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Chemical Geology 199 (2003) 53–70

Stable lead isotopes, contaminant metals and radionuclides in

upper Hudson River sediment cores: implications for improved

time stratigraphy and transport processes

Steven N. Chillruda,*, Sidney Hemminga, Edward L. Shusterb, H. James Simpsona,Richard F. Boppb, James M. Rossa, Dee C. Pedersona, Damon A. Chakyb,

Lael-Ruth Tolleyb, Frank Estabrooksc

aLamont–Doherty Earth Observatory of Columbia University, Rt 9W, Palisades, NY 10964, USAbEarth and Environmental Sciences, RPI, Troy, NY 12180, USA

cNYS Department of Environmental Conservation, 50 Wolf Road, Albany, NY, USA

Received 17 April 2002; accepted 7 February 2003

Abstract

Radionuclide, stable lead isotope and trace metal analyses on fine-grained sediment cores collected along a 24-mile reach of

the upper Hudson River were used to establish temporal trends of contaminant loadings, to establish stable lead isotopes as an

additional stratigraphic tool, and as tracers for resolving particle transport fluxes over periods of decades. Very large contaminant

inputs of Cd, Sb, Pb and Cr were evident in the sediment record. One potential large source for these metals was from a pigment

manufacturing facility in Glens Falls, NY. The total range in stable lead isotope ratios observed in well-dated cores from about 15

miles downstream of the potential metal inputs was large (e.g., maximum difference in 206Pb/207Pb is 10%) and characterized by

four major shifts occurring in the 1950s, 1960s, 1970s and 1980s. The temporal trend in 206Pb/207Pb has been used to establish

precise dating of a sediment core from 24 miles further downstream. The large magnitude and abrupt shifts in stable lead isotope

ratios preserved in upper Hudson sediment cores provide a way to significantly improve dating models, based only on

radionuclide analyses. Cadmium, lead and antimony were identified as quite sensitive tracers of upper Hudson sediments due to

the magnitude of contamination and the lack of significant additional downstream sources of these contaminant metals. Metal

measurements in a pair of sediment cores located 24 miles apart were used to constrain relative fluxes of sediment entering the

river between the two coring locations, with sediment sections deposited between the early 1960s and the late 1970s in these two

cores suggesting that 3–4 times more sediment entered the river between the two coring sites than was transported from

upstream. These dilution factors agree very well with estimates based on suspended sediment measurements during a flood event

in April 1994 and with estimates based on mechanistic model of suspended sediment transport between 1977 and 1992.

D 2003 Elsevier Science B.V. All rights reserved.

Keywords: Stable lead isotopes; Hudson River sediments; Metals; Radionuclides; Stratigraphy; Contaminant transport

0009-2541/03/$ - see front matter D 2003 Elsevier Science B.V. All right

doi:10.1016/S0009-2541(03)00055-X

* Corresponding author. Tel.: +1-845-365-8893; fax: +1-845-

365-8155.

E-mail address: [email protected] (S.N. Chillrud).

1. Introduction

Contamination of sediments and fish with poly-

chlorinated biphenyls (PCBs) along more than 200

s reserved.

S.N. Chillrud et al. / Chemical Geology 199 (2003) 53–7054

miles of the Hudson River has greatly influenced

public policies of this river/estuary system since the

1970s. Large-scale dredging of some of the most

contaminated sediments is one option under consid-

eration for sites that are relatively near the original

PCB discharges from two capacitor manufacturing

facilities. In addition to PCBs, upper Hudson River

sediments are highly contaminated with several met-

als. This complex mixture of contaminants could

possibly limit disposal/reclamation options, as well

as influence legal responsibility issues. It is important

to characterize the distribution and transport processes

related to the entire suite of contaminants in Hudson

River sediments in order to develop sound manage-

ment plans for the system.

In this paper we have three major objectives:

(1) document temporal trends in metal levels and

stable-lead isotope composition in fine-grained

sediment cores along a 24-mile stretch of the

upper Hudson River;

(2) develop the use of stable lead isotopes as an

additional stratigraphic tool in upper Hudson

River sediments which is a new application in

this region; and

(3) develop a simple empirical budget model for

calculating relative amounts of fine-grained sedi-

ment fluxes that have entered the Hudson between

coring locations, based upon observed metal

concentrations in paired sediment cores which

have been dated using combined radionuclide plus

stable lead isotope time stratigraphies.

Whereas all three objectives are specifically related

to contaminant management issues in the upper Hud-

son River, the third objective provides a methodolog-

ical approach to estimate relative sediment fluxes

which could potentially be used in other river systems

that have received large discrete influxes of particle-

reactive contaminants. Fine-grained sediment fluxes

can often be difficult to assess directly since data have

not been commonly collected for many downstream

sediment sources.

1.1. Radiogenic lead isotopes

Lead ore bodies have varying Pb isotope ratios that

reflect the U/Pb and Th/Pb ratios and ages of their Pb

sources, as well as the ore formation ages. Very old

ores, such as those from Broken Hill, Australia (ca.

2� 109 years) contain small amounts of radiogenic Pb

isotopes (Gulson et al., 1985), while younger ores

derived from high U/Pb sources, such as those mined

in several regions of Missouri (ca. 2.5� 108 years)

have much higher proportions of 206Pb, 207Pb, and208Pb relative to 204Pb. This range in stable Pb

isotopic composition has been exploited in numerous

studies of sources of lead to the environment, from

urban centers to relatively pristine settings (Chow and

Johnstone, 1965; Simpson and Catanzaro, 1978;

Elbaz-Poulichet et al., 1986; Sturges and Barrie,

1987; Maring et al., 1987; Hamelin et al., 1989;

Keinonen, 1992; Mukai et al., 1993; Farmer et al.,

1996; Rosman et al., 1997; Weiss et al., 1999, among

others). Lead isotopes have also provided sensitive

tracers of Pb sources in blood (Manton, 1977; Rabi-

nowitz, 1987, 1995), sediment (Shirahata and Wong,

1981; Hirao, 1986), soils (Rabinowitz, 1989, 1995)

water (Stukas and Wong, 1980), and paint (Rabino-

witz, 1987, 1995).

Although environmental studies have primarily

reported 206Pb/207Pb ratios, additional information

can be obtained from other Pb isotope ratios. 208Pb

derives from the decay of 232Th, whereas 206Pb and207Pb derive from decay of 238U and 235U, respectively,

so that variations in U/Th ratios of Pb sources to ores, as

well as their formation age, influence the ratio of 208Pb

to the other Pb isotopes. North American ores have lead

isotope ratios which differ by as much as 6–25%,

depending on the isotope ratio (Doe and Delavaux,

1972; Heyl et al., 1974; Doe, 1975; Sverjensky et al.,

1979a,b; Sverjensky, 1981; Hart et al., 1981; Fletcher

and Farquhar, 1982a,b; Deloule et al., 1986). Since

these ratios can be measured with a precision (2r) ofV 0.05% per atomic mass unit (amu) by mass spec-

trometry, stable lead isotopes can be especially sensi-

tive tracers. For example, the ratio of maximum

potential signal to measurement precision is between

ca. 500 for 206Pb/207Pb and 60 for 207Pb/204Pb.

In addition to permitting deconvolution of multi-

ple sources of environmental lead, stable Pb isotope

ratios can potentially provide sensitive time strati-

graphic information. Simpson and Catanzaro (1978)

reported predictions made by Claire Patterson that206Pb/207Pb isotope ratios measured in environmental

samples from the USA would increase from around

S.N. Chillrud et al. / Chemical Geology 199 (2003) 53–70 55

1.15 in the 1950s and 1960s to 1.35 in the 1970s,

due to shifts in sources of lead ore. By the 1970s,

less ore was extracted from mines in the northwest

(low 206Pb/207Pb) and more ore from mines located

in the Midwest (high 206Pb/207Pb). Observed tempo-

ral trends in environmental samples reflect an

upward shift in 206Pb/207Pb during the 1960s to

1970s although not as large as that predicted by

Patterson (Rosman et al., 1994; Marcontionio et al.,

2002). Hurst et al. (1996) exploited this temporal

trend in Pb isotopes to establish the timing of leaks

of leaded gasoline from underground tanks and to

estimate the age of depth sections of sediment cores.

Marcontionio et al. (2000) observed temporal trends

in 206Pb/207Pb ratios in Chesapeake Bay sediments

that were in excellent agreement with those observed

in Bermuda corals (Shen and Boyle, 1987).

Here, we report detailed chronologies of radio-

nuclides, metals, and stable lead isotope ratios derived

from fine-grained sediment cores collected from along

a 24-mile reach of the upper Hudson River.

1.2. Radionuclide dating of riverine sediments

Approximate dates of particle accumulation were

assigned to individual depth sections of sediment cores

based on depth distributions of 137Cs and 7Be. Cesium-

137 from global fallout produced measurable activities

in sediments around 1954 and reached a maximum in

1963 (Ritchie andMacHenry, 1990).Measuring detect-

able activities of 7Be in the upper layers of a sediment

core provides another constraint on the most recent

history of particle accumulation at a particular site.

Beryllium-7 is a particle-reactive cosmogenic radio-

nuclide, produced in the atmosphere, that has a radio-

active half-life of 53 days; consequently, the presence

of 7Be at measurable levels in a core section indicates

that a portion of that sediment either accumulated

within 6 months to a year prior to collection of the

core or was physically or biologically mixed into the

section. As an initial approximation, a constant rate of

particle-mass deposition was assumed between pairs of

radionuclide time stratigraphic indicators (earliest pres-

ence of 137Cs, maximum activity of 137Cs, and meas-

urable 7Be in core top section). First-order rates of

accumulation can thus be assigned by simply multi-

plying the mean sedimentation rate by the sample

depth. Accumulation rates can be independently esti-

mated using each pair of these three sediment horizon

layers, providing a first-order indication of variability

of sedimentation rates throughout a core.

Uncertainties sometimes associated with the above

approach to assigning ages to sediment layers include:

coring artifacts, diffusion of dissolved 137Cs in pore

waters, or bioturbation (see Crusius and Anderson,

1991 and references therein). These uncertainties

generally appear to be minor in areas of the Hudson

River with relatively rapid sedimentation rates as

supported by the following observations. Beryllium-

7 has been observed in a substantial fraction of our

core tops without measurable activity in sections

below, indicating recent particle accumulation and

lack of sediment mixing. Diffusion of 137Cs in upper

Hudson sediment samples is probably very limited

since Hudson sediments have relatively high clay

content and low porosities compared to values typical

of many lakes and fresh water is only present. The

average weight percent solids in surficial Hudson

sediments is about 40–50% compared to values

typical of lake sediments of 2–10%. Compaction of

the upper layers of sediments relative to deeper layers

during coring is also much less important than for

most lakes because Hudson sediments have lower

porosities. Effects of bioturbation on estimates of

mean sediment accumulation rates appear to be min-

imal for Hudson River sites with sedimentation rates

z 1 cm/year (Olsen et al., 1981a).

Cesium-137 has previously been used to estimate

sedimentation rates for many cores from the Hudson

River and estuary (Simpson et al., 1976; Bopp, 1979;

Bopp et al., 1981, 1982, 1993; Olsen et al., 1981b;

Bush et al., 1987; Bopp and Simpson, 1989). 210Pb

has not been used very frequently in river systems due

to relatively low excess 210Pb activities in most

riverine sediments (Beasley et al., 1986; Bush et al.,

1987; W. Schell, personal communication, 1994).

2. Experimental

Sediment samples discussed here were collected

from fresh water reaches of the Hudson River water-

shed. Locations along the Hudson River are generally

referred to the number of statute miles upstream of the

southern tip of Manhattan. The Green Island Dam

bounds the upstream limit of tidal currents in the


Hudson River (Fig. 1). The main stem of the river

upstream of the Green Island Dam is often referred to as

the ‘‘upper Hudson,’’ which contains a series of eight

dams and associated navigational locks. The sediment

core collected furthest upstream (site mp 188.5) was

obtained by hand coring on 19 July 1983 in ca. 0.6 m of

water, several meters upstream of the Thompson Island

Dam. In 1991 and 1992, additional hand cores were

collected from the same site. Avibra core was collected

at a water depth of 1 m on 31 July 1997 at site mp

163.6V, approximately 400 m upstream of Lock 2, near

the eastern shore. The vibra core, designed by NYS

Department of Environmental Conservation, consisted

of a vibrating head with a core tube attached directly to

the head (i.e., no core catcher, no metal sleeve, etc.).

Core 169.0Awas collected by hand coring on Decem-

ber 7, 1995 in approximately 1 m of water, near the east

shore of the Hudson River approximately 1 mile

upstream of the Stillwater (Lock 4) dam. The inner

Fig. 1. Map of Upper Hudson River Watershed. Locations of major

point sources of metals (pigment plant) and PCBs (two capacitor

plants) were both upstream of a large dam that was removed in 1973

(formerly Ft. Edward Dam). Coring sites mp 188.5, mp 169.0A and

mp 163.6V are also marked.

diameter of the polybutyrate liners used for all of these

cores was 5.65 cm.

Sediments were air-dried in an incubator oven (35

jC) over a number of days using a flow of air that had

passed through a column of magnesium silicate (flo-

risil), which had been previously heated to 450 jC, toreduce the possibility of atmospheric contamination

by chlorinated hydrocarbons during the drying proc-

ess. Dry sediment samples were ground to a fine

powder with a mortar and pestle, homogenized by

hand and then sealed in air-tight, 100-ml enamel-lined

aluminum cans or 4-ml plastic vials for radionuclide

analysis. Measurement of 137Cs and other gamma-

emitting radionuclides were made using either an

intrinsic germanium or a lithium-drifted germanium

detector. Reported activities were decay-corrected to

the date of sediment core collection, unless otherwise

stated. One-gram subsamples were digested with a

mixture of strong acids (HNO3, HF, HClO4, HCl) for

trace metal analysis following the procedures of

Fleisher and Anderson (1991). The acid solutions

were analyzed for trace metals by atomic absorption

spectrometry and/or inductively coupled plasma mass

spectrometry (VG PQ2+). Precision and accuracy of

trace metal analytical results by the above methods,

based on measurements of replicate digests of sedi-

ment standards and samples, were < 5% for most of

the metals and < 10% for all of the metals.

Stable Pb isotope analyses were made by thermal

ionization mass spectrometry (TIMS) and by magne-

tic-sector, high-resolution, inductively coupled plasma

mass spectrometry (HR-ICP-MS). TIMS analyses

were run on a VG sector 54-30 mass spectrometer

at Lamont–Doherty Earth Observatory in static mode,

following standard procedures (Cameron et al., 1969).

Ratios were corrected for cup bias and mass fractio-

nation as determined with reference material from the

National Bureau of Standards (NBS 981). Typical

external measurement reproducibility (defined as

twice the relative standard deviation (2RSD)) of

NBS 981 by TIMS run at LDEO was 0.031% for206Pb/207Pb. HR-ICP-MS analyses were performed on

a Finnigan ElementR equipped with a guard elec-

trode. Data were collected on masses 203, 205, 206,

207, and 208; 205Tl/203Tl was used for mass bias

correction. The instrument was carefully tuned for

signal stability and the flattest possible peaks at the

start of every day. For each sample, 1800 electrostatic


scans of 0.205 s were done, with the magnet set at

mass 203. Data were acquired on the middle 10% of

each peak. In order to avoid dead time corrections and

to improve counting statistics, the analog detector was

used. Samples were diluted to obtain ca. 5 to 25� 106

counts per second (cps) for each isotope, correspond-

ing to absolute Tl and Pb concentrations in solutions

between 5 and 25 ng/ml. Samples were free-aspirated

with a micro-concentric nebulizer and passed through

an uncooled Scott-type spray chamber. NBS 981 was

Fig. 2. (A) Inter-comparison of 206Pb/207Pb in Hudson River sediments

precision-based analysis of NBS 981 (see text). Heavy line is a least squar

two measurement techniques. (B) Inter-comparison of 208Pb/206Pb in Huds

shown are F 2r precision-based analysis of NBS 981 (see text).

run repeatedly during each day to monitor instrument

and mass bias fractionation stability. Each Tl-mass

bias corrected sample ratio was subsequently cor-

rected by a factor consisting of the true NBS 981

ratio divided by the average of that day’s Tl-corrected

NBS 981 ratios. The external measurement precision

of this method, as defined by 2RSD of repeated

analyses of the Pb isotope standard NBS 981 (73

analyses done over 6 days), was 0.07% for the206Pb/207Pb and 0.1% for the 208Pb/206Pb. These

analyzed by TIMS and HR-ICP-MS. Error bars shown are F 2re fit to the observations. Thin line assumes a 1:1 relationship for the

on River sediments analyzed by TIMS and HR-ICP-MS. Error bars


precision values obtained by HR-ICP-MS are approx-

imately twice the value for the precision by the LDEO

TIMS. Sediment samples run by TIMS and HR-ICP-

MS give excellent agreement in 206Pb/207Pb and208Pb/206Pb ratios (Fig. 2). Lead-204 was not moni-

tored in the HR-ICP-MS runs and so inter-compar-

isons cannot be made for ratios relative to 204Pb.

3. Results and discussion

The radionuclide, lead isotope and trace metal data

are provided for all three cores in six ancillary tables

(see Appendix A) that can be accessed via the internet

at Chemical Geology.

3.1. Sediment dating

For coring sites mp 188.5 and mp 163.6V, depth

profiles of 137Cs (Fig. 3A,B) are indicative of semi-

continuous sediment accumulation over the last few

decades. The depth profile of 137Cs for coring site mp

169.0 (Fig. 3C) may be indicative of accumulation of

sediments over the last couple of decades, but is

probably not consistent with semi-continuous sediment

Fig. 3. (A) Depth profiles of 137Cs and Total PCBs (data from McNulty, 19

(B) Depth profile of 137Cs in a sediment core collected on 31 July 1997 from137Cs in a sediment core collected on 7 December 1995 from site 169.0

counting statistics in all three figures.

accumulation since the mid-1950s (see discussion

below).

For mp 188.5, linear interpolations between 137Cs

and 7Be horizon layers demonstrate that a single

sedimentation rate of 1.2 cm/year is consistent with

the timing of all three of the marker horizons (i.e., 7Be

in core top, maximum 137Cs activity, and first pres-

ence of 137Cs) in core 188.5. However, in core mp

188.5, there is a plateau in 137Cs activities, nearer to

the surface than the maximum in 137Cs (see Fig. 3A),

which we interpret as probably reflecting large sedi-

ment transport event(s) initiated by the removal of the

Ft. Edward Dam in 1973 and continued by high spring

discharges in 1974 and 1976 (Bopp et al., 1985). Such

an interpretation suggests the possibility of at least

three sedimentation rates instead of the model of a

single rate: core top to plateau (1.3 cm/year), plateau

(2.7 cm/year), and 1.0 cm/year for both the interval

between the plateau and the 137Cs maximum and the

segment between the 137Cs maximum to the earliest

presence of 137Cs.

For site mp 163.6V (Fig. 3B), two distinct sed-

imentation rates were derived between the pairs of

horizon layers identified by 7Be and 137Cs: core top to137Cs maximum (1.59 cm/year) and 137Cs peak to first

97) in a sediment core collected on 19 July 1983 from site mp 188.5.

site 163.6V. Note different scales on both axes. (C) Depth profile of

A. Note different scales on both axes. Error bars for 137Cs are 2r


presence of 137Cs (4.44 cm/year). The large change is

sedimentation rate is surprising; however, these sed-

imentation rates are consistent with two additional

secondary features of the 137Cs depth profile of this

core. The sedimentation rate of 1.59 cm/year places

the small shoulder or plateau in 137Cs activities,

located at 32–40 cm, as having accumulated in

1973–1976, consistent with being associated with

the ‘‘dam removal event’’ discussed above. The sed-

imentation rate of 4.44 cm/year places the horizon

layer containing a secondary 137Cs peak located at

76–84 cm as being associated with fallout immedi-

ately prior to the moratorium in atmospheric testing

signed in 1958. For sediment cores with accumulation

rates V 2 cm/year, the observation of this secondary137Cs peak is expected to be unusual since the 4-cm

segments at which most of our cores are sectioned

obscures this feature.

For core mp 169.0A (Fig. 3C), two distinct sed-

imentation rates are derived between pairs of horizon

layers: core top to 137Cs maximum (0.8 cm/year) and137Cs maximum to first presence of 137Cs (V 0.2 cm/

year). The abrupt change in sedimentation rate ob-

tained for this core is a potential flag that normal

radionuclide dating may not be appropriate in this

case. Furthermore, the depth profile of 137Cs does not

have the correct appearance to be reflecting semi-

continuous accumulation of fine-grained sediments.

One major difficulty with the 137Cs depth profile is the

abrupt decline in 137Cs activity from the two sections

(24–28 cm and 28–32 cm) that displayed the max-

imum 137Cs activities for the core and the section

immediately below that had no significant 137Cs

activity. In addition, the maximum 137Cs activities in

this core (2100 pCi/kg) seem too low to represent the

period of maximum fallout in the early mid-1960s

based upon other cores collected within this 24 mile

reach of the upper Hudson River. This can be illus-

trated by comparing the ratio in a particular core of the

maximum activity of 137Cs to the 137Cs activity in the

core top section (Rpk/top). The value for Rpk/top for core

mp 169.0A is 4.8, which is much lower than the

values for core mp 188.5 (19.7) and core mp 163.6V

(17.3). It is possible that both of these apparent

deficiencies in the depth profile (low maximum activ-

ity and very sharp decline in 137Cs activity below the

maximum) could be partially explained by how the

core was sectioned in 4-cm slices. On the other hand,

it is also possible that these apparent deficiencies

reflect a hiatus in the record, caused either by an

erosion or dredging episode immediately prior to

accumulation of the 28–32 cm depth section. In the

discussion below the stable lead isotope data strongly

indicates that a hiatus in sedimentation exists in core

169.0A and provides evidence on the timing of the

hiatus. With only the radionuclide depth profiles, the

interpretation of the time stratigraphy of core mp

169.0A would be very ambiguous.

3.2. Stable lead isotope evidence for contaminant

sources

The Pb isotope compositions of samples from core

mp 188.5 lie on linear trends on plots of 207Pb/204Pb

and 208Pb/204Pb vs. 206Pb/204Pb (Fig. 4A,B). Inter-

mediate compositions cannot be distinguished from

natural sediments as represented by Ordovician shales

of NewYork (Bock et al., 1998) on plots of 207Pb/204Pb

vs. 206Pb/204Pb (Fig. 4A). However, the line defined by

mp 188.5 data clearly does not pass through the Or-

dovician shale data on the 208Pb/204Pb vs. 206Pb/204Pb

plot (Fig. 4B). The isotope compositions of commonly

used ore deposits are also shown in Fig. 4A,B. The data

from site mp 188.5 could be explained as mixing

between ore sources from SE Missouri and from

Balmat, NY. Balmat is a much smaller mine, but is

nearby and plausibly could have been a Pb source for

the pigment factory. However, Balmat NY is not the

only mine with lead ores having lower isotope ratios

that are consistent with the upper Hudson data. For

example, lead isotope ratios of galenas from ore

deposits and formations in westernMontana and north-

ern Idaho (Marvin et al., 1984) are also consistent with

the linear trends defined by the upper Hudson data.

Varved clay samples were obtained from a sedi-

ment core collected upstream of the Thompson Island

Dam. The core contained dark brown, fine-grained,137Cs bearing sediments overlying banded gray clays

without significant activities of 137Cs. These banded

gray (varved) clays were probably deposited during

glacial times and thus provide us with estimates of Pb

isotope ratios in uncontaminated fine-grained sedi-

ments of the area. Two sections of this varved clay

were analyzed and had 206Pb/207Pb ratios of 1.209,

within the range of values measured for Ordovician

shales in NY (Bock et al., 1998). Only the most recent

Fig. 5. Temporal trends of 206Pb/207Pb in three cores. In panel (A),

depth sections are assigned approximate dates of deposition based

only on radionuclide data. Samples from coring site mp 188.5 are

shown as squares, with open squares being the top 2 cm of a core

collected in 1992 and the filled squares being all the sections of a

core collected in 1983. Circles display data for core 163.6V

collected in 1997. Open triangles display data for core mp 169.0A

collected in 1995. The 206Pb/207Pb temporal trend for core mp

169.0A as reconstructed from the radionuclide data alone is not

consistent with the temporal trends observed in the other cores. (B)

Temporal trends of 206Pb/207Pb in three cores, with approximate

dates of deposition based on both radionuclide and stable lead

isotope data. As compared to the dates assigned in panel (A), no

changes in assigned dates were made to core mp 188.5, minor

changes were made to assigned dates of certain sections of core mp

163.6V, and major changes were made to assigned dates of several

sections of core mp 169.0A.

Fig. 4. Plots of 207Pb/204Pb vs. 206Pb/204Pb (A) and 208Pb/204Pb vs.206Pb/204Pb (B). Data from site mp 188.5 (open circles) and isotope

compositions of commonly used ore deposits and Ordovician shales

of New York are also shown (see text for citations).


sediments from the upper Hudson River approach this

value, indicating that contaminant inputs have prob-

ably controlled stable Pb isotope ratios in bulk sedi-

ments over the entire 40-year period considered here.

3.3. Stable lead isotope stratigraphy

The temporal trend of 206Pb/207Pb is dramatic in

upper Hudson sediments, displaying four large shifts

over four decades (Fig. 5A). The total increase in206Pb/207Pb during the 1960s and 1970s is ca. 10%.

This change is very large compared to those

observed in other locations for environmental sam-

ples which have integrated multiple sources of Pb

inputs (e.g., Shen and Boyle, 1987; Graney et al.,


1995; Marcontionio et al., 2002), where the typical

increase during the 1960s and 1970s was ca. 1–2%.

The large magnitude of the observed shifts in stable

Pb isotope ratios together with the high Pb concen-

trations in these sediments (discussed below) sug-

gests that a single manufacturing facility could have

dominated Pb inputs into this reach of the upper

Hudson River. If several large and independent

sources contributed, then different temporal patterns

of purchasing, use, or delivery to the river system

would probably have significantly decreased the

magnitude of stable Pb isotope changes observed

in the sediment cores.

Stable Pb isotope ratios of cores mp 188.5 and mp

163.6V, collected 24 miles apart, are almost identical

for almost all of the time that these sediment cores

represent (Fig. 5A). The similarity of 206Pb/207Pb

between the two cores confirms the radionuclide

dating model of core mp 163.6V (i.e., that in the

mid-1960s there was a large change in sedimentation

rate for this core). More importantly, the similarity of206Pb/207Pb between the two cores over the last few

decades indicates that depth profiles of stable Pb

isotopes can be used as an additional time strati-

graphic tool in upper Hudson sediment cores. The

time periods of the late-1950s to mid-1960s and the

mid-1970s to mid-1980s are those during which the

lead isotope ratios are most anomalous (as compared

to background values described above). Except for the

mid-1960s, the 137Cs dating method provides only

interpolated dates during these periods when stable

lead isotopes provide additional information. Conse-

quently, stable Pb isotope depth profiles provide

powerful new stratigraphic markers in upper Hudson

sediments during extensive time periods when the137Cs method can provide only interpolated dates.

Downcore variations in lead isotope ratios can

permit correlations between sediment cores to be better

constrained. Well established dates are critical for

studies of in situ processes based on paired sediment

cores such as determining in situ dechlorination rates

(Chillrud, 1996; McNulty, 1997). For example, in Fig.

5A, the 206Pb/207Pb temporal trend based on radio-

nuclide-derived dates suggests that beginning in the

mid-1970s, interpolated dates for core mp 163.6V

appear to be displaced later in time by about 3 years

as compared to core mp 188.5. Since measurable

activities of 7Be (activity >2r counting error) fix the

date of the core top of core mp 188.5, the ‘‘error’’ or

displacement in assigned dates interpolated from radio-

nuclides is probably mostly in the mp 163.6V core.

Core mp 169.0A provides a more dramatic exam-

ple of the utility of Pb isotopes as a stratigraphic tool

in upper Hudson sediments. The temporal trend for206Pb/207Pb for core mp 169.0A that is derived from

the age model provided by its 137Cs depth profile (Fig.

5A) is clearly inconsistent with Pb isotope stratigra-

phy derived from cores mp 188.5 and mp 163.6V. As

discussed above, the 137Cs depth profile for 169.0A

suggested a possible hiatus in sedimentation occurring

prior to the 28–32 cm depth section. The 206Pb/207Pb

ratios confirm this tentative interpretation of a hiatus

and also allow estimation of the time period of

accumulation for the depth sections above the hiatus.

Sediments at this site that contain significant activities

of 137Cs appear to have accumulated since the early

1980s (Fig. 5B).

3.4. Trace metal concentrations

Core mp 188.5 has very high activities of 137Cs and

very high concentrations of Cd, Cr, Sb, Pb and Zn (Fig.

6, Appendix A). The 137Cs activities of sediments

collected upstream of the Thompson Island Dam are

the highest reported for Hudson River sediments

(Chillrud, 1996). Maximum enrichment factors for

trace metals (maximum concentration in core divided

by concentration of uncontaminated fine-grained sedi-

ments (Table 1)) in this upstream core range from < 10

(Cu), to between 1 to 2 orders of magnitude (Cr, Sn, Zn

and Pb), to greater than 2 orders of magnitude (Sb and

Cd).

Concentrations of Cu, Pb and Sb display a strong

tendency to follow Cd concentrations in the upstream

core (r2 = 0.92, 0.90, 0.66, respectively), while the

temporal trends of Zn and Sn are distinct from Cd and

the other trace metals. The strong correlations be-

tween Cd and Cu, Pb and Sb suggest that they

probably share input history and/or transport mecha-

nisms. Thus, one or more of them can be used to trace

the downstream transport of contaminated sediments.

The sensitivity of a particular metal as a transport

tracer depends on its contaminant enrichment factor

and the relative strength of downstream sources.

Based on these criteria, Cd appears to be the most

sensitive tracer (Table 1), followed by Sb. Lead

Fig. 6. Temporal trends of 137Cs, Cd, Sb, Pb, Cu, Sn, Zn and Ag in sediments from site mp 188.5 and mp 163.6V. Approximate year of

deposition is based on combined radionuclide and stable Pb isotope stratigraphy. From site mp 188.5: core top collected in 1992 (open square)

and core collected in 1983 (filled square). From site mp 163.6V: core collected in 1997 (open circle with center dot). In (A), Cs-137* denotes

that both cores have their 137Cs activities decay-corrected to the same date (31 July 1997).


concentrations are somewhat less promising due to

likely diffuse sources downstream (e.g., road run-off

and atmospheric deposition throughout the Hudson

Table 1

Estimates for concentrations of metals in uncontaminated fine-grained sed

Ag (Ag/g) Cd (Ag/g) Cu (Ag/g)

Background estimates

Varved claysa 0.06, 0.15 0.13, 0.14 24, 24

NY harbor b 0.5 25

Average shalec 0.1 0.3 45

Tributary inputs based on sediment core measurements (Range of measur

Batten Kill Riverd 0.3–1.8 0.6–1.0 32–48

Hoosic Riverd 0.6–4.6 1.0–1.8 32–48

a Measurements made on two varved clay samples collected below Thb Chillrud (1996).c Turekian and Wedepohl (1961), Marowsky and Wedepohl (1971).d Chillrud (unpublished data).

drainage basin). However, diffuse sources of Pb do

not appear to be sufficient to significantly alter the Pb

isotope compositions between the two cores. As

iments and tributary sediments

Pb (Ag/g) Sb (Ag/g) Sn (Ag/g) Zn (Ag/g)

34, 34 0.08, 0.09 1.8, 1.8 73, 83

20 80

20 0.2 6 95

ements shown below)

31–54 1.0–16.7 2.7–7.5 170–1300

45–74 0.6–3.0 4.9–9.8 110–170

ompson Island Pool sediments.


discussed above, stable Pb isotope ratios of cores mp

188.5 and mp 163.6V collected 24 miles apart are

nearly identical for most of the time that these sedi-

ment cores represent (Fig. 5A). This similar temporal

trend suggests that there have been relatively insig-

nificant sources of Pb to the river between these two

coring locations or that any downstream source had

similar Pb isotope compositions through time as to

those found upstream. Downstream sediment trans-

port and dilution from inputs of relatively clean sedi-

ments (with respect to Pb) must account for the

differences in concentrations seen between the two

cores. Cu is a less suitable tracer because it is not so

highly enriched in upstream sediments.

For a number of persistent, particle-reactive con-

taminants including 137Cs and most metals, a large

downstream concentration gradient exists between

cores mp 188.5 and mp 163.6V, consistent with the

upstream core being closer to the likely input sources.

Potential causes of the higher 137Cs activities found in

core mp 188.5 has been discussed elsewhere (Chillrud,

1996) and is not the focus of this paper. One potential

source of metals located several miles upstream of site

mp 188.5 is a pigment factory (Fig. 1) that has operated

since the early 1900s. A compilation of 1982 metal

discharges into the Hudson basin, based on New York

State Department of Environmental Conservation dis-

charge permits and associated discharge data, reported

that this manufacturing facility was the largest single

point source in the basin (excluding the NYC metro-

politan area) of Pb, Cd, and hexavalent Cr, with

estimated discharges in 1982 of more than 4.5 kg/day

for Pb and between 0.45 and 4.5 kg/day for both Cd and

hexavalent Cr (Rohmann et al., 1985). Although anti-

mony was not listed, one of the primary uses of Sb is in

the manufacturing process of paints, ceramic enamels

and glasses (McGraw Hill, 1997).

Maximum concentrations of Cd, Pb, Sb and 137Cs

during the 1960s and 1970s were a factor of 2 to 4

greater in the upstream core as compared to the down-

stream core. However, the temporal trends derived

from the two cores appear to be very similar for Cd,

Pb, Sb and 137Cs. For the downstream core, the earlier

(i.e., deeper) Sb maximum is more prominent than in

the upstream core; this observation is consistent with

the high Sb concentrations observed only in 1960s

depth sections of a sediment core collected from the

Batten Kill (Table 1), one of the major tributaries that

enters the Hudson River between the two coring sites.

Maximum concentrations of Cu are ca. a factor of 2

higher in the upstream core compared to the down-

stream core during these years. In core mp 188.5, the

temporal trend of Zn differs from the other metals,

suggesting significantly different source locations,

input histories, or transport mechanisms. Between the

cores mp 188.5 and mp 163.6V, Zn concentrations at

any given time were much more similar, compared to

the large gradient observed for other metals. For a brief

interval during the early 1960s, the downstream core

had higher Zn concentrations than core mp 188.5. This

lack of concentration gradient for Zn could potentially

be explained by high Zn concentrations observed in

sediment cores collected from the Batten Kill (Table 1;

Bopp et al., 1998).

3.5. Fine-grained sediment fluxes

With improved time constraints obtained from sta-

ble Pb isotopes, we can select depth sections from these

cores that accumulated at approximately the same time.

Pairing of depth sections in time, combined with the

large Cd concentration gradient and the lack of major

downstream sources of Cd, should allow us to calculate

the relative magnitude of fine-grained sediment inputs

between the two coring locations. Such a dilution factor

is not feasible to estimate directly from measured water

column sediment fluxes since this data have not been

collected for all significant downstream sediment

inputs. Nor are metal concentrations in all the major

downstream sediment sources known. However, if we

assume that the flux-weighted average of all the down-

stream sediment sources has background levels of

metals, lower limits for the ratio of the sediment flux

past site mp 188.5 to the flux of sediments derived from

downstream sources (between mp 188.5 and mp 163.6)

can be calculated.

C188:5Fluxpast:188:5 þ CdssFluxdss

¼ C163:6VðFluxpast:188:5 þ FluxdssÞ ð1Þ

Fluxdss=Fluxpast:188:5 ¼ fðC188:5 � C163:6VÞ=ðC163:6V � CdssÞg; ð2Þ

where C188.5 = concentration of metal in site mp 188.5

core,C163.6V = concentration ofmetal in sitemp 163.6V

core, Cdss =mean weighted average concentration of


sediment sources between sites mp 188.5 and mp

163.6V, Fluxpast.188.5 = flux of sediments past site mp

188.5, Fluxdss = flux of downstream sediment sources.

This flux ratio can be expressed as a dilution factor

by Eq. (3).

Dilution Factor ¼ ðFluxdss=Fluxpast:188:5Þ þ 1 ð3Þ

In this approach, sediment cores are assumed to

provide an ‘‘ideal’’ integral sample as a function of time

in that they are representative of average suspended

particle compositions passing each location during the

time periods specified. The general agreement between

shapes of 137Cs and metal depth profiles in these cores

over a distance of 24miles along the axis of the Hudson

supports this assumption. Another implicit assumption

is that the loss of suspended sediments from riverine

transport due to net sedimentation (sedimentation–

resuspension) at any one point is insignificant com-

pared to the flux of sediments past that point. Trapping

efficiency has been modeled for the reaches of the river

between the two coring sites and ranged from 0.8% to

11% (QEA, 1999). To the degree that this latter assum-

ption may not be valid, then the minimum dilution

factors derived here represent the net effect of dilution

by downstream sediment influxes plus storage of con-

taminated sediment in upstream depositional areas.

A third assumption, that there are no other impor-

tant sources of metal contamination downstream of site

mp 188.5, is clearly not valid for most of the metals

discussed here. The flux weighted average of trace

metal concentrations in all the sources of fine-grained

sediments downstream of site mp 188.5 were probably

higher than levels measured in pre-industrial Hudson

sediments, as shown in the range of values observed in

sediments collected from the two largest tributaries

(Table 1). However, it was necessary to assume some

concentration level to be able to solve the mass

conservation equations. Consequently, the dilution

factors derived from the trace metal data are minimum

estimates since more downstream sediment would be

required by mass conservation equations if metal

concentrations in the downstream fine-particle sources

were higher than the background levels assumed.

Finally, trace metals have been assumed to be

conservative tracers of particle fluxes, i.e., that insig-

nificant amounts of metal desorption has occurred. The

majority of values of partition coefficients (Kd) for the

key metals (Cd, Pb, Sb), based on measurements in

various freshwater systems (Sarmani, 1989; Mok and

Wal, 1990; Benoit, 1995; Hurley et al., 1996; Shafer et

al., 1997; Wen et al., 1997; US EPA, 1998) are

between 104.0 and 106.5 depending on the metal and

the study. Such values are similar to the tri- and heavier

chlorinated PCBs (Bopp, 1979; Chillrud, 1996), indi-

cating that both these metals and PCBs are strongly

sorbed to particles. During periods of high runoff when

suspended solids concentrations are high, relatively

little desorption should occur for contaminants with Kd

values above ca. 104.6. However, below this Kd value,

significant desorption can occur with up to 50% of the

contaminant being in the dissolved phase during high

water transport events at a Kd of 104.0 and suspended

sediment concentrations of ca. 100 mg/l.

Between the early 1960s and the late 1970s, dilution

factors between 3 and 4 are derived from the equations

above for Cd and Sb, assuming that downstream sedi-

ment sources had metal concentrations at background

levels or levels measured in tributary sediment cores.

These dilution factors calculated from the paired

sediment cores can be compared to modeling efforts

of sediment transport. Since sediment transport in the

Hudson River is dominated by relatively few days of

high water flows and high sediment concentrations

(Bopp et al., 1985), typically during spring snowmelt,

examination of sediment dynamics during spring

highflow events should mimic the dilution observed

in these cores. A simple mass balance calculation,

using data collected in April of 1994, allows such an

alternative approach to estimating sediment dilution.

Flows along the Hudson River and its tributaries were

estimated using published USGS flows from Ft.

Edward and the Hoosic River (USGS, 1994) as well

as National Weather Service streamflow data col-

lected on the Batten Kill, with these flows scaled to

the appropriate basin size. Daily total suspended

sediment (TSS) data collected during that period

(US EPA, 1998), in conjunction with the estimated

flows, allow calculation of sediment fluxes into and

along the upper Hudson. These calculations suggest

sediment fluxes during the month of April, 1994, of

6.0� 104 metric tons of sediment at Mechanicville

(approximately 1.5 miles upstream of site mp

163.6V), and only 1.4� 104 metric tons at the

Thompson Island Dam (at site mp 188.5). Conse-

quently, 4.6� 104 metric tons of sediment were


supplied by tributaries or by in stream erosion

between these two coring locations, suggesting a

dilution factor of 4.3. Moreover, sediment modeling

efforts utilizing a mechanistic approach over a longer

time frame (March 1977 to 1992) (Quantitative Envi-

ronmental Analysis, LLC, 1999) suggest a dilution

factor of 4.0. These modeling approaches are quite

consistent with the maximum dilution factors calcu-

lated here from metal measurements made on the

paired sediment cores.

4. Conclusions

Stable lead isotopes, cadmium and antimony are

identified as sensitive tracers of upper Hudson sedi-

ments which provide additional information relevant

to both the sources of metal contamination and also

processes which affect the transport and fate of PCBs

in this river system. The large magnitude and abrupt

shifts in stable lead isotope ratios preserved in upper

Hudson sediment cores provide data to significantly

improve dating models based on radionuclide analy-

ses alone. Stable lead isotope data strongly suggests

that a hiatus in sedimentation exists in core mp

169.0A and provides independent evidence on the

timing of the hiatus. If purchasing records of Pb ore

were obtained, then stable lead isotopes could become

an even more powerful chronological tool in this

region. Cd and Sb were identified as the most sensi-

tive metal tracers of upper Hudson sediments due to

the magnitude of their contamination and the relative

Log number Depth

(cm)

137Cs

(pCi/kg)

1r 7Be

(pCi/kg)

1r

CN2215A 0–2 1290 94 2990 110

CN1852A 0–2 945 40 440 19

CN1852B 2–4 1560 62

CN1852C 4–8 3740 140

CN1852D 8–12 6250 230

lack of significant downstream sources of contamina-

tion for these metals. Metal measurements in a pair of

sediment cores located 24 miles apart on the river

were used to constrain relative fluxes of sediment

entering the river between the two coring locations,

with sediment sections deposited between the early

1960s and the late 1970s in these two cores suggesting

3–4 times more sediment entered the river between

the two coring sites than the amount of sediment

transported from upstream. These dilution factors

agree quite well with estimates based on suspended

sediment measurements during a flood event in April

1994 and with estimates based on a numerical mech-

anistic model of suspended sediment transport

between 1977 and 1992. This empirical approach

for estimating relative sediment fluxes between two

points is based on comparing metal measurements

between core sections paired as a function of time and

should be a useful independent method to test model

calculations of sediment transport. Additionally, it

provides significant constraints to the origin, transport

and ultimate fate of contaminants.

Acknowledgements

We thank the Hudson River Foundation (Hudson

007/94P) and NIEHS grants (P42 ES07384 and P30

ES09089) for support. We thank Drs. P. Santschi, F.

Marcontonio and L. Walter for useful comments

during the review process. This is LDEO contribution

number 6412. [LW]

Appendix A

Supplementary Table 1: Radionuclide and Pb isotope data for upper Hudson River cores collected near mile

point 188.5. Most lead isotope ratios made by TIMS except where noted (see footnotes below) Precision of

isotopic measurements made by quadrople ICP-MS are substantially less than other methods.

206Pb/207Pb F 2 S.E. 208Pb/206Pb F 2 S.E.

0 1.2097 0.0004 2.0321 0.0020

0 1.2436e 0.0009

1.2496 0.0004 1.9810 0.0020

1.2536 0.0004 1.9764 0.0020

1.2334 0.0004 2.0005 0.0020

1.2348e 0.001 1.9983e 0.0020

(continued on next page)

Log number Depth

(cm)

137Cs

(pCi/kg)

1r 7Be

(pCi/kg)

1r 206Pb/207Pb F 2 S.E. 208Pb/206Pb F 2 S.E.

CN1852E 12–16 6210 230 1.1841 0.0004 2.0647 0.0021

CN1852F 16–20 6230 240 1.1790 0.0004 2.0686 0.0021

CN1852G 20–24 10,500 400 1.1859 0.0004 2.0599 0.0021

1.1857e 0.001 2.0591e 0.0021

CN1852H 24–28 18,600 690 1.1716e 0.001 2.0849q 0.0208

CN1852I 28–32 6100 230 1.1364 0.0003 2.1091 0.0021

CN1852J 32–36 1020 55 1.1502 0.0003 2.1002 0.0021

CN1852K 36–40 32 6 1.1788 0.0004 2.0649 0.0021

CN1852L 40–44 7 5

CN1852M 44–47 24 5

e Denotes measurement by magnetic sector ICP-MS (ElementR).qDenotes Quadrupole measurement.

Supplementary Table 1 (continued)


Supplementary Table 2: Radionuclide and Pb isotope data for Hudson River core 169.0A. All isotopic ratios were

determined by magnetic sector ICP-MS (Element R).

Log number Depth

(cm)

137Cs

(pCi/kg)

1r 7Be

(pCi/kg)


R1075A 0–2 450 50 880 600 1.1988 0.0011 2.049 0.002

R1075B 2–4 570 70 280 920

R1075C 4–6 490 60 1.1995 0.0011 2.054 0.002

R1075D 6–8 440 60

R1075E 8–12 550 60 1.2052 0.0011 2.037 0.002

R1075F 12–16 740 70

R1075G 16–20 760 60 1.2124 0.0011 2.028 0.002

16–20 (dup) 1.2126 0.0011 2.026 0.002

R1075H 20–24 1030 90 1.2238 0.0011 2.013 0.002

R1075I 24–28 2180 120 1.2374 0.0011 1.998 0.002

24–28 1.2360 0.0011 1.997 0.002

R1075J 28–32 2110 130 1.1771 0.0011 2.072 0.002

R1075K 32–36 19 36 1.1828 0.0011 2.080 0.002

R1075L 36–40 7 32

R1075M 40–44 � 65 40

Supplementary Table 3: Radionuclide and Pb isotope data for Hudson River core 163.6V. All isotopic ratios

were determined by magnetic sector ICP-MS (Element R).

Log number Depth

(cm)

137Cs

(pCi/kg)

1r 7Be

(pCi/kg)


R1129A 0–2 320 34 530 480 1.1990 0.0008 2.059 0.003

R1129B 2–4 360 36 650 500

R1129C 4–6 470 50 3270 1240 1.1972 0.0008 2.056 0.003

R1129D 6–8 530 56 80 1370

R1129E 8–12 570 45 1.1992 0.0008 2.050 0.003

R1129F 12–16 510 54 1.2014 0.0008 2.046 0.003

R1129G 16–20 600 59 1.2113 0.0008 2.033 0.003

R1129H 20–24 780 47 1.2368 0.0009 1.999 0.003

R1129I 24–28 1070 89 1.2459 0.0009 1.987 0.003

R1129J 28–32 1510 95 1.2148 0.0009 2.025 0.003

R1129K 32–36 1930 120 1.1875 0.0008 2.062 0.003

R1129L 36–40 1810 100

R1129M 40–44 2760 160 1.1839 0.0008 2.065 0.003

Log number Depth

(cm)

137Cs

(pCi/kg)

1r 7Be

(pCi/kg)



R1129N 44–48 3620 200 1.1816 0.0008 2.067 0.003

R1129O 48–52 4940 270 1.1809 0.0008 2.067 0.003

R1129P 52–56 5600 310 1.1709 0.0008 2.078 0.003

R1129Q 56–60 4730 190 1.1364 0.0008 2.116 0.003

R1129R 60–64 2470 140 1.1417 0.0008 2.109 0.003

R1129S 64–68 1290 90 1.1457 0.0008 2.102 0.003

R1129T 68–72 890 67 1.1466 0.0008 2.103 0.003

R1129U 72–76 750 71 1.1485 0.0008 2.101 0.003

R1129V 76–80 1080 94 1.1419 0.0008 2.108 0.003

R1129W 80–84 1130 79 1.1433 0.0008 2.1095

R1129X 84–88 660 73 1.1469 0.0008 2.1086

R1129Y 88–92 510 55 1.1503 0.0008 2.1002

R1129Z 92–96 100 35 1.1673 0.0016 2.0889

R1129AA 96–100 3 27 1.1747 0.0008 2.081 0.003

R1129AB 100–104 10 32 1.1757 0.0016 2.0882

R1129AC 104–108 0 33 1.1762 0.0016 2.0923

R1129AD 108–112 � 10 44 1.1754 0.0016 2.0929

R1129AE 112–116 � 29 45 1.1713 0.0016 2.0967

R1129AF 116–119 2 45 1.1830 0.0016 2.0785


Supplementary Table 4: Trace metal data for upper Hudson River cores collected near milepoint 188. The 12–

16 cm section was extracted and analyzed twice for trace metals. Multiple analyses from a single extraction are

reported as an average value.

Log number Depth (cm) Pb (ppm) Cd (ppm) Cr (ppm) Zn (ppm) Cu (ppm) Ag (ppm) Sn (ppm) Sb (ppm)

CN2215A 0–2 142 9.4 423 44 0.2 5.9 1.7

CN1852A 0–2 278 17.1; 20.4 800 199 47 0.9 12.9 5.8

CN1852B 2–4 568 31.5 1200 270 59 7.4 10.3

CN1852C 4–8 1770 85 1310 540 129 0.4 37.8 30.0

CN1852D 8–12 2380 158 1500 680 173 2.5 20.9 39.7

CN1852E 12–16 1790; 2010 164; 166 2050 610; 670 154; 160 3.3; 2.2 13.8; 13.4 23.0; 31.7

CN1852F 16–20 1240 114 1180 580 126 2.3 12.4 24.9

CN1852G 20–24 1920 171 1420 1160 169 3.5 18.4 47.6

CN1852H 24–28 1310 86 1170 1040 109 2.5 34.3 47.2

CN1852I 28–32 790 33 2180 780 105 1.1 13.5 20.6

CN1852J 32–36 206 1.86 800 320 46 1.5 4.9 2.3

CN1852K 36–40 38 1.0 70 89 27 0.2 2.7 0.4

CN1852L 40–44

CN1852M 44–47

Supplementary Table 5: Trace metal data for Hudson River core 169.0A. The 16–20 and 24–28 cm sections

were extracted and analyzed multiple times for trace metals. Replicate analyses from a single extraction are

reported as a single average value.

Log number Depth (cm) Pb (ppm) Cd (ppm) Zn (ppm) Cu (ppm) Ag (ppm) Sn (ppm) Sb (ppm)

R1075A 0–2 53.4 1.47 164 18.3 0.24 2.38 0.87

R1075B 2–4

R1075C 4–6 56.1 1.38 205 29.1 0.33 3.47 1.10

R1075D 6–8

R1075E 8–12 75.8 3.38 241 26.5 0.30 3.62 1.34

(continued on next page)


R1075F 12–16

R1075G 16–20 161 8.05 191 41.7 0.32 6.12 3.61

16–20 (dup) 158 8.77 266 39.9 0.38 6.28 2.94

R1075H 20–24 283 17.2 320 44.7 0.70 7.25 4.10

R1075I 24–28 970 50.7 652 0.82 10.2 12.3

24–28 (dup) 934 52.2 0.71 10.6 12.6

24–28 (trip) 51.0 567 83.0 0.78 10.3 13.1

R1075J 28–32 544 37.2 560 72.3 0.58 6.96 8.89

R1075K 32–36 127 1.36 141 28.7 0.23 2.91 0.64

R1075L 36–40

R1075M 40–44



Supplementary Table 6: Trace metal data for Hudson River core 163.6V. The 96–100 cm section was extracted

and analyzed twice for trace metals. Replicate analyses from a single extraction are reported as a single average

value.


R1129A 0–2 43 0.78 114 19.9 0.32 6.45 0.80

R1129B 2–4 43 1.42 142 24.5 0.31 4.06 1.04

R1129C 4–6 55 2.32 206 31.6 0.50 4.56 1.88

R1129D 6–8 61 1.96 156 32.4 0.55 5.58 2.37

R1129E 8–12 88 3.47 198 40.5 0.81 5.01 3.56

R1129F 12–16 74 3.31 258 38.2 0.98 5.46 3.09

R1129G 16–20 110 4.78 191 35.4 0.83 5.74 2.28

R1129H 20–24 279 17.5 280 48.2 1.09 8.36 4.22

R1129I 24–28 526 25.6 405 63.7 1.77 8.45 7.73

R1129I 24–28 491 24.6 409 55.5 1.66 8.36 7.19

R1129I 24–28 533 23.1 420 59.5 1.61 8.81 7.43

R1129J 28–32 554 35.2 443 79.8 3.33 9.54 10.5

R1129K 32–36 635 42.7 434 74.9 4.77 8.80 10.1

R1129L 36–40 339 31.0 427 73.5 4.47 9.03 7.46

R1129M 40–44 635 48.9 703 99.5 4.80 12.8 14.2

R1129N 44–48 703 53.9 861 94.5 2.80 12.8 16.9

R1129O 48–52 744 64.1 878 101.8 3.03 13.5 18.9

R1129P 52–56 605 22.6 718 75.1 1.53 13.5 26.2

R1129Q 56–60 611 21.2 579 83.8 1.74 13.6 19.3

R1129R 60–64 342 13.7 574 68.2 1.13 8.28 9.80

R1129S 64–68 306 11.0 900 72.2 0.99 8.99 7.41

R1129T 68–72 189 6.57 591 98.4 1.14 9.08 4.54

R1129U 72–76 156 4.32 366 56.4 0.69 7.70 2.85

R1129V 76–80 356 8.63 832 93.0 1.27 10.71 3.19

R1129W 80–84 279 500 93.8

R1129X 84–88 215 17.1 312 66.9

R1129Y 88–92 215 358 71.6

R1129Z 92–96 191 368 60.6

R1129AA 96–100 164 0.96 318 43.5 0.38 5.00 1.17

96–100 (dup) 0.87 0.41 4.62 0.97

R1129AB 100–104 155 330 55.1

R1129AC 104–108 134 263 49.0

R1129AD 108–112 187 233 50.5

R1129AE 112–116 213 214 57.9

R1129AF 116–119 215 174 60.5


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