR cycles is shown in Figure 1.
iii) Following these operations, each tie was withdrawn from the chamber and placed
for two days in a Freezer maintained at a temperature of -5 "C.
UViCR bulb / Vacuum pump
LVriter
Solvent trap
Plexiglas shambet "+
Experimental tie section (56 cm X 23 cm X 18 cm)
- r 1
,' w
Water t n p
Figure 1. Set up used for exposure to UV and IR radiations in Plexiglas chamber
iv) Subsequently, the tie was taken out of' the freezer and placed in the leaching
chamber. The water in the sprinkler on the lid was forced through a pump
programmed to operate for one hour of operation followed by three hous of rest,
and each such four-hour cycle was continued for a total penod of forty-eight
hours. Six litres of water were used to fil1 up the pump and to partly fil1 up the
chamber. The pump had to be filled with water (pnmed) before the beginning of
any forty-eight hour run. In order to get a more concentrated sample for easier
detection dunng analysis, and also to reduce the othenvise immense volume of
water needed, the water was recycled by sucking the leachate in the charnber back
to the pump. The set up of the leaching chamber is as shown in Figure 2.
V ) Aftertheleachingcyc~e,thetiewastakenoutandplacedinthefreezeronceagain
for a period of forty-eight hours. after which it was again subjected to UV
radiation and the entire sequence was repeated.
Plexiglas chamber
Experimental tie section Water
Figure 2. Set up for leaching in Plexiglas chamber
The above cycles and the different conditions are summarized in Table 2. Such a
sequence was followed for each of the four ties. Once the first tie section was taken out of
the IR chamber and placed in the freezq a second tie section was put in the same
chamber and exposed to UV raciiation. The above sequence enabled the entire set of ties
to undergo one of the above cycles continuously without any tie having to sit around,
waiting for the completion of the preceding process.
Table 2. Different environmental cycles and the corresponding conditions
Treatment
UV radiation
IR radiation
Freezing
Leaching
Freezing
27
54
- 5
Room temp
-5
Exposure Time (hr) Sarnple collected Temp ( O C )
Vaporized components
Vaporized and bled components
None
Leached components
None
A total of eight such entire cycles were performed with one new tic, seven with
one oid tie, six with the other neiv tie and five for the other old tie. The unequal number
of cycles for the four different ties was due to a major breakdown in the Gas
Chromatography after the above number of cycles.
3.2.3 Extraction and separation of PAHs and phenolics from solvents used in UV-IR
treatment:
As noted above, the first trap to capture compounds coming out of the UV and IR
chamben contained only water to capture the phenolics. However, the two subsequent
traps consisted of both dichloromethane solvent and water. Despite covering the solvent
in these later traps with a layer of water, vaporization of the solvent could not be fully
prevented owing to the high velocity of air through it at the time of operation of the
purnp. Al1 the water and dichloromethane from the three traps were poured into a
separatory fumel. This enabled the solvent layer to be separated From the aqueous layer,
and thus, to quantify the exact amount of solvent remaining in the traps after the UV-IR
cycle. The final amount of dichloromethane in the second and third traps in al\ such
cycles typically amounted to slightly more than 50 ml. This solvent volume was
concentrated to exactly 50 ml by blowing air over it.
As noted above, the phenolics should be mostly captured in the water, although
some higher molecular weight and less water-soluble phenolic compounds might escape
the water to be absorbed in the dichloromethane. Therefore, in order to bnng al1 the
phenolic compounds in the aqueous layer, the following procedure was adopted. The
process was sirnilar to the one adopted by Cooper et al. (1994). which was used to
determine the leaching characteristics of creosote treated railroad tics.
The trapping solvents from the three traps combined, consisting of 50 ml
dichlorornethane and 300 ml water, were placed in a separatory funnel. 6 ml of 10%
acetic acid (by voiume) was added to the contents of the funnel so that the pH of the
water fell below 3.5. This facilitated the phenolic compounds, which are acidic in nature,
to be transferred to the organic layer. Subsequently, the flask was shaken thoroughly and
constantly for 5 minutes, following which, the contents of the flask were allowed to stand
(in order to let them attain equilibriurn) for 15 minutes. It was assumed that the phenolic
compounds were transferred as efficiently as possible from the aqueous to the organic
phase as a result of the above action. Therefore, at the end of the 15 minutes, the solvent,
which forms the bottorn layer, was tapped out from the funnel and the aqueous layer was
discarded.
The next step, once again, was to scparate the PAH compounds from the
phenolics in order to facilitate easier detection by gas chromatography. For this purpose,
the 50 ml solvent obtained in the last step was poured back into a smaller separatory
funnel and 20 ml of 5% NaOH (by weight) was added to it. The remaining extraction
steps were identical to those used for characterizing the ties, as descnbed in Section 3.1.2.
However, here, both the PAH and phenolic fractions were concentrated to 1 ml each.
Each of the two samples (i.e., PAHs and phenolics) was subsequently analyzed in
a GC/F 1 D as discussed earlier.
3.2.4 Extraction of PAHs and phenolics from the paper towels:
As rnentioned earlier, the compounds bleeding out of the tics were absorbed by
the paper towels wrapped around them during the exposure to IR radiation. After each
twenty-four-hour exposure to IR, the paper towels were unwrapped from the tie and those
portions of the towels where dark-coloured creosote was absorbed were cut off into small
bits. Al1 these pieces of paper towels were ultirnately wrapped into a small bundle in the
form of a teabag, and were secured with a piece of string. This bundle was then placed in
a soxhlet extractor and the creosote cornponents in the paper towels were extracted with
200 ml of dichloromethane for five hours.
At the end of the five-hour soxhlet extraction, the amount of dichlorornethane in
the round-bottom flask below the soxhlet that contained al1 the extractives was taken out
and concentrated to 50 ml by blowing air over it. The next process involved was once
again to separate the phenolic cornpounds fiom the PAHs to ensure better detection by
the GC. However, since al1 the compounds, including the phenolics, were supposedly
extracted in the dichloromethane, and there was no aqueous phase involved to begin with,
there was no need for the addition of any acetic acid in the first step. In other words,
analyzing the bled compounds was similar io the procedure for characterizing the ties, as
discussed above. Therefore, in this case, the fint step was the addition of 20 ml of 5%
NaOH to the above 50 ml of dichloromethane. This once again ensured that the pH was
high enough (N2.5) to drive the acidic phenolic compounds to the aqueous phase. The
subsequent processes leading to the separation of the PAHs from the phenolics was
exactly the same as in the case of the UV-IR traps, except that the PAH fraction was
finally concentrated to 2 ml instead of 1 ml.
3.2.5 Extraction of PAHs and p henolics from the leaching chamber:
As mentioned above, the leachate consisted of the creosote components that
leachcd into six litres of recycled water sprayed inside the leachate chamber. At the end
of each such forty-eight hour leaching cycle, 250 ml of the leachate was collected and
used for analysis. Dunng extraction, this 250 ml was transferred into a separatory funnel.
and 50 ml of dichlorornethane and 5 ml of 10% acetic acid (by volume) were added to it
to prornote solution of the creosote components in the dichloromethane. The rest of the
process was exactly the same as with the UV-IR traps.
Each of the collected dichloromethane samples was concentrated to 1 ml or 2 ml
depending on the concentration of the chernicals in the samples thernselves. If the
solution appeared too dark, it was apparent that it had higher concentrations, and such
solutions were concentrated to 2 ml instead of I ml. 1 pl of each of thesc samples was
then injected in the GCIFID.
3.3 Small-Scale Laboratory Tests
The expenments in the Plexiglas chambers were subjected to several
uncertainties. For example, despite efforts to seal the edges of the charnbers with silicone
as effectively as possible, a complete seal could not be obtained. This did allow some air
to get into the chambers dunng the W - I R cycles, but leR some doubt about the
efficiency of collection of the vaporized compounds, because some of the these
compounds might have escaped through these leaks. Moreover, some of the vaporized
compounds were seen to be absorbed at the sides of the Plexiglas chambers. At the same
time, due to the unavailability of more efficient pumps, the air could be sucked out only
for a half-an-hour period over each four-hour cycle. Due to ail these limitations, the
vaponzed compounds actually captured and analyzed might have been an under-
estimation of the actual vaporized arnounts.
To crosscheck the validity of the experiments in the chambers, and to verify the
observations from the different expenments with the tie sections, a small-scale laboratory
test was perforrnrd to evaluate evaporation and leaching under controlled conditions. The
basic set up was as discussed in the following section.
3.3.1 Specimen preparation:
A four-cm long cylindrical piug of 1.5 cm diameter was drilled out of the first
new tie. The plue was driiled from a location of the unused section adjacent to where the
56 cm tic section was cut, and from as close to the surface as possible, parallel to the
grain. This would give the plug similar treatment as the surface of the tie section used in
the chamben. Therefore, the creosote composition in the plug should closely
approximate the composition in the 56 cm section used in the experiments. The piug ends
were coated with coal tar epoxy.
3.3.2 Quantification of the amount evaporated:
This plug was placed in an Erlenmeyer flask having an outlet at its side. From the
top of the flask, a tube was drawn inside the flask, through which air was blown inside
the conical flask containing the plug. The side outlet was connected to tubing, which led
the outlet air into a trap containing methylene chloride solvent with a layer of water at the
top. Dunng the entire process, the conical flask was placed above a heatcr and the
temperature was maintained at 60 "C with the help of a thermostat. Air was blown
continuously for four hours, and the vaporized compounds were collected in the trap. The
set up is as shown in Figure 3. This set up was devoid of leaks and lacked the other
inefficiencies of the set up of the chambers. Moreover, the compounds sticking to the
sides of the glass walls were washed with the solvent at the end of' the four-hour run and
analyzed for any creosote components that vaponzed but condensed back on the walls
before reaching the traps. Subsequently, the methylene chloride solvent and water were
treated following the standard procedure as above.
Air ln Temperature sensor
To power S U P P ~ Y
4 Thermostat Water
DCM
Figure 3. Set up for measuring amount vaporized from smail-scale laboratory tests
3.3.3 Quantification of the amount leached:
Following the evaporation, the sarne specirnen was subjected to a controlled
water-leaching test. One end of the plug was attached to a steel rod connected to a
rotating shaft. When this shaft was made to rotate, the steel rod. dong with the plug at its
end, rotated with the shaft. The end-coated plug was then entirely imrnersed into 150 ml
of distilled water in a 300 ml beaker. This beaker. in turn. was immersed in a Cole-
Palmer ultrasonic water bath in order to maintain control
set up for this leaching test is shown in Figure 4. With
led temperature conditions. The
the water bath maintained at a
constant temperature of 25 O C , the shaft and the attached specimen were rotated for 8
hours at a fixed speed of 2 revolutions per second (120 rpm). At the end of the eight-hour
run. the 250 ml of water was collected and analyzed for PAH and phenolics content in the
same rnanner as with the leachate frorn the Plexiglas chambers.
Therefore, the vaporized and leached amounts were quantified in a controlled
environmeni, similar to the larger scale experiments in the c hambers, and the results from
the two sets of experiments were compared.
Ultra-sonic bath
Distilled 4 water
Figure 4. Set up for measuring leached quantities in small-scale laboratory test
3.4 Estimating the Variation of Different Compounds along the Length of the Tie
The initial retentions of the different compounds were calculated based on the
assurnption that the retention of the different compounds was the sarne throughout the
entire length of the tie. To venfy this assumption, and also to compare the change in
retention at the end of the experiments, the following experiment was performed with the
more heavily treated new tie (referred to in Chapter 4 as the first new tic):
At the end of the experiments in the chambers, three cross sections, each 0.5"
thick, were cut from the 56 cm (22") section of the tic. Two of these cross-sections were
taken from near the two extrcme ends of the tic section (the very extreme ends were
discarded because they were end coated). whereas the third was taken from the middle.
Analysis of each of these sections was perfomed in the same manner as for each of the
ties as described above in Section 3.1. The results from the three cross-sections were
compared with each other as well as with the composition of the same tie before it was
subjected to the environmental cycles.
3.5 Analysis of PAHs and Phenolics with GC-FID
1 pl of each of the above extracted samples was injected in a Gas
Chromatography (Shimadm Mode1 9A) with a Flame Ionization Detector having the
following conditions (Cooper et al., 1994):
A 30 m long DB-5 column was used, having an inner diameter of 0.32cm and
film thickness of 0.32 Pm. The pressure of the carrier gas (He), hydrogen and air were
0.5 kg/m2, 0.6 k& and 0.5 kg/m2 respectively.
32
For the PAHs, the following temperature program was adopted (Figure 5):
The initial column temperature used was 60 O C with a holding time of O min, and the final
temperature was 325 O C , with a ramp rate of 10 "Cimin. The final holding time was 3.5
min. The injector temperature as well as the detector temperature was 325 'C
3 2s'
Temp (OC')
60
Time (min)
Figure 5. Temperiture programming for the PAH compounds
A typical chromatogram for the standard PAHs is shown in Fig. 6.
For the phenolics, the temperature program adopted was as follows (Fig. 7):
The initial column temperature used was 40 "C with a holding time of 1 min. The
temperature was then increased to 140 O C with a ramp rate: 25 OC. With a O min holding
time at the temperature of 140 O C , the temperature was subsequently increased to 250 O C
with a ramp rate of 10 "Chin, where it was held for 3.5 min.
1. Solvent 2. Naphthalene 3. Xcenaphthylene
:. 4. Acenaphthene 5. Fluorene
, 6. Phcnanthrenc
9. Pyrene
Figure 6. Sample chromatogrrrn for standard PAH compounds
Temp ( O C )
I JO
40
Time (min)
Figure 7. Temperature programming for the PAH compounds
Fig. 8 shows a typical chromatogram for the standard phenolic compounds.
1. Solvent 2. Phenol 3. 2-chlorophenol 4. 3-methyl phenol 5. 2.4-dichforophenol 6. 2.6-dichlorop henol 7. 4-chloro-3-mcthy lphenol S. Trichlorophenols 9. Tetmchlorophenol 1 O. 4-nitrophcnol 1 1. Pentachlorophenol
Figure 8. Sarnple chromatograrn for standard phenolic compounds
The above temperature programs were used because they allowed the gradual
elution and proper detection of the compounds of interest very well. Before the samples
were injected, the GC/FID was calibrated with the above tempenture profiles separately
with PAH and phenolic cornpounds. The PAH standard consisted of the following
compounds in methanol : methylene chloride ( 1: 1 ) solvent: naphthalene, acenaphthylene,
acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene,
benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene.
benzo(a)pyrene, indeno( 1,2,3-cd)pyrene, dibenzo(a,h)anthracene, benzo(g, h,i)pery lene.
The phenolic standard consisted of the following compounds in 2-propanol solvent:
phenol, 2-chlorophenol, 3-methyl p henol (or m-cresol), 2,4-dichlorophenol, Z , 4
dinitrophenol, 4-chloro-3-methylp henol, 2,3,Ctric hlorophenol, 2,3,6-trichlorophenol,
2,4.6-trichlorop henol, 2,3,4,6-tetrac hlorophenol, Cnitrophenol and pentachlorop henol.
However, many of the higher PAH compounds gave very close and sometimes
overlapping peaks, whereas for some compounds like benzo(a)pyrene, the peak appeared
as a tiny spike from a gradually rising baseline at higher ternperatures. In this study, the
quantification of the PAHs was restrictcd to the first eight eluted compounds (namrly,
naphthalene, acenaphthylene. acenaphthene, phenanthrene, anthracene, fluoranthene and
pyrene) for which the peaks were clearly discernable and the data could be collected with
sufficient confidence.
Sample chromatographs for PAHs and phenolics are shown in Figs. 9 and 10
respectivel y.
1. Solvent 2. Naphthalene 4. Acenaphthene 5. Fluorenc 6. Phenanthrcnc 7. Anthracenc 8. Fluoranthene 9. Pyrenc
Figure 9. Sample chromatograph obtained for leaching of PAHs
1 . Solvent 10.4-nitropheno t 1 I . Pentachlorophenol
Figure 10. Sample chromatograph obtained for leaching of phenolics
3.6 Quality Control
The sixth leaching cycle for the second new tic was selected for rneasuring the
repeatabiiity of the sampling procedure for analyzing the leachate. as well as the
repcatability among di fferent injections of the same sarnple.
For this purpose, three different 250 ml portions were collected frorn the leachate
( h m within the experimental chamber) of the second new tie and each was extracted and
concentrated in the standard procedure as already discussed. L pl portions of each of
these samples were injected. The results of these three injections were compared with
each other for the different compounds. At the same time, three 1 pl injections were made
from the fint of these samples in order to get a cornparison between different injections
of the same sample. For the different samples of the same leachate, the relative standard
deviation (defined as SD/mean X 100, where SD represents the standard deviation) of the
different compounds was about 15%. For the different injections of the same sample, the
37
relative standard deviation for al1 the compounds ranged from 4 to 14%. It was only for
one compound (acenaphthylene) that the value was as high as 32%. This could be due to
the low quantity of acenaphthylene in the sample.
The relative standard deviations for the individual injections of the same sample,
as well as For 1 pl injections of the different samples of the same leachate as described
above are tabulated for each of the creosote compounds in Table 3.
Despite best attempts to seal the walls of the chambers with silicone. a complete
seal could not be attained. Moreover, the compounds partially stuck on the inner walls of
the Plexiglas chamben before reaching the traps, as observed from the stains on the
walls.
Table 3. Number of samples (8) and relative standard deviations (RSD) for
different injections of same sample as rvell as different samples of the same leachate
Compound ( Di f i rent injections of same sample I
Different samples of same leachate 1 I
Naphthalene
N = 3; RSD = 15%
Acenap hthylene
N = 3 ; R S D = 9 %
N = 3; RSD = 12%
N = 3; RSD = 14%
N = 4; RSD = 32% l I
N=3; RSD=9%
N = 3 ; R S D = 8 % 1
Fluorene I
Fluoranthene
P yrene
N = 3 ; RSD= 14%
N = 3 ; R S D = 5 % N = 3 ; R S D = 5 %
N = 3 ; R S D = 7 % N=3;RSD=6%
CHAPTER FOUR. RESULTS AND DISCUSSIONS
As stated in the section on "Experimental Work", one of the new ties was
subjected to eight cornplete environmental cycles whereas the other new tie was
subjected to six such cycles. These are noted as the fint new tie and the second new tie
respectively throughout the following discussions. The same applies for the two old ties,
the one subjected to seven cycles is designated as the first old tie and the one subjected to
five such cycles has been referred to as the second old tie.
4.1 Distribution of Creosote in the Ties
Of the four ties procured, three were made of maple and one (the second old tie)
was made of red oak. When sections of these ties were cut off in ordcr to get the 22" (56
cm) experimental sections, the depths of penetration of creosoie in cach of the ties
became visible. From a visual cornparison, it was evident that the preservative penetnted
much deeper in the fint new tie, as compared to the second new tie. as shown in Figure
1 1. The fact that the total retention was also quantitatively greater for the first new tie as
compared to the second new tie was verîfied by extracting the wood chips from the
respective ties, as elaborated in the section on "Erperimental Work". The second old tie
(the one made of oak), on the other hand, showed discontinuous bands of creosote in the
earlywood pores of each annual ring throughout the entire depth of the wood, and
extraction of the chips showed that retention was higher for this tie as cornpared to the
first old tie. The retention of the different creosote components is tabulated in Table 4.
Figure 11 . Penetration of creosote into different ties: 1" New Tie: top left; znd
New Tie: bottom left; 1'' Old Tie: top right; fnd Old Tie: bottom right
(The apparently different visual appearances of the cross sectional areas are
because of differences in elevation of the end surfaces)
As seen from Table 4, the two new ties have very different proportions of
different compounds. There was a much higher proportion of phenanthrene in the first
new tie compared to the second new tie, and at the same time, the amounts of fluorene,
phenanthrene, and total amount of phenolics in the first new tie largely surpassed those in
the second. The amounts of naphthalene and acenaphthylene were below detection limits
in the second new tie. But, on the other hand, acenaphthylene, fluoranthene and pyrene
were present at higher Ievels in the second new tie as compared to the first. Such
variability was also noted in the case of the two old ties. Although naphthalene,
acenaphthylene, acenaphthene and phenolic contents were below the detection limit for
M the second old tie, the amounts of the other compounds of interest in it were significantly
higher than those in the first old tie. Al1 these indicate the inherent variability in the
formulation of creosote. Such observation is consistent with the information available in
literature, which clearly mentions creosote to be a highly variable mixture of different
cornpounds.
Table 4. Retention (kg/m3 of dry wood) based on analysis of the extract and
percentage of different compounds in different ties at the beginning of experiments
1" New Tie
Naphthalene
Acenaphthylene
/ Anthracene 1 2.60 1 12.13 1 1.19 1 9.51 1 0.03 / 6.82 / 0.21 I
znd New Tie
1
Acenaphthene
Fluorene
1 Phenanthrene 1
Another point to note is that the target retention for creosote in the ties dunng
pressure impregnation is -56 kg/m3, as mentioned in the section on '*Literarure S~rve~v ",
kg/m3
0.04
0.01
1.03
11.69
73.79
0.22
, 2.50
15.80
Fluoranthene
Pyrene
Total phenolics
Total retention by analysis Estimated initial
preservative retention by extraction
lSt Old Tie I l
%
0.17
0.07
2"dld Tie 1 kg/m3
n.d
n.d. 1
0.40 1 3.21
0.03
0.02
0.26
21.41
191.64
%
n.d.
n.d.
0.02
0.12
0.09
1.21
100
kg/m3
0.03
0.01
0.13
1.63
4.55
0.94
5.83
2.07
1.88
0.17
12.48
36.0 1
n.d.
%
6.82
7.49 0.02 1 4.55
16.63
15.10
1.36
100
kg/m3
n.d.
2.27 1 n.d. I
22.73 46.72
0.02
0.16
0.06
0.44
4.00
0.10
4.55
36.36
13.64
100
0.65
0.30
n.d.
3.02
40.02
although the actual retention varies drastically. If the target retention is assumed to hold
good for both of the new ties, the compounds analyzed for the first new tie accounted for
roughly 33% of al1 the creosote cornponents present in the tie, whereas the corresponding
figure for the second new tie was roughly 20%. However, since there is no way of
knowing the actual retention afier treatment for each individual tie, the percentage
contents of the compounds analyzed could be widely different from above.
In Table 4, the row on "Estimated initial preservative retention" was calculated on
the basis of the difference in weight of the teabags before and after extraction in the
solvent extractor (as described in Section 3.1 2). This irnplies that the PAH and phenolic
components considered in this study constitute approximately 11% of the total creosote
and petroleum oil solvent contained in each of the first new tie and the first old tie. The
corresponding values for the second new tie and the second old tie were 34.6% and 7.5%
respectively. This may be compared with the study conducted by Kohler et al. (2000),
who found that the sixteen PAH compounds included in their work (which included the
eight PAH compounds considered in these expenments) constitute about 20 to JO% of
the total weight of typical creosote. Since the study conducted here considers only eight
of these sixteen compounds, the percentage of the cornpounds of interest in the total
creosote content can be considered to be in the expected range For al1 the ties. Although
the percentages might seem to be somewhat low for the two old ties and the first new tie.
it should be borne in mind that commercially available creosote is a mix of creosote and
petroleum oil. Therefore, the mass extracted From the tea bags was a mixture of creosote
and petroleum oil as well. The extracted mass might also contain some extractives
present in the wood itself.
The low proportions of the compounds of interest in three of the four ties can also
be explained in pan by comparing the percentage contents of the different creosote
components in typical AWPA PI-65 creosote (Betts, 1990). In this standard creosote
mixture, 23% of the compounds were left unclassified as "others", which can account a
lot for the probable variation in composition among the different ties.
Another estimate of al1 the different PAH and phenolic contents was obtained
based on the consideration of al1 the areas obtained in the chromatograph. These values
were based on the assumption that the sensitivities of the detector in the GC were similar
for al1 the compounds. This assumption was not precise, as the relative standard deviation
in peak areas for different P A H components per unit concentration was 57% (the
corresponding value for the phenolic compounds was 42%). However. it provides some
overall idea about the total content of creosote in the ties. According to this estimate, the
corresponding total retention values for the first new, second new, first old and second
old ties came out to be 124.0 kg/m3, 16.0 kg/m3, 2.2 kg/m3 and 4.0 kg/m3 respectively. As
expected, these values are less than the corresponding values listed in the row on
"Estimated initial preservative retention" in Table 4. The large variations for the second
new tie and the second old tie could be due to the quantities of rnost of the other
compounds being below the detection limit of the GCIFID.
Naphthalene concentration in AWPA Pl-65 creosote is as high as 12.9% (Betts,
1990). The percentages of naphthalene observed here are far lower than that, even for the
new ties. Acenaphthene concentration (5.8% of creosote) is also stated to be substantially
higher than the values observed here. This is reasonable for compounds having relatively
high vapor pressure, which can be lost from the new ties even while in storage (i.e.,
before they were procured for the expenments).
Table 5. Retention (kg/m3 of treated wood) based on analysis of the extract and
percentage of different compounds in different ties at the beginning of experiments
1'' New Tie
Naphthalene
2" New Tie
Acenaphthylene
Acenaphthene
Another way to compare the relative retention of the different ties is to estimate
the retentions per unit weight of treated wood. For this purpose, the depih of penetration
and effective treated area were evaluated as described in the section on "Erperinrenlal
Work". Therefore, the retention of different compounds in the ties can also be expressed
on the basis of kg/m3 of lreated area, as shown in Table 5. The equivalent amounts could
not be expressed for the second old (O&) tie, where the penetration of creosote was
observed in the form of circular rings right to the very centre of the tie. Therefore, the
unclear depth of penetration did not enable the calculation of any effective treated area.
The main fact that cornes up from Table 5 is that for al1 the creosote components (except
44
1'' Old Tie 1
kg/m3
0.05
0.02
0.27
1 Fluorene
?40
O. 16
1
Phenanthrene
Anthracene
Fluoranthene
Pyrene Y
Total p henolics
Total retention
0.08
1 .O2
11.70
73.75
12.1 1
0.12
0.08
1.21
1 O0
19.26
3.17
0.03
0.02
0.32
26.1 1
y0
7.00
I 7.50
46.71
9.50
16.63
15.1 1
I .32
1 O0
4.64
28.91
5.88
10.29
9.35
0.82
6 1.89
kg/m3
0.14
kg/m3
n.d
,
n.d.
1.99
Vo
n.d.
0.07 1 3.50 j
n.d.
3 2 2
0.43
0.15
21.50 l
7.50
0.03
0.1 1
1.50
5 5 0
0.07 l 3s0 0.73
0.27
2.00
36.50
13.50
1 O0
the two undetected PAH compounds), the concentration was much higher in the second
new tie than the first new one when it came to retention per unit volume of rreated wood.
4.2 Quantities of PAHs Lost through Various Mechanisrns
42.1 PAH compounds from four different ties:
Since PAHs constitute the major portion of the creosote, most of the analyses
were restricted to the PAH components alone. Moreover, due to reasons cited in the
section on "Experimentaf Work". the analyses were restricted to eight of these
compounds only, namely: naphthalene, acenaphthylene, acenaphthene, fluorene,
phenanthrene. acenaphthene. fluoranthene and pyrene.
The average fluxes per cycle from vaporization, bleeding and leaching are plotted
below for each of the ties in Figures 12, 13, 14 and 15.
e e t ;
LL
--
Figure 12. Comparative rates of loss for 1st New Tie (average of 8 cycles)
Figure 13. Comparative rates of loss for znd New Tie (average of 6 cycles)
-- - - - - - - - - -
Figure 14. Comparative rates of loss for 1" Otd Tie (average of 7 cycles)
Figure 15. Comparative rates of loss for 2nd Old Tie (average of 5 cycles)
A cursory glance at these figures shows that, apart from the fint new tie, leaching
was the predominant loss mechanism for al1 the ties. Vaporization was prominent only in
the case of the first new tie and was surprisingly low for the second new tie. One possible
reason for this low vaporization might be the loss of the compounds from the surface
during storage: the new ties investigated here were stored outside for three years before
they were procured for the experiments, and exposure of the tie surface to a higher
temperature during storage for the second new tie might result in a depletion of the
surface chemicals through vaporization before it was actually used for the expcriment.
High bleeding of fluoranthene, anthracene, and, most importantly, of
phenanthrene from the first new tie are consistent with the high retention of these
compounds in that tie. However, the same may be cxpcctcd for phenanthrene,
fluoranthene and pyrene for the second new tie; but bleeding was altogether negligible in
the second new tie. One possible enplanation for this might be some differencc in
properties (such as porosity) between the two ties. Due to possible difference in moisture
content between the ties, there might be some difference in the ease with which
chemicals from the tie interior were mobilized to become more availablc at the surface of
the first new tie as compared to the second.
4.2.2 Quantities of PAHs leached alter 5 cycles:
The amount of chemicals leached from the four ties averaged over the first five
cycles are ploned in Figure 16. Here again, phenanthrene shows up to be the compound
that is lost most from every tie.
. - - - - -- - -
Figure 16. Leachate flux from each tie (average of 5 cycles)
Fig. 17. on the other hand, shows the leaching with the amounts leached
exprcssed as percentages of initial content in each of the individual ties. The most
prominent fact coming out of Fig. 17 is that percentage leaching from the first old tie is
consistently high for al1 compounds. This is pt-irnarily due to the low retention of most
cornpounds in it, which results in high percentage leaching even for small amounts
leached. Similarly, for the first new tie, the percentage loss of pyrene shows up very high
because of low retention of the compound in the tie.
Fig. 18 shows the percentage of the different compounds of the total PAH loss
through leaching for each of the ties. Here, again, it is seen that phenanthrene accounts
for roughly 50% of the compounds lost through leaching for the tint new tie, whereas
this loss is about 25% for the second new tie and the second old tie.
- . . . . - - A - .
Hlst New O 2nd New O 1st Old
U2nd Old - -- - - - - - - - .
Figure 17. Cumulative percentage leaching from each tie nfter 5 cycles
-- -. - - A - O Pyrene
H Fluoranthene
Ohthracene
H Phenanthrene
Fluorene
OAcenaphthene
Acenaphthyiene
Naphthalene
1st New 2nd New 1st Old 2nd Old
Figure 18. Relative amounts of different compounds leached after 5 cycles
for each tie (amounts added cumulatively after each cycle)
Naphthalene i
::LI- , - . , ;
0 A
3 0.5 1 1
Acenaphthene 1
O 2 4 6 Cycle
+ 1" Ncw Tic
O 2"%w Tic
a 1" Old 'Tic
Acenaphthylene
l O 2 4 6 8
! Cycle
Fluorene
O 2 4 6 8 1
Cycle
Figure 2 1. Cuniulative leaching loss per unit urca of four IDAI-1 coiiiponeiits aftcr cadi cycle for each of t he four tics
Phenanthrene
. 16 +
O 2 4 6 8
Cycle
Fluoranthene
I I .
O 2 4 6 8
Cycle
Anthracene
O 2 4 6 8
Cycle
Pyrene
O 2"" Ncw Tic
A 1 "' Old Tic
0
2"" Old Tic
Figure 22. Cuniulativc leaching loss per unit area of the otlier four l'AH ron~ponents aftcr eiich cycle for crch of the four tics
4.2.3 Progressive leaching of the PAHs:
The amounts of the different PAH components leached afier each cycle were
added cumulatively for each of the four ties. The plots of these cumulative losses of each
of these chemicals at the end of each cycle are presented in Figures 19 and 20. Fig. 19
shows the corresponding plots for naphthalene, acenaphthylene, fluorene and anthracene.
which are leached cornparatively less, whereas Fig. 20 shows the plot for the remaining
four PAH components studied. Figures 19 and 20 show that leaching for most of the
compounds showed a linear trend for the first new tie and for the two old ties. However,
for the second new tie, the leaching of the compounds tended to increase with tirne.
Another means of comparing the leaching patterns between different tics is io
look at the leaching of each individual cornpound in the different ties, as shown in Figs.
2 1 and 22. As these two figures show, for some compounds, more loss is obscrved for the
second new tie than the first one. This was observed mostly for compounds that had
greater retention in the second new tie than in the first one. Other compounds like
phenanthrene that had much greater initial retention in the First new tie were naturally
found to be Iost faster from the first new tie. For fluoranthene, the losses from the first
new tie were extrernely low, and were comparable to the losses from the old ties. This
was logical, keeping in view the low retention of the cornpound in the first new tie.
Before explaining the shapes of the curves, some insight into the leaching
mechanism from the ties would be worthwhile. The leaching may be occumng through
the following paths:
Water i-61' Water PAHs Wood
Transport in 1,~' Transport in water wood
As seen in the above figure. water gets into the pores of the tics during the
leaching cycle, and subsequently takes the compounds out of the tie with it. Thus, the
leaching process in effect consists of two stages, transport inside the wood and transport
in water. The shapes of the curves obtained in Fig. 19 and Fig. 20 depend on which of
these two transport processes is the limiting step. Thus, the curves in Fig. 19 and Fig. 20
can be explained by taking into account the following equations:
If C (moi/m3) is the concentration of any PAH component in the bulk of the water
(leachate) and C, is the concentration at the water-tie interface, then the rate of increase
of concentration is expressed as
where k ( d s ) is the mass transfer coefficient of the chemical in water and t is the
time in sec.
If C' is the concentration of any particular chemical in water within the bulk of
the wood in the tie and Ci be the concentration at the water-tie interface, rate of change
in concentration is
where k' (rn/s) is the mass transfer coefficient of the chemical in wood.
In this case, it should be reasonable to assume that it is water which acts as the
mobilizing medium in the tie as well. Therefore, C,' = C,.
Thus, equation 4 can be re-written as
I t would be worthwhile to study the shapes of the different curves in Figs. 19 to
22 with reference to equation 4 and 5. As seen in these figures, the graphs cûn have either
of the three shapes as follows:
Cumulative Leaching
Time
If leaching is water phase controlled, then the driving force (C,-C) will
continuously decrease, resulting in a continuously decreasing cumulative leaching
concentration. This is represented by curve (a) above.
If C is low enough to be considered negligible compared to C,, and Ci is constant
(equal to the solubility of the chemical in water if the water in wood is saturated), then
where S is the solubility of the chernical in water.
Under the above condition, if leaching is controlling in the water phase, the rate
of leaching is constant. Under such a situation, the cumulative leaching of the chernical
in water folIows the curve (b) above.
The trends obtained for al1 the leached compounds for the two old ties conform to
curve (b). Such a trend can be explained by keeping in view that the concentration in
water for each the compounds were much lower than the respective solubilitics. I t was
only for naphthalene and acenaphthene for the fint new tic that the trend followcd curve
(a). Although the concentration in water was still far below the solubility values for both
these compounds, such a leveling off in the leaching concentrations is the obvious
outcorne of the concentration at the interface (i.e., C,) decreasing over time, resulting in
an overall decrease in the driving force.
If leaching is controiled in wood, then the driving force (C'- C,) should also be
expected to decrease in with time, leading to the condition as depicted in the cuwe (b).
However, a situation may aise, that due io change in the properties of the tie, more and
more chernicals are made available to the surface, leading to a continuous increase in the
dnving force (C'- Ci). This can give rise to the situation in curve (c). Such a curve can
also be obtained if the mass transfer coefficient increases with time, for some probable
change in the properties of the wood.
This is what is observed for all the compounds in the second new tie. This
suggests a major change in the tie property dunng the course of the expenment. There
was a crack on the surface of the second new tie at the begiming of the experiment. With
the different environmental cycles, the crack was found to progressively increase in
width, releasing more cornpounds in the interior of the tie to be exposed to surface water
and be available for loss. With the progressive exposure of fresh treated surface, the
concentration in the bulk of the wood can be expected to increase. This is a possible
explanation of the continuously increasing loss of different compounds from the second
new tic. Moreover, the crack could possibly have accessed the decayed treated zone near
the center of the tie from which loss of the creosote components were casier.
Despite the similarity in trend in the leaching of most compounds from the first
new tie and the two old ties with tirne, the absolute amounts for each individual
cornpound differ drastically among the iies depending upon the initial retentions of the
compound in the ties. For cxample, at the end of five cycles. the absoiute quantities of
phenanthrene lost through leaching were 34.4, 17.9, 8.7 and 6.3 mg respectively for the
first new tie, the second new tie, the first old tie and the second old tie. This can be
compared to the retentions of phenanthrene in the four ties, which were 15.80, 5.83, 0.1 O
and 1.63 kg/mJ of dry wood respectively.
4.2.4 Relating the leaching chiracteristics of the chernicals to different physical-
chernical properties:
The amount of leaching could most likely be positively correlated to either of two
factors: solubility of the components and initial content (retention) of these compounds in
the ties.
a) Correlation between amountsleached and solubility:
As noted above in Section 4.2.3, the cumulative leaching concentration curves
with time can take one of the three possible shapes. For ail the compounds, the leaching
rates were substantially below the solubilities. I t was also noted that apart from the
second new tie. the leaching of the compounds was either constant or decreased with
time. In al1 cases, however, the leachate concentrations were far below the soIubilities for
the compounds. This explains the fact that the rate of leaching for most compounds was
linear for the first new tie and the two oId ties.
First, atternpts were made to find out the leaching rates in relation to solubility.
Figs. 23 to 26 show the corresponding plots for the fours ties. The solubilities of the
different compounds are included in Table 1 in Section 2.6. Naphthalene is not included
in these figures, because the high solubility of naphthalene renden comparison between
the other compounds cxtremely difficult.
O 1 2 3 4 5
Solubility (mglL)
O * 2 2 - I I 9 1.5 - al CI
2 1 P C
Figure 23. Average rate of leaching (pg/cm2.cycle) for 1st New Tie
(Naphthalene not included in this graph)
# 1 1.Naphthalcne 2. Acenaphthylenc 3. Acenaphthene
1 3. Fluorene
3 8 +
4 42
3. Phenrinthrene 6 . Anthracene 7. Fluoranthene 8. Pyrene
1. Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6 . Anthracene 7. Fluonnthene 8. Pyrene
Figure 24. Average rate of leaching (pg/cm2.cycle) for 1st Old Tie
(Naphthalene not included in this graph)
O 1 2 3 4 5
Solubility (rng/L)
Figure 25. Average rate of leaching (pg/cm2.cycle) for 2nd New Tie
(Naphthalene not included in this graph)
Yaphthalenc Xccnaphthylenc Acenaphthene Fluorene Phcnanthrenc Anthncenc Fluorantheno Pyrene
1 . Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene
d 5. Phenanthrene !
' 6 4 2 6. .4nthracene
4 7. Fluonnthene A- J
O 1 2 3 4 5 8. Pyrene
Solubility (rngL)
---
Figure 26. Average rate of leaching (pg/cm2.cycle) for 2nd Old Tie
(Naphthalene not included in this graph)
Figures 23 and 24, which are quite similar in nature, show that most of the
chemicals indicate a lack of dependence on solubility. It can be noted that phenanthrene
(solubility of 1.2 mgL) showed a tendency of substantially higher leaching compared to
its solubility.
The second set of ties shows similar loss patterns in Figures 25 and 26. In these
two figures, the first three chemicals in tenns of solubility do show sorne sort of direct
correlation with solubility, but that correlation ceases to exist with compounds having
solubility 1 .Z mg/L and higher.
Therefore. it may be concluded that the amounts leached from the tics are not a
direct function of solubility. At least, even ifsolubility is one of the factors goveming the
leaching, the correlation is definitely maçked by the effect of other factors.
b) Co rrelatio tt betweetr percentage leaching and soiubiliip
The lack of any evidence of solubility on the amount leached could have been the
effect of masking by some other dominant factor. such as the initial content of these
compounds in the ties. Thus, in order to normalize the effect of the initial contents in the
ties and get better way to find a correlation between soiubility and leaching, the
percentage ieacliing (i.e., amount leached as a fraction of its initial content in the tie) of
different ties were plotted versus solubility. However, no correlation was evident
between the two. Therefore, no correlation whatsoever was found between the amount
leached and the solubilities of the cornpounds.
c) Correlation betweetr arttoun ts leached and initial content (retentiort) :
The amounts leached are ploned as a function of initial content (retention) of
these compounds, as shown in Figs. 27 to 30. The abscissa represents the logarithms of
the initial contents in pg of dry wood. A logarithmic scale was used to accommodate for
the huge variation in the initial contents for various compounds.
I . Naphthalene 2. Acenriphthylenc 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthracene 7. Fluoran~hene Y. Pyrene
5 .O0 6.00 7.00 Y .O0 9 .O0
Log (Initial Content, ug)
Figure 27. Relationship between amount leached (pg) and initial content
(pg dry wood) after 8 cycles for 1st New Tie
Log (Initial content, ug)
LL 10000
UI a - 8000 u œ
5 6000 aJ - $ 4000
s 2000
0
Figure 28. Relationship between amount leached (pg) and initial content
(pg dry wood) after 7 cycles for 1st Old Tie
s* .-
-
*
1 . Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene
a ! 5. Phenanthrene f *6 -8 6. Anthracene
a1 7. Fluoranthene 2 6 a4 - 8. Pyrene
O 6.5 7 7.5 8 8.5
Log (Initial content, ug)
1. Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene 5. P henanthrene 6. Anthracene 7. Fluonnthene 8. Pyrene
Figure 29. Relationship between amount leached (pg) and initial content
(pg dry wood) after 6 cycles for 2nd New Tie
(Naphthalene and acenaphthylene were below limits oldetection for the 2"' New Tie)
O 1 1
6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 7.8
Log (Initial content, ug)
1. Naphthrilene 2. Accnaphthy lenr 3. Acenaphthene 4. Fluorcne 5. Phenanthrene 6. Anthracene 7. F l u o ~ n t h e n c Y. Pyrene
Figure 30. Relationship between amount leached (pg) and initial content
(pg dry wood) after 5 cycles for 2nd Old Tie
(Naphthalene, acenaphthylene and acenaphthene were below limits of detection for the
2"* New Tie)
There is generally a positive correlation between the amount of compounds
leached and the retention of these compounds. This is not tnie for al1 compounds, but the
general trend indicates that the leaching of compounds is much more dependent on the
initial contents of these compounds in the ties, than the solubilities.
Therefore. in conclusion, although some positive correlations can be observed
between retention and the amounts leached, no effect of the solubilities of the individual
components was noted on leaching.
Another factor guiding the loss pattems could be a possible difference in the
distribution of the various components of creosote along the depth of the tie, i.e.. a
distribution gradient from the surface. The losses of the different creosote components
were compared against the amounts of the corresponding compounds in the overall
treated area. But loss pattems are more likely to be related to the creosote component at
the surface. However, such quantifications of the distribution of different creosote
components along the depth of the tie were not perfomed in the present study.
4.2.5 Correlation of the amounts vaporized with different parameters:
a) Correlation beîween amounts vaporized and vapor pressure:
The amounts vaporized are ploned against the vapor pressures as s h o w in the
following figures:
+2 1. Naphthalene
4. Fluorene 5. Phenanthrentl 6 . Anthracene 7. Fluonnthene S. Pyrene
O 0.5 1 1.5
Vripor Pressure (Pa)
Figure 31. Average rate of vaporization (pg/cm'.cycle) for the 1st New Tic
(Nap hthalene not included in this graph due to much higher vapor pressure)
O 2 4 6 8 1 O I ? S.
Vapor Pressure (Pa)
Naphthalene Acenaphthylenc Acenaphthene Fluorene Phenanthrcne Anthracene Fluoranthrine Pyrene
Figure 32. Average rate of vaporization (Iiglcm2.cycle) for the 1st Old Tie
1 . Naphthalene 2. Acenaphthy lene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6 . Anthncene 7. Fluonnthene 8. Pyrene
-- --
Figure 33. Average rate of vaporization (pg/crn2.cycle) for the 2nd New Tie
Figure 34. Average
* 3 1 I . 'laphthalene 2. Acenaphihylene
!
7 3 . Acenaphthene / 4. Fluorene j 5. Phenrinthrenc
6. Xnthmcene 7. Fluoranthene 8. Pyrene *'
V a p o r Prcssurc ( P a )
rate of vaporization (j&cm2.cycle) for the 2nd Old Tie
[t would be natural to assume that the higher the vapor pressure of a compound.
the more would be the vaporization from the tie. However, as observed from Figs. 3 1 to
34, it was only for the first new tie that such an expected trend was by and large
observed. The other ties failed to comply with such an expected trend altogether. One
probable explanation could be that the amounts vaporized are proportional to the vapor
pressure only when it cornes to the vaporization of the compounds at the surface.
Possibly the amount of surface chemicals present was less for the second new tie. due to
exposure to higher surface temperatures during storage.
6) Correlation between percentage loss of initial contents of the compounds th rotigli
vaporization and vapor pressure:
As with the amounts leached, the percentage vaporizdon (i.e., amount vaporized
expressed as a fraction of its initial content in the tie) of each compound was plotted
against the vapor pressure. Therefore, if any correlation between arnounts lost and the
vapor pressure was masked by the different initial contents of the chemicals, the effect of'
vapor pressure would surface through normalizing the vaporized amounts against the
initial contents. However, no such correiation was observed.
Thus. no correlation could be established between the amounts of vaporized
components and any of the physical parameters. One possible explanation is that the
vaporized amounts in absolute quantities (nor the percentage losses though vaporization)
are proportional to the vapor pressure only when the fresh ties have the compounds on
their surfaces (as is observed in the case of most compounds in the first new tie).
c) Correlatiorl betweerr amounts vaporized art d h itial retention:
As with the quantities leached, an atternpt was made to find correlations between
the amounts leached, and the retentions of the cornpounds in the ties. These are plotted
for the first and second new ties (Fig. 35 and Fig. 36) and first old tie (Fig. 37).
LI
m 3 i2i I. Naphthalene
120000 2. Acenaphthylcnc 3 - S 3. Acenaphthene p 80000 , , 4. Fluorene > e E
1 5 . Phenanthrene 6 . Anthracene
a *' 7. Fluoranthene
! 8. Pyrene
OE+OO 1 €+O8 2E+08 3E+08 4E+08 Initial Content (ug)
Figure 35. Amounts (pg) of chemicals vaporized vs. initial content (pg) for
the 1'' New Tie
O.OE+OO 4.OE+07 8.0€+07 1.2E+08 1.6E+08
Initial Content (ug)
1. Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthracene 7. Fluoranthene S. Pyrcne
Figure 36. Amounts (pg) of chemicals vaporized vs. initial content (pg) for
the znd New Tie
1 . Naphthdene 2. XccnaphthyIene 3. Acenriphthene 4. Fluorene 5. Phenanthrene 6. Anthracene 7. Fluoranthene S. Pyrenc
Initiai Content (ug) -- - -
Figure 37. Amounts (pg) of chemicals vaporized vs. initial content (pg) for
the 1" Old Tie
As observed from the above three plots, no clear correlation exists between the
arnounts vaporized and the retention of the compounds in the ties.
4.2.6 Correlation between bleeding and retention:
The factor with which bleeding is most likely to be associated is the retention of
the compounds in the expenmental tie sections. There fore, graphs are plotted show ing the
amounts (pg) of the compounds bled as a function of the amounts (pg/cm2) of the
individual compounds in the two new ties. as shown in Figures 38 and 39.
i . Naphthalene 2. .Acenaphthy Ienc 3. .Acenriphthenc 1. Fluorene 5. Phenanthrent. 6. Anthmccne 7. Fluoranthene S. Pyrcnc
0,00€+00 1.00€+08 2.00E+08 3.00E+08 4.00€+08 Initial Content (ug)
Figure 38. Amounts of chemicals bled (pg/cm2) vs. initial content (pg) of these
chernicals in the 1" New Tie
i
0.0e+00 4.0e+O7 8.Oe+07 1.2e+08 1.6e+08
Initial Content (ug)
1. Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthncene 7. Fluonnthene S. Pyrene
Figure 39. Amounts of chemicals bled (pg/cm2) vs. initial content (pg) of these
chemicals in the 2nd New Tie
As seen from the above two figures, there is a linear relationship between the
amounts of the chernicals bled vs. the corresponding retention in the tie section. The
compounds in the fint new tie fit to a linear trend with a regression coefficient of 0.988,
whereas the corresponding regression coefficient for the second new tie was 0.868.
Such a trend, however, was not observed for the old ties. The first old tie showed
some bleeding only for acenaphthene, anthracene and fluoranthrene, and did not show
any linear trend. As for the second old tie, the only compounds that bled werc
acenaphthene, fluoranthene and pyrene. However, an important point to note is that for
both the ties, acenaphthene was seen to have bled to a much greater extent as compared
to the amounts present. In fact, this was in sharp contrast to expectations, more
particularly for the second new tic, the analysis of which showed the presence of
acenaphthene below the level of detection. 50th the graphs For the old ties could be
plotted only for three points, and it could be acenaphthene that threw the plots out of an
othenvise linear trend. Moreover, since the old ties were both in service for twenty-six
years. the arnount bled was small, so that low levels of the compounds could have
hampered the proper detection of the compounds.
Therefore. taking a11 the above factors into consideration, it can be concluded that
the bleeding of the compounds from the ties are directly proportional to the retention of
the compounds in the ties.
Possible corrclations between the amounts bled and the corresponding melting
points were also investigated, but the plots failed to show any relation between the two.
4.2.7 Possible causes for the lack of correlations of amounts vaporized and leached
with vapor pressure and solubility respectively:
As observed above, no correlation of the amounts of the different chemicals
vaponzed or leached was found with the physical-chemical properties even when the
losses by vaporization or leaching were expressed as a fraction of the initial content in the
ties. One reason behind this could be a variation in the distribution of the different
creosote components dong the depth of the tie. When the losses of the compounds were
expressed as a percentage of the initial contents, the initial contents were calculated on
the basis of the total amounts present in the ties. However, the losses are more likely to
be related to the amounts initially present at the upper layer of the tie, where the crcosote
composition may be different than the overall composition in the tic due to preferentiai
leaching and evaporation of some components during storage (new ties) and in service
(old tics).
A general observation for both vaporization and leaching was that although vapor
pressure as well as solubility for compounds like fluoranthene and pyrene were
sufficiently low. the losses of these compounds were quite high by both these processes.
This can also be explained by a different composition of compounds ai the surface than
the overall composition. For example, the study conducted by Kohler et al. (2000), which
concluded that naphthalene, acenaphthene and fluorene concentrations were far lower at
the layers near the surface than at the middle layers, whereas it was just the reverse for
compounds like fluoranthene and pyrene.
Another reason for the lack of expected correlations of the vaporized and leached
amounts with the physical-chemical properties might be some physical bonding between
the compounds and the wooden tie itself. Wood is composed of complex organic
structures, and the possibility of any physical bonding with these structures with the
organic creosote components cannot be overniled. Such bonding would inhibit the loss of
compounds, even though the vapor pressure or solubility of the compound might be high.
4.3 Phenolic Compounds
The phenolic compounds were calculated and analyzed as total phenolics instead of in
terms of the individual phenolic compounds.
The amounts of the total phenolics iost by the different processes are shown in
Figure ?O. The cornparisons are presented after five cycles for each.
Vaporization Bleeding
. -. - - - --
! O 1 st ~ e w Ti ' : 12nd New Tie
----- l
El lst Old Tie # 0 2nd Old Tie
1
Leaching
Figure 40. Cornparison of losses of phenolic components by different mechanisms
from the four ties
As observed from Fig. 40, apart from the loss by vaporization (which, in fact, was
rather insignificant for a11 the ties), the losses from the first necv tie Far exceeded losses
from the other ties. In fact, for bleeding and leaching, the comparative amounts lost from
the four ties were observed to be proportional to the retentions of phenolics, as seen from
Table 4.
Va porization Bleeding
01 st New Tie
a n d New fie O 1 st Old Tie --- - -
Leaching --
Figure 41. Cornparison of losses of phenolic components (expressed as percentage of
initial contents in the ties) by different mechanisms from three ties
When the losses are plotted as percentages of initial content in the ties (as in Fig.
? I ) , the same picture as Fig. 30 cornes up. The only difference is the higher proportion of
loss from the first old tie, in which the retention of phenolics as such was Iow. The
corresponding bars for the second old tie could not be constructed since the phenolics in
it were below detections limits.
The relative importances of the different loss processes are presented in Figure
47. Here, again, the values are for after five cycles for each tie, in order to facilitate the
cornparison of the values after the same number of cycles for each.
- - - - - .
- D~each ing II Bleeding 6lVaporiza tion - - - - -- - - .
1 st New Tie 2nd New Tie 1 st Old Tie 2nd Old fie - - - - - ---y .
Figure 42. Comparison of the relative importance of the different l o s ~ processes
from the four ties after five cycles for each
As seen in Fig. 42 and 43, leaching is the major loss process for the phenolic
components. In fact, leaching accounted for at least 79% of the loss from al1 the ties. This
is quite natural, keeping in view that phenolic components have high solubilities.
However, the dependence of solubility on the leaching rate could not be studied, as this
requires knowledge of the leaching of the individual phenolic components. For studying
the phenolics, all the phenolic components had to be combined as total phenolics because
the detection of the phenolic components was somewhat inconsistent among the different
cycles. The only compound that showed up relatively consistently was
pentachlorophenol. In fact, wherever appreciable loss of phenolics was noted afier the
first few cycles, the loss mostly comprised of pentachlorophenol alone. This results from
the fact that most treating companies that treat ties with creosote often treat poles and
other products with pentachlorophenol in oil wood preservative using the sarne treating
retort.
As with the PAH components, i t was noted that bleeding of the total phenolics
was also greaier with greater retention in the tie sections.
Figure 43. Cornparison of the relative importance of the different l o s ~ processes
(losses expressed as percentage of initial content) from the four ties after five cycles
'OoYo r' 90%
for each
l:l , * kachhg 6 Bleeding
20% 1 O Vaporization
1 0% fp$$ 0% *%si&
1 st New 7 e 2nd New Te 1st Old Te -- ---
-
80%
70%
60°h
50%
The same picture about the relative importance of the three processes as Figure
42 cornes up in Figure 43 as well, where the ordinate depicts the relative loss expressed
as a fraction of the initial contents in the respective ties.
-
- - - - - - -
- .-
4.4 Comparison between Results of Tie Sections and Small-Scale Laboratory
Experiments
As noted in the section on E-rperiimenfal Work, small-scale laboratory experiments
were conducted under controlled conditions to compare the relative amounts vaporized
and leached with the larger-scale experiments with the tie sections in the Plexiglas
chambers. This was conducted by subjecting a cylindrical plug (drilled out from the first
new tie) to vaporization at 60 "C for four hours and subsequently to leaching for eight
hours,
In this test, naphthalene and acenaphthylene could not be detected in the vapor
phase, probably due to their lower retention in the tie compared to the oiher PAH
components. For these two compounds, as also for fluoranthene and pyrene (both of
which have low vapor pressure), leaching was found to be the only detectable loss
process from the plug.
4.41 Comparison of vaporization and leaching patterns between the plug and the
erperimental tie section of the first new tie:
In Fig. 44, the loss through vaporization per unit area per hour for the lab-scale
experiment is compared to the loss through vaporization from the first new tie section per
unit area per hour over the fint cycle. The general trend of higher losses for the plug
compared to the ties can be explained from the fact that the direct exposure of UV and IR
on the ties was restricted to the upper surface of the tie sections only, whereas for the
plug, the exposure was more uniform over the surface.
In Fig. 45, the corresponding cornparison is s h o w for leaching. Here, the
amounts leached per unit area from the plug were consistently much higher than the
corresponding losses from the first new tie section.
E 1 st New Tie - -
Figure 14. Comparison between vaporization rates ([email protected]) from the plug and
from the lSt New Tie
Such a difference in leaching rates between the plug and the tie section was in
agreement with the findings of other researchers studying the loss of creosote by leaching
from marine piling (as mentioned in Chapter 2), who concluded that the relative loss was
greater with smaller sample size.
. . - - - - - - -
a Plug R 1 st New Tie -- - - - -. ..
Figure 45. Cornparison between leaching rates (pglem'.hr) from the plug and from
the 1st New Tie
As stated above, the rates of vaporization in Fig. 44 were averaged only over
the fint cycle for the first new tie. Keeping in view that vaporization is predominant
only for the first few cycles, whereas leaching continuous even afier several cycles of
exposure, leaching can be cited as the predominant loss mechanism under the conditions
used.
Moreover, the following points came up from the above experiments:
1. More components were visible in significant amounts in the leaching cycle than in
the vaporization cycle.
* .
i l . Unlike vaporization, for both the plug and the first new tie section, considerable
leaching was observed for al1 the high molecular weight compounds.
4.42 Correlation of vaporization with different parameters
As with the tie sections in the Plexiglas chambers. the following correlations were
tried out with the vaporized amounts from the plug. These were as follows:
(a) amounts vaporized (pg/cm') vs. vapor pressure (Pa)
(b) amounts vaporized (pg) vs. initial content (pg)
(c) percentage vaporized (i.e., amounts vaporized as a percentage of initiai content)
vs. vapor pressure (Pa)
As with the experimental tie sections, no correlation was obtained under the
conditions (b) and (c) for the plug. However. as Far as the correlation behveen the
amounts vaporized and vapor pressure is concerned, of al1 the experimental tie sections, it
was only the first new tie that some positive correlation had been observed. Therefore,
the same correlation for the plug is important to study (since the plug is drawn out from
the same tie), and is piotted in Fig. 46.
1. Naphthalene 2. .Acenaphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthracene 7. Fluoranthene 5. Pyrene
Vapor Pressure (Pa)
Figure 46. Amount vaporized (pglcrn2.hr) vs. vapor pressure (Pa) for plug
(Vaporization of naphthalene, acenaphthylene, fiuoranthcne and pyrene not
detected from the plug)
Fig. 46 did not show any positive correlation of the amount vaporized with the
vapor pressure. However, the plot could be constmcted with only four PAH cornponents.
as the other components were below detection limits for the vaporization from the plug.
Of al1 the compounds in the experimental tie section of the first new tie, fluorene (vapor
pressure of 1.3 Pa) was the only compound that did not follow the positive correlation
between amounts vaporized and the vapor pressure. In Fig. 46 as well, it was fluorene
which was against any general positive correlation between the two ordinates of the plot.
Based on the remaining three compounds detected from the vaporized components from
the plug, any conclusion about any correlation of the amounts vaporized with the vapor
pressure would prove inconclusive.
4.4.3 Correlation of leaching with different parameters
As with the expenmental tie sections, the following correlations were attempted:
(a) amounts leached (Icg/crn2) vs. solubility (rng/L)
(b) percentage leached (i.e., amounts leached expressed as a percentage of initial
content) vs. solubility
(c) amounts leached (pg) vs. initial content (pg) in the tie
As with the experirnental tie sections, no correlations were obtained under
categories (a) and (b). For the experimental tie sections, the amounts leached showed a
positive correlation with the initial contents in the ties. The corresponding plot for the
plug is shown in Fig. 47.
Thus, as from the experirnental tie sections, the amounts leached from the plug
also showed a positive correlation with the initial retention of the compounds in the ties.
Therefore, the different observations from the experimental tic sections were
supported by the corresponding data obtained from the controlled lab-scale expenments
with the plug.
5 6 7 8 9
Log (Initial Content, ug)
1. Naphthalene 2. Acsnriphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthncene 7. Fluoranthene 3. Pyrene
Figure 47. Amount leached (pg/cm2.hr) from the plug vs. initial content (pg)
4.5 Cornparison of Total Losses to the Initial Retention
The total amount of the compounds lost by a11 the difkrent rnechanisms after al1 the
cycles were calculated as percentages (by weight) of the initial inventories of the
chemicals in the individual ties. Table 6 represents the cumulative losses after al1 the
cycles for each of the ties (i.e., till the eighth cycles for the first new tic. the seventh cycle
For the fint old tie, the sixth cycle for the second new tie and till the fifth cycle for the
second old tie). Table 7. on the other hand, shows the percentage losses after five cycles
for each tie for better cornpanson among the losses from the ties.
Some of the percentage losses could not be calculated because the initial
retentions of these compounds were below the limits of detection. The weighted
percentage losses were calculated b y mul tipl ying the percentage losses of the individual
components with the fraction of the respective compounds ini tially present in the tie.
One of the major facts that corne out from Table 6 is that despite the several
simulated environmental exposures, the maximum amount of the initial amounts of
chemicals lost from the tie surfaces did not exceed 4% for any of the compounds. In fact,
for most cases, the amounts of the chemicals lost were below 1%, the maximum (3.78%)
being lost from a compound (pyrene) after subjecting a new tie (the first new tic) to eight
fu l l cycles. Therefore, even in the case of a heavily treated new tie, the rate of loss of the
compounds is not extremely high. This indicates that creosote-treated tics retain enough
of the preservative to be effective in fighting decay of the wood even after 25+ years of
application of the creosote.
Table 6. Comparison of total percentage losses and weighted percentage losses from
different ties after al1 the cycles conducted for each of the four ties
1 Fluorene 0.014 1 0.05 0.002 l
znd Old Tie 1'' New Tie 1
ilaphthalene I
Acenaphthy lene
Acenaphthene
2nd New Tie
P henant hrene
1 Total phenolics 1 2.1 1 1 0.004 / 0.77 / 0.010 1 1.25 1 0.171 1 - 1 0 ! 1
1'' Old Tie
Wt.%*
O
O '
%
--
-
%
0.61
0.97
0.05 l l
present in the tie
0.008
0.002
An t hracene
4 / Fluoranthene
Total Loss
The percentage losses from the first old tie far exceeded the Iosses from the
second new tie. and for some compounds, even the first new tie. Without exception, the
weighted loss percentages from the fint old tie were consistently higher for al1
compounds than ail other ties. But this can be attributed to the exceptionally low
quantities of compounds detected in the first old tie, which led to the percentage loss to
be very high in magnitude, although the absolute quantities of chernicals Iost was not that
- 1 O 0.39
I
Wt.%'
0.001
0.00 1
0.035
0.06
2.03
0.04
0.05
* calculatcd by multiplying the percentage losses by the fraction of the corresponding cornpounds initially
0.06 1
0.004
%
- -
0.02
0.003
0.009
0.044
0.10
Wt.%'
O
O
0.009
0.50
1.24
0.5 14
0.003
%
0.02
0.53
b
0.027 '
Wt.%'
0.016
0.19 ' 0.004
1.04
0.1 19
, I I
0.047
0.034
i
0.02
0.056
0.009
0.03 0.002
0.04 0.009 , l
high. The amounts of chemicals lost generally increase with greater residual retention in
the ties.
Table 7. Cornparison of total percentage losses and weighted percentrge losses from
different ties afterfive cycles conducted with each of the four ties
L aphthalene IU Acenap hthy lene I i Acenvphthene
1 Fluorene
/ P henanthrene
( Anthracene
Fluoranthene Ï-- ( Total phenolics
1" New Tie 1 2nd New Tie
% Wt. %' % Wt %'
1" Old Tie 2" Old Tie ' 1 I % Wt %* % Wt.%'
0.20 0.014 - O
* calcuiated by multiplying the percentage Iosses by the fraction of the corresponding compounds initially
present in the tie
Another factor to note is that although the percentage loss as well as absolute loss
was greater for the first old tie, the amounts of residual chernical content in the second
old tie far exceeded the former. This was most likely due to the fact that the chemicals in
the first old tie were retained mostly near the surface, whereas a cross-section of the
second one (made of oak) clearly revealed that penetration was non-uniform, but went to
the very core of the tie. This naturally led to lower losses than the first tie. because losses
are very much related to the amounts of chemicals present on or near the surface.
4.6 Variation dong the Length of the Tie and Comparison with Initial Content
As mentioned in the section on "Experinrental Methods". three cross sections
were sliced from the first new tie section afier exposure to the eight environmental
cycles. These slices were from equally spaced positions dong its lengtb. Analysis of the
three cross-sectional areas provided an indication of the variation in retention of the
different creosote components along the length of the tie. These retention values are
presented in Table 8.
As Table 8 shows, although there was some variation along the length of the tie.
still the relative variations among the different cross-sections analyzed were not
significant for most compounds. Acenaphthylene showed a high relative standard
deviation. But, as already mentioned in Section 3.4, this compound was present in much
lower amounts, whish might contribute to high uncertainties with a slight variation in
analysis.
Comparison of the above retention values with the initial retention of the PAH
components (Table 8) shows good correspondence between initial and final values.
Table 8. Variation in retention (expressed as kg/m3 of dry wood) of creosote
cornponents along the length of the first new tie after being erposed to the
environmentai cycles in Plexiglas chambers
/ Side 1 1 Middle 1 Side 2 1 Average 1 R.S.D. (%) 1 Initial estimate ! 1 Naphthalene
Acenaphthylene i 1
l Fluoranthene 1 0.03 1 0.03 0.02 1 0.03 1 12.2 1 0.03 , 1
I I , i
Acenaphthene
0.04
0.0 1
/ Total 121.88 121.33 / 17.741 20.32 1 11.1 1 21.41 1
0.23
The percentage losses from the various compounds can also be calculated from
Table 8 as well. However, it should be noted in such cornparisons that, in some cases. the
retention of some of the components at some of the three cross-sections analyzed was
higher than their initial retention. This is not unusual, keeping in mind that the losses
afier the different cycles was low compared to the retention of the compounds. Therefore,
it is possible for the slight variation in retention along the length of the tie to overshadow
the differences due to losses from the tie. Therefore, an effort to calculate the percent
losses from Table 8 might not yield a reasonable estimate of the actual value.
0.03
0.01
1 Pyrene 1 0.02
0.21
1 Fluorene 2.76
0.02
0.33 Phenolics
2.50
16.62 Phenanthrene
0.3 1
0.04 1 0.03
0.18
I 1 1.85 1 2.15 1 3.56 1 2.49 1 34.5
17.74
0.02
0.44
0.03
20.0 1 0.04 I l
2.17
1 1.47
2.60 I
I
0.02 58.8
0.2 1
0.02
0.36
0.0 1 1
2.48
15.28
12.7
11.5 1 0.02 1
1 l / I
1
0.22 1 !
12.0
21.9
19.4
2.50
1 5.80
0.26 I 1 !
4.7 Environmental Impact
47.1 PAH compounds - preliminary fugacity model approach:
The environmental impact of the different PAH components from railroad ties can
be studied from two perspectives: first, from the point of view of the final distribution of
each compound in di fferent environmental compartments (air. water. soi1 and sediment),
and secondly, in tems of the tendency of the compounds to bioaccumulate in living
organisms. Moreover, it is also important to judge from the physical properties how much
of the components lost from the ties are expected to Finally end up in the vapor phase and
how much in water. For this purpose, the fugacity-based mass balance model developed
by Mackay (as noted in the Section 2.6) was used.
In order to get a worst-case scenano of the probable environmental impact, the
loss of phenanthrene from the fint new tie was taken into consideration, since
phenanthrene was released from the first new tie in quantities far more than any other
compound from any of the four ties. On the other hand, the tendency of a compound to
bioaccumulate is expressed by its I& value (i.e., the octanol-water partition coefficient),
which represents the concentration of the compound in octanol to that in water in
equilibrium with it. Arnong the eight PAH compounds studied here, fluoranthene has the
highest Kow value (log K& = 5.22). And the amount of fluoranthene in the second new
tie far exceeded the fluoranthene content of al1 the other ties. Therefore, these two
compounds were selected for detailed analysis about the impact on the environment and
the biota, phenanthrene from the first new tie and Buoranthene from the second new tie.
(a) Asstrmptions made in the model calculations:
The chemical input into the model was obtained as follows: The evaluative
environment defined by Mackay considers an area of 1 km by 1 km. Within this area, one
set of two parallel railway tracks of 1 km long is assumed. Considering each tie 9" wide
and the edge to edge distance of 22" between two consecutive ties on the same track, the
total nurnber of ties in such set of hvo tracks in ;\ 1 km stretch was calculated to be 2540.
If each tie to loses the same amount of phenanthrene as from the first new tie per cycle
and the same amount of fluoranthene as from the second new tie per cycle. the total rate
of release of these two compounds to the 1 km2 area can be calculated.
The evaluative environment assumes that 70% of the area is covered by water and
the rest by soil. I t fùrther assumes that under the assumption of unifonn density at
atmospheric pressure, the entire troposphere can be compressed to a height of 6 km. The
near-surface water accessible to pollutants in the short terni is assumed to be 100 rn, as is
the case for oceans. Similarly, most activity in soil and sediment compartments are
assumed to occur at the top 5 cm and 3 cm layers respectively. The details of the model
parameten are as shown in Table 9.
Biodegradation half-lives of 6.7 X 10.' h (Howard et al., 199 1 ) and 2.5 X 10-' h
(Howard et al., 1 99 1) were assumed for phenanthrene and fluoranthene respectively in
water, soil, sediment and suspended sediment, whereas the compounds were assumed to
have a very large persistence (i.e., extremely stable) with extrernely high degradation
half-life values in air and biota. The initial concentrations of the chernicals in air and
waier were considered negligible.
Assuming the quantities of chemicals lost in the experiment per cycle to be the
amounts released in one year, the corresponding rates of losses of the above hvo
chemicals in the evaluative environment were estimated.
Table 9. Specifications of the six-cornpartment evaluntive environment
(Source: Mackay, 199 1. pp: 64 & 139)
Cornpartment Volume (m3) Density (kg/mJ) Composition
Air 6 X 10' 1.2 --
Water 7 X 106 1 O00 --
Soi1 (50% solids, 20% air, 30% water) 4.5 X 10' 1500 2% OC*
Scdiment (37% soIids) 2.1 x IO" 1500 5% OC*
Suspended Sediment 35 1500 16+70h OC*
Aquatic Biota 7 1 O00 5% lipid
Interfacial Areas (mi)
Air- Water : 7 x 1 0 5
Water-Sediment : 7 x los
Soil-Air : 3 x 1 0 5
Inflow rates (m3/h)
Air : 10'
Water : 1000 * OC - Organic Carbon Content
The final concentration of the compounds in water would provide an estimation
about the toxicity potential of the particular chemical to living beings, when compared to
the LCso values of these compounds, as provided by different health organizations. The
toxicity potential of any compound released from the ties can be judged when the model
output in the water is compared to literature citations of the LCjo value for that particular
compound, which represents the concentration of water in which half of the population of
a test species dies.
Mackay's fugacity model is available in different levels with different
assumptions about the system (closed or open) and about equilibrium. In this case, for
simplicity. an open system was assumed for the above purposc where the chernicals are
in equilibrium with each other (referred to as the Level 2 Fugacity Model). In the course
of the experiment, the tie was subjected to temperatures as high as 54 'C and as low as -5
O C . At the same time, during leaching, the experiment was performed at room
temperature. For these reasons, the temperature for the rnodeling purpose was assumed to
be constant at 25 O C (since this model does not allow for the variability of temperature).
Level 2 Fugacity Model is available in two forms: Level 2A and Level ZB. Level
2A considers four environmental compartments: air, water, soi1 and sediment. Level ZB
considers two other phases in addition to the above two, namely: suspended sediment and
biota. In this case, biota is typically represented by fish.
(6) Model outputs:
The mode1 was mn for each of these two compounds using both Level 2A and
Level 2B calculations. The model outputs are provided in Appendix C.
The predicted distributions of these two compounds from each of Level 2A and
Level 2B calculations in the different compartments are tabulated in Table 10. The
predicted loss patterns indicate that the distribution of the compounds in the different
compartments varies widely with the vapour pressure of the compound. Of the two
compounds considered here, phenanthrene has a vapour pressure of 0.0907 Pa, whereas
the vapour pressure of fluoranthene is 6.67 X IO-' Pa. For compounds with relatively
higher volatility, a high proportion ends up in the air compartment, whereas those with
low volatilities end up in the more organic phases like soi1 and sediment, with negligible
concentration in the air compartment. As Table 10 indicates, for phenanthrene, as high as
41% of the compound is ultimately lost to the air compartment. On the other hand, for
fluoranthene (with higher hydrophibicity and much lowcr vapour pressure than
phenanthrene). the corresponding quantity in air is less than 1%, the compound ending up
lost mostly in the soi1 and sediment compartrnents.
Of the other six PAH components analyzed, anthracene and pyrene have vapor
pressures lower than phenanthrene, whereas the rest of the PAH components have higher
vapor pressures. This means that for naphthalene, acentaphthylene, acenaphthene and
fluorene, more than 41% of the compounds lost from the ties are likely to end up in air.
Of these compounds, naphthalene and acenaphthylene were detected in the ties in much
lower quantities than the other PAH components analyzed. At the same time, many of the
PAH compounds in creosote that were not included in the analysis in this experirnent
typically have much lower vapor pressures than phenanthrene. For exarnple, one of' the
least volatile constituents of creosote, benzo[a]pyrene, has a vapor pressure of 7.32 X IO-'
Pa. Considering al1 these Factors, it can be concluded that the ultimate distribution of'
creosote in the different environmental compartments is highly depend on the
composition of the creosote.
However, the differences in implications between the experirnental results and the
mode1 outputs need to be emphasized. The experiments merely show how much of the
compounds were lost by the different processes, whereas the rnodel indicates what
fraction of the cornpoundsfinally end up in the different compartments after partitioning
at equilibrium. In other words, the model output shows the tendency of the different
compounds to end up and be distributed in the different environmental media, which is
entirely independent of the processes (vaporization, leaching or bleeding) by which these
compounds were initiani; lost to the environment.
It should be noted that model outputs for both the compounds showed that only
srnall portions of the compounds ultimately remained in water, whereas there were
appreciable quantities fmally ending up in soil. This impiies that the compounds lost by
leaching ultimately partition into other phases. The tendency to partition into the organic
phases naturally increases with increasing Kow value of the chemical.
(c) Toxicity effects:
Apart from predicting the relative amounts of the chernicals that can be expected
to end up in different environmental media, the model output also indicates the potential
ioxic effect posed by the PM components to living beings. The impact on the biota can
be obtained by comparing the water concentration in the mode1 outputs with the LCso
value of the corresponding chemical. Since LCso values for phenanthrene and
fluoranthene could not be obtained from the literature, the following equation developed
by Konemann (198 1) was used to derive the LCso values of these two chernicals in fish
(guppies) with the knowledge of the respective Kow values:
log llLCso = 0.87 log K o w - 4.87
Although this equation was derived by Konernann specifically for chlorinated
organic compounds, diethyl ether, acetone and glycol denvatives, ii has been used here to
get a rough estimate of the toxicity of phenanthrene and fluoranthene. The LCjo in
equation (7) has the units of pmol/l, so that the values need to be multiplied by the
molecular weight of the respective chemicals and then be divided by 1000 to get the LCjo
values in mg11 (ppm). Using the Kow values of phenanthrene and fluoranthene listed in
Table 1. the LCjo values came out to be 7.5 ppm and 2.1 ppm for phenanthrene and
fluoranthene. These are purely hypothetical values and are even slightly higher than the
respective water solubilities of the two chemicals. but are used here only as a baseline for
comparing the water concentrations in the model outputs with the toxicity of
phenanthrene and fluoranthene.
The model results predicted water concentrations as low as 6 X 10*" ppm and 8 X
10''~ ppm for phenanthrene and fluoranthene respectively for both Level 2A and Level
ZB calculations. This clearly indicated that the water concentrations of the compounds
from the ties in the evaluative environment are far below the levels capable of causing
any potential harm to the surrounding biota.
Moreover, the PAH compounds are also susceptible to biodegradation, making
the effective concentration in the aqueous and organic phases substantially lower than
what the model predicts. Therefore, with the assumptions made in the model, no evidence
of toxicity on biota is predicted within the evaluative environment.
(d) Sensitivity analyses:
Rate of release: One of the basic assumptions in the model inputs was the rate of release
of compounds into the environment. The assumption made above was that each complete
environmental cycle in the expenments in the Plexiglas chambers simuiated one year.
This might not be a very reasonable assumption to get a tme picture of the environmental
effects. Moreover, the model assumes uniform distribution of creosote throughout each
environmental cornpartment. But in reality, the concentrations can be expected to be
much higher in areas closer to the ties. Therefore, to End the validity of making the above
assumption, the Level 2A and Level ZB models were run again for each compound for a
rate of release 100 times the initial assumption (i.e., assuming the amounts released from
100 similar environmental cycles to be the amount released in one year). For such an
increase of input rate, the concentrations in water, as obtained from both Level 2A and
Level 2B model outputs, were 6 X 1 0 ' ~ pprn and 8 X 10"' pprn for phenanthrene and
fluoranthene respectively. This implied that with an iticrease of 100 rimes in the enrission
rate of the compotrnd, the conceniration of the chernical in ivater (and conseqirentiy, in
biota) also increases 100 tintes.
However, since the concentrations in biota even after a hundred-fold increase in
emission rates are still substantially low, the possibility of any potential damage on biota
can be neglected. In fact, it would take emissions many more times in magnitude to cause
any threat to the surrounding biota.
Rate of biodegradation: In the model, the reaction half-lives in water, soil, sediment and
suspended sediment were assumed to be the same and equal to 6.7 X 10-5 h (Howard et
al., 1991) and 2.5 X 10" h (Howard et al., 1991) for phenanthrene and fluoranthene
respectively. To tind the effect of doubling the half-life values (Le., halving the rates of
reaction) in these compartments, Level 2A and Level 2B calculations were performed for
each of these compounds with reaction half-lives of 1.31 X IO-' h and 5.0 X 1oS5 h for
phcnanthrene and fluoranthene respectively. Under such conditions, both Level ZA and
Level 1B calculations yielded concentrations in biota double the previous amounts.
However, even after doubling, the concentration levels were far below the toxic levels.
Thus, in sumrnary, the Level 2 fugacity mode! predicts that alrlioirgh
concert trations in biota double iviih doirbling of irrplrptii rate and also ivith doirblhig o j the
degrcidation ,ales, sirclt concentration levels fiont PA H emissions $mi die ties are jar
beloiv levels caiîsirrg ary potentid danzage to surroundi~ig &iota. Even with an increase
in concentration in water and biota by 100 times, the values were still far below toxicity
limits. Therefore, any possibility of harm to biota from phenanthrene and fluoranthene
released from railway ties may be ruled out. However, it should be borne in mind that for
simplicity, the different compartments were assumed to be in equilibrium with each
other. To get a greater in-depth picture of the environmental fate of the creosote
components, such an assumption cannot be made. Naturally, this would require a more
detailed knowledge about the properties of the chemicals.
4.7.2 Phenolic compounds:
As mentioned in the section on "Introduction", phenolics in water are known to
cause bad taste in fish for human consumption at concentrations of 1-10 mg/l.
(Henningsson, 1983). However, even when al1 the phenolic compounds leached are
considered cumulatively after the eight cycles for the first new tie (where the loss of the
phenoiic compounds was maximum), and even when al1 these cornpounds were supposed
to be retained in the 6 litres of water with which each tie was leached, the total
concentration of the phenolic compounds came to be 0.0175 mgIl. Even if al1 the bled
compounds be assumed to end up in the surrounding water as well? the concentration in
water cornes to 0.021 mg l . Naturally, the conditions at which these concentrations are
calculated make these concentrations much higher than actually attained from these
phenolic compounds in areas adjacent to rail tracks. Even then, these concentrations are
too low to add any bad taste to fish in contamhated water.
Also noted in the section on "Introdrtcrion" is the fact that the suggested phenol
concentration. in order to avoid unacceptable effects on drinking water, is below 0.0001
mgil. But phenol alone represents only a very smatl portion of the total phcnolic
compounds. In fact, although only the total phenolic components were considered in al1
calculations. phenol as an individual compound was below detection limits for al1 the
leaching cycles. At the same time, as noted above, the probable water concentration of
0.0 175 mg/[ for the total phenolics was a great over-estimation of the actual concentration
in water. To add to it is the fact that the phenolic compounds are highly biodegradable.
So, they do not stay in the water in the original form and form degradation products.
Therefore, it can be concluded with adequate confidence that leaching from the chernicals
occurs at levels lower than amounts required to cause any appreciable hann to the
environment. As the different phenolic components have widely varied physical-chernical
properties, a more detailed study of the total phenolics with the fugacity mode1 could not
be performed.
CHAPTER FIVE. CONCLUSIONS
From the expenmental results and their interpretations, the followings can be concluded:
1. Under conditions studied, leaching was found to be the predominant loss process
from al1 the ties. The percentage loss from leaching of the PAHs was the least for
the first new tie. where 50% of the total loss of PAHs was through leaching. For
the other three ties, the percentage of total loss attributed to leaching rangcd
between 86% and 96%.
2. After equivalent number of cycles, the total loss of compounds from the two new
ties was at least double the loss of the corresponding compounds from the old ties.
The rate of leaching for different compounds from the new tics vancd from twice
to ten times the corresponding rates from the old ties. The rate of leaching was
thus found to increase with higher initial amount of the cornpounds in the ties.
3. Leachate concentrations of al1 compounds were far below the corresponding
solubility values in water. For the tint new ties, the rate of leaching decreased
with time for naphthalene and acenaphthene. For the other compounds from the
first new tie, the rate of leaching remained constant throughout al1 the cycles.
However, the rate of leaching of the cornpounds increased with time in the second
new tie, probably due to a gradually enlarging crack on the surface of the tie.
which progressively exposed more cornpounds to the surface. For al1 the
compounds in the two old ties, the rate of leaching was constant with time.
4. The only tie for which appreciable correlation of amounts vaporized was observed
with vapor pressure was the first new tie, which contained the largest initial
largest initial amount of creosote. Apart from that, the rate of vaporization
couid not be correlated to either the vapor pressure or the retention of the
chemicals in the ties. These suggest that volatilization is a major loss process
probably only as long as the compounds last on the surface of the ties.
5. Bleeding is directly related to retention. In most cases, a linear relation was
observed between the amount bled and the initial content of the chemicals in
the ties, particularly for the new ties.
6. Although vaporization and bleeding from the ties brcome negligible after the
initial period in service, Ieaching continues throughout the entire service life
OF the ties. This was clearly observed in the case of the two old ties. where
there was substantial leaching from each of the ties even though the tics used
for experimental purposes were removed from the railway tracks after
twenty-six years of service.
7. After the treatment in the weathering chambers, the observed maximum loss
of the individual compounds was less than 4% of the initial amount in al1 ties.
For most chemicals, even for the new ties, the total percentage loss was less
than 1% of the initial content.
The following estimations were obtained from the Level 2 fugacity model,
which assumes equilibrium between the compartments at 25 O C :
S. Of the total amount of phenanthrene released from the ties, about 40%
should finally be expected to end up in air. The remaining amount is
distnbuted mostly between the soi1 and sediment compartments. For less
volatile compounds Like fluoranthene, most of the chemicals released are
partitioned in the soi1 compartment (about 50%) and the sediment
compartment (about 45%), with negligible amounts in air and other
compartments. This essentially means that the fate of creosote is determined
chiefly by its composition.
The mode1 results also suggested that phenanthrene and fluoranthene
released from the ties would not result in concentrations that are of any
cnvironmental concem. The concentrations in water were predicted to be in
the range of 10-" ppm for phenanthrene and 1 0 " ~ ppm for fluoranthene.
both of which are far below levels that c m cause any potential harm to the
environmen t.
CHAPTER SIX. FUTURE WORK
i. The cntire set of experiments was performed in order to quanti@ the losses of
these compounds from the surface of the ties to the surroundings. But this does
not give the true picture of the effect of these compounds on the environment.
This is particularly tme for the leachates, where biologicnl degradaiion plays a
major role once these organic compounds get into the surface water and
groundwater with the leachates. Thus, the quantities measured in the leachates
give an upper limit of the actual amount that effectively affect the environment.
Therefore. the same leachatc samples should be preserved, and analyzed at
different time intervals to get an idea of the rate of loss of these cornpounds
through biological degradation.
ii. Large peaks were noted on a number of chromatographs at a retention time of
about 21 minutes for the PAHs and of about 19 minutes for the phenolics. The
identity of these peaks could not be matched with any of the peaks in the
standards. One possibility could be that these peaks represent the degradation
product of the two classes of compounds (Le., PAHs and phenolics). Therefore, a
deeper insight into these two peaks might prove quite interesting.
iii. As already mentioned, the Level 2 fugacity model used to determine the fates of
different compounds provides only a rough estimate in understanding the fate of
some of the chemicals in creosote. According to the assumptions inherent in the
Level 2 model used, the fate of the chemicals in the different environmental
cornpartments is independent of the media in which the chemicals are originally
released, because equilibrium is assumed among the different media. However,
with more refined versions of the rnodeI, the amounts released to the different
compartments do have a role to play in determining the fate of the chemicals.
Therefore, instead of considering the total loss of chemicals from the ties as the
input into the system, the loss by volatilization and by leaching can be used to
represent the losses in air and water respectively. This would require a much more
in-depth knowledge of the process parameters. However, problems might still
exist in incorporating the loss from bleeding into these calculations. Yevertheless.
with bettcr knowledge of the process parameters, higher versions of the mode1
would enable better understanding of the fate of the chemicals lost by the different
mechanisrns.
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42. US. EPA. 1984. Coal Tar, Creosote, and Coal Tar Neutra1 Oil Non-wood
Preservative Uses, US. Environmental Protection Agency, Washington, D.C., Report
NO. EPA/540/09-871110.
43. Veith, G. D., Macek, K. i., Petrocelli, S. R. and Caroll, J. 1978. An evaluation of
using partition coefficients and water solubility to estimate bioconcentration factors
for organic chernicals in fish. Proceedings of the 3d Annuai Symposium on Aquatic
Toxicity: 1 16- 130.
44. Verschueren, K. 1996. Handbook of Environmental Data on Organic Chemicals. 2""
edition, Van Nostrand Reinhold, N. Y., U.S.A.
45. von Rurnker, R. E. Lawless and Minersa, A. F. 1975. Case study No. 20. Creosote. ln
Production. Distribution and Environmental Impact Potential for Selected Pesticides.
U.S. Environ. Prot. Agency Rep. No. 540/ 1-74-00 1.
46. Wan. M. T. 1991. Railway right-of-way contaminants in the lower rnainland of
British Columbia: Polycyclic aromatic hydrocarbons. J. Environ. Quai. 20: 228-234.
47. Webb, D. A. 1975. Some environmental aspects of creosote. Proc. Atner. Wood
Preserv. ..lssoc. 1 : 1 76- 1 8 1 .
48. Webb, D. A. 1980. Creosote, its biodegradation and environmental effects. Proc.
Amer. Wood Present. Assoc. 84: 254 - 259.
49. Webb, D. A. and Gjovik, L. R. 1988. Treated wood products and their effect on the
environment. Proc. Amer. Wood Present. Assoc. 84: 254-259.
50. Western Wood Preservers Institute. 2000. http://www.wwpinstitute.or~
51. Windholz, M. (ed.), 1976. The Merck Index - An Encyclopedia of Chemicals and
Drugs. Merck & Co., Inc., Rahway, N.J., 91h Edition.
52. Xiao, Y., Simonsen, J. and Morrell, J. J. 2000. Laboratory simulation of leaching
from creosote treated wood in aquatic exposures. International Research Group on
Wood Preservation. 3 1'' Annual Meeting, Kona, Hawaii, 14"- lgLh May 2000.
APPENDICES
Appendix A. Cross Sectional Views of Different Tie Sections
Cross section of the 1'' New Tie
Cross section of the znd New Tie
Cross section of the 1'' Old Tie
Cross section of the znd Old Tie
1'' New Tie: Adjacent sections of the 1" New Tie: unused part (the one to the left)
and alter 8 environmental cycles (the one to the right)
Penetration along the depth for the three cross sections (the left end, the middle end
and the right end) of the 22-inch section of the 1" New Tie at the end of the cycles
Appendix B. Recommendations for Future Work
There were a few limitations in the experirnental design and set up, as well as in
the analytical procedures adopted. These limitations, and the possible methods to
overcome them in any related future work, are discussed in detail as follows:
1. Design of the experimental chambers
This can be elaborated under the following categories:
a. As already discussed in the section on experimental methods, despite best efforts io
seal the edge of the charnben with silicone, a complete seal could not be achieved.
Therefore, proper construction of the chamber should receive pnmr consideration in
any similar work in future.
In this respect, chambers previously ordered from manufacturers would be a
better plan rather than to construct them in the laboratory from pre-ordered Plexiglas
plates of requisite dimension.
b. Plexiglas did not prove to be the ideal choice of building material for the charnbers.
Plexiglas was chosen primanly to render the conditions inside the charnbers visible
even during operation. Glass was not used in order to keep the system light and to
prevent the chamben from being fragile. But after a considerable number of runs with
the UV-IR cycles, the walls of the chamber were visibly stained with creosote
compounds, as evident from the brown coloration. One possibility to quantify these
compounds absorbed on the walls could have been to wash the walls of the chambers
with the solvent, i.e., methylene chloride. But the solvent instantly melts al1 plastic
products, and hence, could not be used in this case. The situation was apparently
rendered wone because the organic compounds vaporizing from the ties seemed to
have substantial affinity for Plexiglas.
In this regard, two alternatives can be suggested. One of them would be to
reduce the sample size (i.e., use a smaller tie section) and to use glass as the building
rnaterial for the chambers. Glass would still be fragile, but a smaller sample size
would make handling of the chamben more manageable and enable the processes
inside the chamber to be seen from the outside even when in operation. Of course,
any vaporized components sticking to the surface of the glass can be washed oM with
methylene chlonde and included in the quantification of the vaporized components.
However, there is one drawback about using a smaller sample size. As noted by
several researchers, smaller sample size introduces relatively grcater losses of the
components from the wood. The experiment perfonned above with the Plexiglas
chambers was not free of this error either, but a smaller sample size would magnify
this error to a much greater extent.
The other alternative would be to retain the same sarnple size. but use a
chamber made of stainless steel or other suitable metal. Naturally, the walls of such a
chamber can also be washed off with the solvent, and the wash-off can be collected
from a tap dnlled near the corner at the bottom of the metallic chamber. One
drawback with such a metallic charnber would be that the processes inside the
chamber cannot be seen in operation. This, actually, is vital in order to monitor
whether the process is proceeding smoothly or not, for example, whether there is any
blockage at the mouth of the suction line of the pump in the leachate chamber,
resulting in a much lower flow rate through the sprinkler. This drawback can be
overcome by including a glass window at one side of the wall in the design.
2. Unavailability of a method for suitable suction
Ideally, the collection of the vaporized compounds should have consisted of an
inlet for fresh air. and the continuous suction of the outlet air into the solvent traps.
However, no such pump capable of continuous operation over a twenty-four hour period
could be found. In fact, the pump at disposa1 was susceptible to failure for a continuous
operation exceeding thiny minutes due to overheating. Since the time programmer
allowed only six on-and-off cycles per day, the collection of outlet air had to be restricted
to thirty minutes of operation followed by three-and-a-half hours of rest. The inherent
leaks in the system were assumed to be the source of iniet air. This, obviously. was a very
crude approach, but tumed out to be the only way out because of the unavailability of
better equipment. However, it is obvious that in order to make accurate measurements,
one has to have access to better pumps capable of mnning longer on a continuous basis.
Therefore, the three Factors in any similar eapenmental set up for proper
collection of the vaporized compounds would be the availability of leak-proof chambers
having the fiexibility of washing the walls with solvent, as also of a pump capable of
drawing air continuously over extended periods of time.
3. Selection of a better procedure for analyzing the phenolic compounds
Al1 anempts to correlate the different loss processes with the respective physical-
chernical properties of individual compounds (as discussed on the section on Resrclts and
Discicssions) were restncted to PAHs only. This was mostly because the PAHs constitute
the bulk of the creosote components. But a major obstacle in such a correlation for
phenolic compounds was the lack of adequate deteciion for al1 the di fferent phenolic
compounds analyzed. Each of these compounds was present only at very low levels, and
detection over di fferent cycles proved to be extremely inconsistent. There fore, al1 the
di fferent phenolic compounds that were detected for each cycle were added up to get the
total phenolic content.
If such an approach of quantifying only the total phenolics has to be pursued, then
dtogether different methodologies that are available might give better and more accurate
results. These include the techniques used in industrial applications where the color of
adsorbent exposed to suspected phenolic environment is compared to a set of available
standard colon to get a rough idea of the concentration of phenolics in the test
environment. Such methods not only give good results for very low phenolic content, but
also allow the detection of even those phenolic compounds that were no2 present in the
phenolic standard used in the GC.
4. Lack of proper equipment for analysis
The detection of as many as eight of the sixteen different compounds present in
the PAH standard had to be abandoned due to improper detection of their peaks in the
Flame Ionization Detector used for the analyses. One of these high-boiling point
compounds was benzo(a)pyrene, which is highly carcinogenic and hence of considerable
environmental concem. Although present day formulations of creosote are significantly
lower in benzo(a)pyrene, understanding the environmental fate of the compound from old
ties would be a vital part of studies as the present one.
Thus, keeping al1 these facts in view, and, at the same time, for a more efficient
overall analysis, the use of Gas Chromatography with Mass Spectroscopy (GC/MS)
would render the entire process much more efficient as compared to using a GC/FID in
such experiments.
Recommended Construction of an Ideal Chamber for Future Work
Considering al1 the above facts, as also the other factors and observations in the
course of the entire experiment, the following methodolo_ey may be suggested to get the
best possible measure of the different loss processes:
First and foremost, the natural environments have to be simulatcd more
realistically. Of other things, this includes applying the natural environmental effects li ke
the water spray, UV and IR radiations more efticiently. This can be achieved by
mounting the water spray as well as the UV and IR bulbs simultaneously at the ceiling of
the chamber. The real environment can be simulated even better if UV bulbs having
variable wavelengths are used.
Without any doubt, this would require a chamber to be much larger dimensions.
This extra space can be better utilized by including more than one tie in the chamber. In
fact, the full-sized ties rnay also be placed in the chamben instead of the twenty-two inch
sections used in this case. These ties rnay be supported by ballast, just as in the case of
railway tracks in real life. Air can be sucked in constantly from one end of the chamber,
which should ideally be made of steel or some other rnetal having as low affinity for
organic compounds as possible. Such a rnetal would assure that the vaporized cornpounds
are hardly deposited on the walls of the chamber before being drawn out into the traps.
As already mentioned, a small glass window at the side of such a chamber would enablc
the observation of the di fferent processes when in progress. Introducing baffles would
enable an efficient airflow inside the chamber. If the charnber is leak-proof, the
possibility of forcing the air in (as opposed to sucking the air out under the action of
vacuum at the exit) can also be explored.
Bench scale experiments may be conducted to test if there is any detectable
tendcncy of the cornpounds getting adhered to rnetal surfaces at al!. If the observations of
such experiments tum out to on the negative, then there need not be any atternpt to wash
the inside walls with solvent. In case some adherence becornes unavoidable, then it has to
be dealt with differently in the casc of these large metallic chamben, as collecting the
solvent wash-off from the inside walls would hardly be feasible. In that case, one
alternative might be to introduce a layer of some absorbing material (e.g., cotton) on the
inside of the metallic walls. This absorbing material can be held in place by a wire mesh.
and can be removed after each vaporization cycle and extracted with dichloromethane or
some other suitable solvent to quanti@ the chemicals absorbed by it. However, this
would require the chamber to be hinged on one side, so that the charnber can be "opened"
aAer each vaporization cycle and the absorbent be collected.
Thus, the choice of such a suitable absorbing material would be a key factor in
successfully minimizing the underestimation of the vaporized compounds. In fact, if such
a suitable absorbent is found, the entire set of solvent traps at the end of the chamber can
be dispensed with. However, as already stated above, there would be no need of any such
absorbent layer if metal surfaces are found to have little affinity For the compounds of
intercst.
A tap ddled at the bottom of the ballast layer (i.e.. the bottom of the charnber as
such) would enable the collection and/or drainage of al1 the leachate after each leaching
cycle. In order to minimize any water sprinkling on the radiation bulbs, the sprinkler can
be introduced at a much lower level inside the charnber as compared to al1 the radiation
bulbs.
The set up suggested above would, therefore, be a massive undertaking,
somewhat beyond the scope of laboratory-based experiments. But it would have some
added advantages. With the UV and IR bulbs mounted on the ceiling simultaneously, the
e ffects of both these radiations can be studied simultaneously, wi thout IR radiai ion
having to follow the exposure to UV. In fact, as many UV and IR bulbs can be mounted
as desired, giving a uniform radiation effect over the entire bed of ties. The sarne applies
to the water sprays. In fact. such a set up would enable the simultaneous exposures to
radiation as well as to water spray. Thus, the effect of different environmental factors can
be studied either separately or simultaneously, as desired.
There is one major drawback in such a set up. It would be very difficult, if not
impossible, to find the amount of the creosote components that bleed out of the ties.
However, it should be borne in mind that the bled cornpounds either re-solidify on the tie
surface, or they may be lost frorn the surface either through vaporization or through being
washed away by water. Thus, if the ultimate goal for environmental purposes is to
comprehend how much of al1 the compounds arefinally lost as the leachate or with the
vaporized strearn, then there should not be any need to trace back how much of it cornes
Frorn bleeding. The only problem in this case would be the failure to correlate the
vaporized and leached amounts of individual cornpounds with their respective physical-
chernical properties. But although the bled compounds were collected separately in the
experiments actually performed here, no such strong correlation was found in the
experiments actually performed here anyways.
Inflow mol/h 1E-08 Rct halflife h 1E+11 Rct rate c.h-1 6.93E-12 VZ mol/Pa 2420508 Fugacity Pa 4.401785E-15 Conc mol/m3 1.775759E-18 Conc g/m3 3.165112E-16 Conc ug/g 2.67005E-13 Amount mol 1.065455E-08 Amount % 41.08635 D rct mol/Pa. h 1.677412E-05 D adv rnol/Pa.h 4034.179 Rct rate mol/h 7.383605E-20 Adv rate rnol/h 1.775759E-11 Reaction % 4.672576E-14 Advection % 1.123756E-05
Total advection D value 4108.407 Total reaction D value 3,589907E+10 Total D value 3.589907E+10 Total chemical input mol/h 1,5802E-04 Total chemical output mol/h 1.5802E-04 O u t p u t b y r e a c t i o n mol/h 1.5802E-04 Output by advection mol/h 1.800432E-11
Overall residence time h 1.641064E-04 Reaction residence time h 1.641064E-04 Advection residence time h 1433.954
Lcvcl28 calculations for Phenanthrcnc
PROGRAM 'LEVEL2B1:SIX COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Phenanthrene
Temperature deg C Molecular rnass g/mol Vapor pressure Pa Solubility g/m3 Solubility mol/ni3 Henry's iaw constant Pa.m3/rnol Log octanol-water p-coefficient Octanol-water partn-coefficient Organic C-water ptn-coefficient Air-water partition coefficient Soil-water partition coefficient Sedt-water partition coefficient
Emission rate of chemical mol/h .O0016 Fugacity Pa 4.398776E-15 Total of VZ products 5894570 Total amount of chemical mol 2.592889E- 08
Phase properties,compositions and rates
Phase Air Volume m3 6E+09 Density kg/m3 1.185413 Frn org carb O Zmol/rn3.Pa 4.034179E-04 Adv.flow m3/h 1E+07 Adv.restime h 600 Inf.con.mol/rn3 1E-15 Inflow mol/h iE-08 Rct halflife h I E - t l l Rct rate c.h-1 6.933-12
Water 7000000 1000 O 7.422817E- 1000 7000 1E- 11 1 E - 08 . O00067 10343.28
Soi 1 45000 1500
. O2 02 33.92142
O O O O . O00067 10343 -28
Sediment 21000 1500 . O 4 6 7 . 8 4 2 8 5 O O O O . O00067 10343.28
Susp sedt 3 5 1500 . O4 67.84285 O O O O . O00067 10343.28
Fish 7 1000 O 132-3763 O O O O 1E+11 6.93E-12
vz mol/Pa 2420508 519597.2 1526464 1424700 Fugacity Pa 4.398776E-15 4.398776E-15 4.398776E-15 4.398776E-15 Conc rnol/rn3 1.774545E-18 3.265131E-16 1.492127E-13 2.984255E-13 Conc g/m3 3.1629493-16 5.819769E-14 2.659568E-11 5.319135E-11 Conc ug/g 2.668225E-13 5.819769E-14 1.773045E-11 3,54609E-11 Amount: mol 1.064727E-08 2.285591E-09 6.714573E-09 6.266935E-09 Amount % 41.06334 8.814845 25.89611 24.1697 D rct mol/~a.h 1.67741?&-05 5.374342E+09 1.578865E+10 1.473608Et10 D adv mol/~a.h 4034.179 74.22817 O O Rct rate mol/h 7.378558E-20 2.364052E-05 6.945073E-05 6.482068E-05 Adv rate mol/h 1.774545E-11 3.265131E-13 O O Reaction % 4.669383E-14 14.96046 43.9506 4 1.02056 Advection % 1.1229873-05 2.066277B-07 O O
Total advection D value 4108.407 Total reaction D value 3.592363E+10 Total D value 3.592363E+10 Total chemical input mol/h 1.5802E-04 Total chemical output rnol/h 1.5802E-04 Outputby reaction mol/h 1.5802E-04 Output by advection mol/h 1.807196E-11
Overall residence time h 1.640861E-04 Reaction residence time h 1.640861E-04 Advection residence time h 1434.758
VZ mol/Pa 2420508 519597. 2 1526464 Fugacity Pa 4.456946E-13 4.456946E-13 4.456946E-13 Conc mol/m3 1.798012E-16 3.308309E-14 1.511859E-11 Conc g/m3 3.204776E-14 5.896731E-12 2.694738E-09 Conc ug/g 2.703509E-11 5.896731E-12 1.796492E-09 Amount mol 1.078807E-06 2.315817E-07 6.803367E-07 Amount % 41.08635 8.819785 25.91062 D rct rnol/Pa.h 1.677412E-05 5.374342E+09 1.578865E+10 D adv rnol/Pa. h 4034.179 74.22817 O Rct rate mol/h 7.476133E-18 2.395315E-03 7.036916E-03 Adv rate rnol/h 1.798012E-09 3.308318-11 O Reaction % 4.672577E- 14 14.9707 43.98067 Advection % 1.123756E-05 2.067691E-07 O
Total advection D value 4108,407 Total reaction D value 3.589907E+10 Total D value 3.589907E+10 Total chernical input mol/h 1.600002E-02 Total chemical output mol/h 1.600002E-02 Outputbyreaction mol/h 1.600002E-02 Output by advection mol/h 1.831095E-09
Overall residence time h 1.641064E-04 Reaction residence time h 1.641065E-04 Advection residence time h 1433.954
Sensitivity analysis with errrissiur~ rate for Phenanthrene (Lcvel 28)
PROGRAM 'LEVEL2B1:SIX COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Phenanthrene
Temperature deg C 25 Molecular mass g/rnol 178.24 Vapor pressure Pa . 0907 Solubility g/m3 1.2 Solubility mol/m3 6.732496E-03 Henry's law constant Pa.m3/mol 13.47197 Log octanol-water p-coefficient 4.57 Octanol-water partn-coefficient 37153.54 Organic C-water ptn-coefficient 15232.35 Air-water partition coefficient 5.434835E-03 Soil-water partition coefficient 456.9885 Sedt-water partition coefficient 913.9771
Emission rate of chemical mol/h .O16 Fugacity Pa 4.453898E-13 Total of VZ products 5894570 Total amount of chernical mol 2.625382E-06
Phase properties,compositions and rates
Fhase Air Wa ter Volume m3 6E+09 7000000 Density kg/m3 1.185413 1000 Frn org carb O O Z m o l / r n 3 . P a 4.034179E-04 7.422817E-02 Adv.Elow m 3 / h 1E+07 1000 Adv.restime h 600 7000 Inf.con.mol/m3 1E-15 1E-11 Inflow mol/h I E - O ~ I E - O ~
Soi 1 45000 1500 . O2 33.92142 O O O O
Sedinieri t 21000 1500 . O 4 67.84285 O O O O
Susp sedt 3 5 1500 . O 4 67.84285 O O O O
Fish 7 1000 O 132.3763 O O O O
Rct halflife h 1E+l1 Rct rate c.h-1 6.93E-12 VZ mol/Pa 2420508 Fugacity Pa 4.453898E-13 Conc mol/m3 1.7967823-16 Conc g/m3 3.202585E-14 Conc ug/g 2.7016613-11 Amoun t mo 1 1.078069E-06 Amoun t 3 41.06334 D rct mol/Pa.h 1.677412E-05 D adv mol/Pa.h 4034.179 Rct rate mol/h 7.471022E-18 Adv rate mol/h 1.796782E-09 Reaction % 4.669382E-14 Advection 3 1.1229873-05
Total advection D value Total reaction D value Total D value Total chemical input mol/h Total chemical output mol/h Output by reaction mol/h Output by advection mol/h
Overall residence time h Reaction residence time h Advection residence time h 1434.758
4 N 4 -3' O 4 vl O N 0 0 m O O N m m o m w r ( - m o o o o
VZ mol/Pa Fugacity Pa Conc rnol/m3 Conc g/m3 Conc ug/g Amount mol Amount % D rct mol/Pa.h D adv mol/~a.h Rct rate niol/h Adv rate mol/h Reaction % Advection %
Total advection D value 4108,407 Total reaction D value 1.794953E+10 Total D value 1.794954E+10 Total chemical input mol/h 1.5802E-04 Total chemical output mol/h 1.5802E-04 Output by reaction mol/h 1.580199E-04 Output by advection mol/h 3,616865E-11
Overall residence time h 3.282129E-04 Reaction residence time h 3.282129E-04 Advection residence time h 1433.954
Sensitivity analysis with degrudutiotr rate for Phcninthrcne (Lcvcl 2B)
PROGRAM 'LEVEL2B1:SIX COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Phenanthrene
Temperature deg C Molecular mass g/rnol Vapor pressure Pa Solubility g/m3 Solubility mol/m3 Henry's Law constant Pa.m3/mol Log octaxiol-water p-coefficient Octanol-water partn-coefficient Organic C-water ptn-coefficient Air-water partition coefficient Soil-water partition coefficient Sedt-water partition coefficient
Emission rate of chemical mol/h Fugacity Pa Total of VZ products Total amount of chemical mol
Phase properties,compositions and rates
Phase A i r Volume m3 6 E + 0 9 Density kg/m3 1 . 1 8 5 4 1 3 Frn org carb O Z mol/rn3.Pa 4 . 0 3 4 1 7 9 E - 0 4 Adv.flow m3/h 1 E + 0 7 Adv,restime h 6 0 0 Inf.con.mol/m3 1 E - 1 5 Inflow mol/h 1E-08 Rct halflife h 1 E + 1 1
Water 7 0 0 0 0 0 0 1 0 0 0 O 7 . 4 2 2 0 1 7 E - 0 2 1 0 0 0 7 0 0 0 1 E - 1 1 1 E - 0 8 . O00134
Sediment 2 1 0 0 0 1 5 0 0 .O4 6 7 . 8 4 2 8 5 O O O O . O00134
Susp sedt: 3 5 1 5 0 0 .O4 67.84285 O O O O . O00134
Fish 7 1 0 0 0 O 132.3763 O O O O 1 E t 1 1
Rct rate c . h - 1 6 . 9 3 E - 1 2 VZ mol/Pa 2420508 Fugacity Pa 8 . 7 9 7 5 5 B - 1 5 Conc mol/rn3 3 .549089E-18 Conc g/m3 6 . 3 2 5 8 9 7 ~ - 1 6 Conc ug/g 5 . 3 3 6 4 4 9 E - 1 3 Amoun t mo 1 2 . 1 2 9 4 5 3 E - 0 8 Amount % 4 1 . 0 6 3 3 4 D rct rnol/Pa,h 1 . 6 7 7 4 1 2 E - 0 5 D adv rnol/Pa. h 4 0 3 4 . 1 7 9 Rct rate mol/h 1 . 4 7 5 7 1 1 3 - 1 9 Adv rate mol/h 3 . 5 4 9 0 8 9 E - 1 1 Reaction % 9 . 3 3 8 7 6 5 E - 1 4 Advection % 2 . 2 4 5 9 7 5 E - 0 5
Total advection D value 4108.407 Total reaction D value 1 . 7 9 6 1 8 1 E + 1 0 Total D value 1 . 7 9 6 1 8 2 3 + 1 0 Total chernical input mol/h 1 . 5 8 0 2 E - 0 4 Total chernical output mol/h 1 . 5 8 0 2 E - 0 4 Outputbyreaction mol/h 1.5801993-04 Output by advection mol/h 3 , 6 1 4 3 9 2 E - 1 1
Overall residence time h 3 . 2 8 1 7 2 3 E - 0 4 Reaction residence t i m e h 3 . 2 8 1 7 2 3 E - 0 4 Advection residence tinie h 1434.758
aJ \O c, O w Lrl a O a N 3 O \O d o 7 0 0
VZ mol/Pa 2420508 Fugacity Pa 2.11438E-18 Conc mol/m3 8.529787E-22 Conc g/m3 1.725576E- 19 Conc ug/g 1.455675E- 16 Amoun t mol 5.117872E- 12 Amoun t 3 -6759208 D rct mol/~a.h 1.677412E-05 D adv mol/Pa.h 4034,179 Rct rate rnol/h 3.546686E-23 Adv rate mol/h 8.529787E-15 Reaction % 1.701302E- 16 Advection % 4.091634E-08
Total advection D value Total reaction D value Total D value Total chemical input rnol/h Total chemical output mol/h Output by reaction mol/h Output by advection mol/h
Overall residence time h Reaction residence time h Advection residence time h
Lcvel2B Calculations for Fluoranthenc
PROGRAM 'LEVEL2B0:SIX COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Fluoranthene
Temperature deg C 25 Molecular mass g/mol 202.3 Vapor pressure Pa . 000667 Solubility g/m3 .26 Solubility mol/m3 1.28522E-03 Henry's law constant Pa.m3/mol .5189773 Log octanol-water p-coefficient 5.22 Octanol-water partn-coefficient 165958.6 Organic C-water ptn-coefficient 68043.03 Air-water partition coefficient 2.093647E-04 Soil-water partition coefficient 2041.291 Sedt-water partition coefficient 4082.582
Emission rate of chemical mol/h 2.OE-05 Fugacity Pa 2.112744E-18 Total of VZ products 3,58488E+08 Total amount of chemical mol 7.5739358-10
Phase properties,compositions and rates
Phase Air Water Volume m3 6E+09 7000000 Density kg/rn3 1.185413 1000 Frn org carb O O 2 mol/m3.Pa 4.034179E-04 1.926866 Adv-flow m3/h 1E+07 1000 Adv.restirne h 600 7000 lnf.con.mol/m3 1E-15 1E-11 Inflow mol/h 1E-O8 1E- 0 8 Rct halflife h 1E+11 . 000025 Rct rate c.h-1 6.93E-12 27720
Soi l 45000 1500 . O2 3933.295 O O O O . O00025 27720
Sediment 21000 1500 . O 4 7866.59 O O O O . O00025 27720
Susp s e d t 3 s 1500 . O4 7866.59 O O O O .O00025 27720
F i s h 7 1000 O 15349.44 O O O O 1Etll 6.93E-12
VZ mol/Pa Fugacity Pa Conc mol/m3 Conc g/m3 Conc ug/g Amount mol Amount % D xct rnol/Pa.h D adv mol/Pa.h Rct rate mol/h Adv rate rnol/h Reaction % Advection %
Total advection D value Total reaction D value Total D value Total chemical input mol/h Total cheniical output mol/h Output by reactian rnol/h Output by advectiori mol/h
Overall residence time h Reaction residence time h Advection residence time h
m r r E E a 1 - - E U \ k m m t u r c \ w U l i V a c E E 0 4 - 4
P l X U - 4 E O A m 3 u ' X D E O ~ E ~ ~
al u k \ 4 QJ 0 3 ru al E - 4 O d w k U O S m - ~ m a . . - 4
Rct rate c,h-1 6.93E-12 VZ mol/~a 2420508 Fugacity Pa 2,028504E-16 Conc mol/m3 8.103349E-20 Conc g/m3 1.655491~-17 Conc ug/g 1.396552E-14 Amoun t mol 4.910009E-10 Amount % .6759207 D rct mol/Pa.h 1.677412E-05 D adv mol/Pa.h 4034.179 Rct rate mol/h 3.402637E-21 Adv rate mol/h 8.183349E-13 Reaction % 1.701301E-16 Advection % 4.091634E-08
Total advection D value 5961.046 Total reaction D value 9.859582E+12 Total D value 9.859582E-+12 Total chemical input rnol/h 2.00002E-03 Total chemical output rnol/h 2.00002E-03 Output by reaction mol/h 2.00002E-03 Output by advection mol/h 1.2092E-12
Overall residence time h 3.632053E-05 Reaction residence time h 3.632053E-05 Advection wesidence time h 60074.23
Seiisitivity analysis with c~~iissiuir rate for Fluorantticne (Level2B)
PROGRAM 'LEVEL2B1:S1X COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Fluoranthene
Temperature deg C Molecular rnass g/mol Vapor pressure Pa Solubility g/m3 Solubility mol / rn3 Henry's law constant Pa.m3/rnol Log octanol-water p-coefficient Octanol-water partn-coefficient Organic C-water ptn-coefficient Air-water partition coefficient Soil-water partition coefficient Sedt-water partition coefficient
Emission rate of chemical mol/h .O02 Fugacity Pa 2.026935E-16 Total of VZ products 3.58488&+08 Total amount of chernical mol 7.266318E-08
Phase properties,compositions and rates
Phase A i r Volume m3 6E+09 Density kg/m3 1.185413 Frn org carb O Z mol/rn3.Pa 4.034179E-04 Adv.flow m3/h 1E+07 Adv.restime h 600 Inf.con.mol/rn3 1E-15 Inflow rnol/h 1E-08 Rct halflife h 1E+11
Water 7000000 1000 O 1.926866 1000 7000 1E-11 1E-08 . O00025
Soi 1 45000 1500 .O2 3933.295 O O O O . O00025
Sedirnent 21000 1500 .O4 7866.59 O O O O .O00025
Susp sedt 35 1500 . O 4 7866.59 O O O O . O00025
Rct rate c . h - 1 6 . 9 3 E - 1 2 VZ mol/Pa 2420508 Fugacity Pa 2 . 0 2 6 9 3 5 E - 1 6 Concmol/m3 8 . 1 7 7 0 1 0 E - 2 0 Conc g/m3 1 . 6 5 4 2 1 1 E - 1 7 Conc ug/g 1 . 3 9 5 4 7 2 E - 14 Amount m o l 4 . 9 0 6 2 1 1 E - 1 0 Amount % . 6 7 5 1 9 9 1 D rct mol/Pa.h 1 . 6 7 7 4 1 2 E - 0 5 D adv mol/Pa.h 4 0 3 4 . 1 7 9 R c t rate mol/h 3 . 4 0 0 0 0 4 E - 2 1 Adv rate rnol/h 8 , 1 7 7 0 1 8 3 - 1 3 Reaction % 1 . 6 9 9 9 8 5 E - 1 6 Advection % 4 . 0 8 8 4 6 8 3 - 0 8
Total advection D value 5 9 6 1 . 0 4 6 Total reaction D value 9 . 8 6 7 2 1 4 E + 1 2 Total D value 9 . 8 6 7 2 1 4 E + 1 2 Total chemical input rnol/h 2 . 0 0 0 0 2 E - 0 3 Total chemical output mol/h 2 . 0 0 0 0 2 E - 0 3 Output by reaction mol/h 2 . 0 0 0 0 2 E - 0 3 Output by advection mol/h 1 , 2 0 8 2 6 5 E - 1 2
Overall residence time h 3 . 6 3 3 1 2 3 E - 0 5 Reaction residence time h 3 . 6 3 3 1 2 3 E - 0 5 Advection residence t i m e h 6 0 1 3 8 . 4 4
Rct rate c . h - 1 6 . 9 3 E - 1 2 vz mol/Pa 2420508 Fugacity Pa 4 . 2 2 8 7 5 9 E - 1 8 Conc rnol/m3 1 . 7 0 5 9 5 7 E - 2 1 Conc g/m3 3 . 4 5 1 1 5 2 3 - 1 9 Conc ug/g 2 . 9 1 1 3 4 9 3 - 1 6 Amoun t mol 1 . 0 2 3 5 7 4 1 - 1 1 Amount % , 6759208 D rct mol/Pa. h 1 . 6 7 7 4 1 2 E - 0 5 D adv mol/Pa.h 4 0 3 4 . 1 7 9 Rct rate rnol/h 7 . 0 9 3 3 7 2 E - 2 3 Adv rate rnol/h 1 . 7 0 5 9 5 7 E - 1 4 Reaction % 3 . 4 0 2 6 0 3 E - 1 6 Advection % 8,183267E-O8
Total advection D value Total reaction D value Total D value Total chernical input mol/h Total chernical output mol/h Output by reaction mol/h Output by advection mol/h
Overall residence tirne h Reaction residence time h Advection residence time h 6 0 0 7 4 . 2 2
Sensitivity analysis with degradation rate for Fluoranthene (Level 2B)
PROGRAM 'LEVEL2B':SIX COMPARTMENT FUGACITY LEVEL II CALCULATION
Properties of Fluoranthene
Temperature deg C 25 Molecular mass g/mol 202.3 Vapor pressure Pa . 000667 Solubility g/m3 .26 Solubility mol/m3 1.28522E-O3 Henry's law constant Pa.rn3/mol .5189773 Log octanol-water p-coefficient 5.22 Octanol-water partn-coefficient 165958.6 Organic C-water ptn-coefficient 68043.03 Air-water partition coefficient 2.093647E-04 Soil-water partition coefficient 2041.291 Sedt-water partition coefficient 4082.582
Ernission rate of chemical mol/h 2.OE-05 Fugacity Pa 4.225488E-18 Total of VZ products 3.58488E+08 Total amount of chernical mol 1.514787E-09
Phase properties,compositions and rates
Phase Air Volume m3 6E+09 Density kg/rn3 1.185413 Frn org carb O Z mol/m3. Pa 4.034179E-04 Adv.flow m3/h 1E+07 Adv.restime h 600 Inf.con.mol/rn3 1E-15 Inflow mol/h 1E-08 Rct halflife h 1E+ll
Water 7000000 1000 O 1.926866 1000 7000 1E-11 1E-08 . O0005
Soi 1 45000 1500 . O2 3933.295 O O O O .O0005
Sediment 21000 1500 . O4 7866.59 O O O O . O0005
Susp sedt 3 5 1500
.O4 7866.59 O O O O . O0005
Fish 7 1000 O 15349.44 O O O O 1E+11
Rct rate c.h-1 6.93E-12 VZ mol/Pa 2420508 Fugacity Pa 4.225488E-18 Conc mol/m3 1.704638E-21 Conc g/m3 3.448482E- 19 Conc ug/g 2.909097E-16 Amount mol 1.022783E-11 Amount % ,675199 D rct mol/~a.h 1.677412E-05 D adv rnol/Pa.h 4034.179 Rct rate mol/h 7.087884E-23 Adv rate mol/h 1.704638E-14 Reaction % 3.39997B-16 Advection % 0.1769363-08
Total advection D value Total reaction D value Total D value Total chemical input mal/h Total chemical output mol/h Outputby reaction mol/h Output by advection mol/h
Overall residence time h Reaction residence time h Advection residence time h 60138.45
