FINAL REPORT
Deep Leaching of Pesticides and Nitrate
at USDA Forest Service Tree Seedling Nurseries
by
Kenneth P. BentsonEnvironmental Science
New Mexico Highlands UniversityLas Vegas, NM 87701
and
Terry L. LavyUniversity of ArkansasAltheimer Laboratory
Fayetteville, AK
recd 06/1?
1
INTRODUCTION
Pesticides and fertilizers have been identified as
pollutants of groundwater. Forestry practices usually do not
contaminate groundwater, because pesticide and fertilizer use is
less intensive than in other cropping systems. The forestry
operation most likely to contaminate groundwater is bare-root
tree seedling production.
Fertilizers, insecticides, herbicides and fungicides are
used intensively at tree seedling nurseries, because of the high
crop value. Irrigation and tillage of nurseries is a common
practice. Most USDA Forest Service tree seedling nurseries are
in areas with poorly characterized hydrogeology. Few studies of
the environmental fate of pesticides and fertilizers in tree
seedling nursery soils have been undertaken.
This study was designed to monitor the vadose zone for the
presence of nitrate and 6 commonly applied pesticides with high
leaching potential. Lysimeters installed for this study are
available for use by other investigators.
The objectives of this study were:
1. Measure the concentrations of agricultural chemicals
(e.g., Diazinon (0,0 diethyl ester of 0-[6-methy1-2-(1-
methylethyl)-4-pyrimidinyl-phosphorothioic acid [ACS
Reg. No. 333-41-5]), Chlorothalonil (2,4,5,6-
tetrachloro-1,3-benzenedicarbonitrile [ACS Reg. No.
1897-45-6]), DCPA (dimethyl ester of 2,3,5,6-
tetrachloro-1,4-benzenedicarboxylic acid [ACS Reg. No.
2
1861-32-1], Captan (N-(trichloromethylthio)-1,2,3,6-
tetrahydrothalimide [ACS Reg. No. 133-06-2]),
Diphenamid (N,N-dimethyl-a-phenyl-benzeneacetamide
[ACS Reg. No. 957-51-7]), Benomyl (Methyl ester of [1-
(butylamino)-carbonyl]-1H-benzimidazol-2-yl-carbamic
acid [ACS Reg. No. 17804-35-2]), and nitrate (NO:))
that have a history of intensive use in tree seedling
nurseries in vadose zone water under bare-root tree
seedling beds.
Determine seasonal fluctuations in pesticide and nitrate
concentrations in vadose zone water under bare-root
tree seedling beds.
Establish a permanent sample collection system to
monitor deep leaching of potential groundwater
contaminants at forest nurseries.
4. Provide information suitable for risk assessments of
contamination of aquifers by agricultural chemicals
from nurseries.
Benomyl is a fungicide that is used in 5 of the 11
nurseries. Benomyl is to be investigated in this study because
of its intensive use, and its potential as a mutagen or
carcinogen (EPA, 1985; EPA, 1986). Some leaching of this
compound is expected.
The fungicide captan was selected since it is used in 4 of
the 11 nurseries and is mutagenic, carcinogenic, and immunotoxic
(Klaasen et. al., 1986).
3
Chlorothalonil is a fungicide that has shown evidence of
mutagenesis and carcinogenesis (EPA, 1984). Chlorothalonil is
used at 4 of the 11 nurseries. This compound has been
investigated in the EPA's national drinking water study.
The herbicide DCPA, or dacthal, has a high leaching
potential. This was listed as a high priority compound in the
EPA's drinkiing water survey.
Diazinon is an organophosphorus insecticide. Diazinon was
selected because of its relatively high acute toxicity (acute
oral LDs„, in rats of 250 mg/kg (Gaines, 1969)) and its use at 4
of the 11 nurseries. Diazinon was included in the EPA's drinking
water survey.
Diphenamide is an herbicide that has a history of use with
the last 6 years at 5 of the nurseries. This compound has the
highest leaching potential of all pesticides to be studied, and a
relatively long half-life of 135 days.
Nitrate is a common contaminant of groundwater (Thompson and
McQuillan, 1984; Hubbard and Gascho, 1986; Yusop and Cleemput,
1984; and Spalding and Exner, 1982). Nitrate from fertilizer
applications and livestock feedlots has contaminated many wells
and aquifers across the United States. The U.S. Environmental
Protection Agency has set a Maximum Contaminant Level of 10 mg/L
nitrate in potable water supplies (Federal Register 1975),
because of the occurence of methemoglobinemia (blue baby
syndrome) in babies that ingest nitrate in water.
Several other pesticides have been used extensively in the
4
nurseries, but were not selected for this study. Bifenox
(Methyl-5-(2',4'-dichlorophenoxy)-2-nitrobenzoate) has been used
in 7 nurseries, however, it was not selected because of (1) low
acute toxicity, (2) no evidence of matagenesis or carcinogenesis,
(3) relatively short soil half-life, and (4) low leaching
potential. Six of the nurseries have used the herbicide
oxyfluorfen (2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-
(trifluoromethyl)benzene), which was not selected because (1) low
leaching potential, (2) 35 d half-life, and (3) low toxicity.
Glyphosate herbicide (N-phosphonomethylglycine) has been
historically used at 5 of the nurseries, however, it was not
selected because it adsorbs tightly to soils and has a very low
mammalian toxicity. The soil fumigants, methyl bromide and
chloropicrin were not selected because of their low aqueous
solubilities and high volatilities which preclude leaching.
MATERIALS AND METHODS
Lysimeter Site Selection
Lysimeters were installed at USDA Forest Service bare-root
tree seedling nurseries across the U.S. (Ashe Nursery,
Mississippi; Bend Pine Nursery, Oregon; Bessey Nursery, Nebraska;
Couer d'Alene Nursery, Idaho; Humboldt Nursery, California; Lucky
Peak Nursery, Idaho; Placerville Nursery, California; Stone
Nursery, Oregon; Tuomey Nursery, Michigan; Wind River Nursery,
Washington). Lysimeters were installed vertically at the edge of
bare-root beds to depths of approximately 3 m, where practical
(Table 1). Target locations for lysimeters were low spots in the
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Table 1. Locations and depths of lysimeters.
Lysimeter Location and DepthAshe Nursery, Mississippi
A021 SE Corner Block 2, 3 m depthA012 NE Corner Block 1, 3 m depthA113 W Edge Block 11, 3 m depthA144 SW Corner Block 14, 3 m depth
Bend Pine Nursery, OregonBP15B1 SE Corner Block 15, 1 m depth to rockBP182 SW Corner Block 18, 1 m depth to rockBP15A3 Near NW Corner Block 15, 1 m depth to rockBP104 S edge Block 10 near sprinkler riser 3, 1 m depth
to rock
Bessey Nursery, NebraskaN071 Corner Block 7, 2.4 m depthN092 Edge Block 9, 2 m depthN013 Edge Block 1, 3 m depthNA4 Edge Block A, 3 m depth
Coeur d'Alene Nursery, IdahoC51 Edge of Block 5, 2.1 m depthC62 S Edge of Block 6, 2.4 m depthCG3 By Container Seedling Greenhouse, 2.7 m depthC74 Edge of Block 7, 2.1 m depthC65 N edge of Block 6, 1.8 m depthCG6 Drain spot between greenhouses, 3 m depth
Humboldt Tree Nursery, CaliforniaHAl NW Corner Block A, 3 m depthHI3 Center S Edge Block I, 3 m depthHJ2 N Corner, S of road and W of sump Block J, 3 m
depthHL4 3 m W of drain on mid-S edge Block L, 3 m depth
Lucky Peak Nursery, IdahoL111 Near NE Corner Block 11, 3 m depthL132 Center E Edge Block 13, 3 m depth on rockL083 SE Corner Block 8, 3 m depth on rockL044 Center E Edge Block 4, 3 m depth
Placerville Nursery, CaliforniaPS1 SW Corner Block S-3, 3 m depthPJ2 Across road from SE Corner Block J-1, 3 m depthPM3 W edge Block M-3, 3 m depthPM4 S edge Block M-2, 3 m depth
6
Table 1. Continued
Lysimeter Location and Depth
Stone Nursery, OregonSC1 W edge Block C, near sprinkler riser 32, 3 m depthSF2 W edge Block F, near sprinkler riser 26, 3 m depthSD3 W edge Block D, near sprinkler riser 32, 3 m depthSC4 E edge Block C, 3 m depth
Tuomey Nursery, MichiganTE1 E edge Block E, 2.4 m depthTG2 Near Implement Shed Block G, 2.6 m depthTB3 Corner Block B, 2.4 m depthTA4 A Block edge near houses, 2.7 m depth
Wind River Nursery, WashingtonW61 SW Corner Block 6, 2.4 m depth on rockWT2 NE Corner Block TCS, 3 m depthWB3 SE Corner Block BHN, 3 m depthWN4 S Corner Block 35, 1.5 m in cobbles/boulders
7
nursery, downslope locations from large sets of blocks, known
water drainage areas, or where managers had particular concerns.
Placement of lysimeters was limited by underground irrigation
pipes, agricultural equipment clearances, and other management
practices.
Lysimeter Installation
Teflon pressure-vacuum lysimeters (Timco Mfg., Inc.) were
cleaned by rinsing three times each with pesticide grade 1-
propanol, acetone, and laboratory deionized water. Lysimeters
were reassembled in the laboratory and tested for air leaks.
Leaks were sealed with teflon tape and the lysimeters wrapped in
clean aluminum foil and packaged in plastic bags. Teflon tubes
and stopcocks were cleaned with 3 rinses each of acetone and
deionized water.
Lysimeters were installed into vertical boreholes drilled
with 15-cm diameter hollow auger drill bits (where available).
Prior to drilling, a 1.5 m diameter circle was hand dug to about
0.4 m, to remove contaminated surface soil that might fall into
the borehole during drilling. Surface soil was kept separate
from drill cast.
Lysimeters were attached to 5-cm diameter PVC well-casings
cut to the appropriate length for the borehole. Vacuum-pressure
and sample recovery tubes went through the well casings, and the
surface ends of casings were sealed with 2-hole corks through
which the tubes passed. Lysimeters were centered in boreholes
with centering devices. Silica slurry (Timco Mfg., Inc.) was
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prepared with distilled water. Sufficient slurry was introduced
into boreholes to cover the lysimeters completely. Lysimeters
were lowered into boreholes until they were immersed in the
silica slurry. The slurry was allowed to set for 1 h.
Sufficient bentonite was poured into boreholes to provide a 10-cm
cap over the silica slurry. Boreholes were backfilled with drill
cast and tamped. At 0.6 m, another 10-cm layer of bentonite was
placed in boreholes. Bentonite seals prevented surface water
from migrating down the disturbed borehole soil to the
lysimeters.
Surface housings for lysimeters were constructed by placing
a 1-m lengths of 15-cm diameter PVC pipe in boreholes and tamped
into position, with about 30 cm above the soil surface. PVC pipe
housings contained the top of well casings and lysimeter's
vacuum-pressure and sample recovery tubes. PVC caps were placed
on the 15-cm PVC pipes.
The ends of lysimeter tubes were sealed with aluminum foil
and plastic bags during installation, to prevent contamination of
the access tubes and lysimeters. The sample collection tube was
terminated at the surface with a teflon stopcock. The vacuum-
pressure tube was terminated with a stopcock attached to a
vacuum-pressure gauge and a vacuum pump connection at the
surface. The vacuum-pressure gauge, however, tended to rapidly
corrode under field conditions and thus leak air.
The assemblies were modified at the Stone Nursery, and have
been found to perform adequately. The modification consists of
9
having a single vacuum-pressure gauge end that can be carried to
each lysimeter at a nursery. The lysimeter's vacuum-pressure
line is terminated with a teflon stopcock.
Sample Collection
Samples were collected by nursery personnel in December,
April, June, and September in 1989, 1990, and 1991. Nursery
personnel were instructed in sample collection during lysimeter
installation. A standard operating procedure for sample
collection and shipment was also provided each nursery.
The collection procedure consisted of the following:
Four 1000-mL Teflon bottles were shipped by the Forestry
Sciences Laboratory, Corvallis, Oregon to each nursery
in an ice chest.
Upon receipt of the sample bottles, the nursery employee
responsible for sample collection placed a vacuum on
the lysimeter. The vacuum was maintained for one week.
3. Sample recovery from lysimeters:
The sample collection tube tip at the stopcock, a 1
L Erlenmeyer flask, and a graduted cylinder were rinsed
with pesticide grade acetone to remove contaminants.
The sample collection tube tip was inserted in a
tube in a rubber stopper on the Erlenmeyer flask.
c) The vacuum-pressure and sample collection stopcocks
were opened. A vacuum was applied to the erlenmeyer
flask side-arm and the lysimeter contents were drawn to
the surface. The vacuum was maintained until no
10
further water was withdrawn from the lysimeter. [NOTE:
at no time was pressure applied to the lysimeter,
pressurizing the lysimeter destroys the seal between
the silica packing and the lysimeter cup.
d) Stopcocks were closed.
The volume of sample water was measured with the
graduated cylinder and placed in the Teflon sample
bottle. A chain of custody document was filled in by
the employee, and signed.
Sample bottles were frozen, and returned to the
laboratory packed in dry ice.
Chemical Analyses
Nitrate Analysis
Nitrate concentration was determined by cadmium reduction
and colorimetric detection with an autoanalyzer (Technicon
Industrial Method #100-70 W). This method requires a minimum of
analyst involvement. The detection limit for nitrate by this
method is 1 ppb. Samples with greater than 100 ppb were diluted
to bring them into the linear range of the standard calibration
curve. Nitrate analysis was performed at the USDA Forest
Service Forestry Sciences Laboratory by the Cooperative Chemical
Analytical Laboratory (COAL) in Corvallis, Oregon.
Pesticide Analyses
The pesticides investigated in this study were benomyl,
captan, chiorothalonil, dacthal, diazinon, and diphenamid. Theanalytical methods used were those of Pressley and Longbottom
11
(1982b), Sherma and Stellmacher (1985), Marti et al. (1984),
Hargesheimer (1984), Pressley and Longbottom (1982a), and
Kacvinsky et al. (1983) for benomyl, captan, chlorothalonil,
dacthal, diazinon, and diphenamid, respectively. Pesticide
residue analyses were performed at the Altheimer Laboratory of
the University of Arkansas.
RESULTS AND DISCUSSION
Nitrate
All nurseries showed some level of nitrate contamination of
soil water (Table 2). The Bessey, Coeur d'Alene, Lucky Peak,
Stone, Tuomey, and Wind River nurseries had soil water
concentrations in excess of the EPA Maximum Contaminant Level for
nitrate in drinking water (10 mg/L). The Ashe, Bend Pine, and
Humboldt nurseries may have similar situations, however, there
were few samples from each of these nurseries and no conclusion
can be drawn.
Fertilization for seedling production appears to result in
variable concentrations of nitrate in soil water. The
variability may be the result of interactions between
precipitation, soil disturbance, soil texture, and fertilization.
For instance, at the Lucky Peak and Stone Nurseries, both occur
in areas with clayey soils that lack sand. Nitrate
concentrations are higher at Lucky Peak than at Stone, but Lucky
Peak is in a drier environment. Less precipitation (Lucky Peak)
will carry nitrate less deeply into a soil, than in an area with
high precipitation (Stone). Nitrate concentrations in soils may
Table 2. Nitrate concentrations observed in soil water.
Nursery Lysimeter Date Lab # mg/L NO,
Ashe Nursery, MississippiA012 1/20/92 267 1.98
Bend Pine Nursery, OregonBP1822 turbid 11/8/90 156 0.14
Bessey Nursery, NebraskaNA41 6/22/90 130 16.06N0131 6/22/90 131 39.15N0711 6/22/90 132 26.86N0921 6/22/90 133 0.14N0712 11/8/90 152 46.40N0922 11/8/90 153 0.15N0132 11/8/90 154 47.16NA42 11/8/90 155 18.60
Coeur d'Alene Nursery, IdahoCcomb. 11/89 107 7.95C511 6/11/90 116 11.02C621 6/11/90 117 4.20C651 6/11/90 118 3.88C741 6/11/90 119 7.55CG61 6/11/90 121 1.96C512 11/8/90 138 11.52C652 11/8/90 140 1.36C742 11/8/90 141 4.83CG62 partic. spl 11/8/90 143 1.45C517 11/5/91 244 2.10C657 11/5/91 246 0.05C747 11/5/91 247 0.06CG37 11/5/91 248 0.03CG67 11/5/91 249 <0.01C518 2/14/92 278 2.39C658 2/14/92 280 <0.01C748 2/14/92 281 0.07CG68 2/14/92 283 0.53
Humboldt Nursery, CaliforniaHC 4/17/90 111 3.72
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Table 2. Nitrate concentrations observed in soil water.
Nursery Lysimeter Date Lab # mg/L NO,
Lucky Peak Nursery, IdahoLcomb. 11/89 106 21.48L0441 6/11/90 122 23.71L0831 6/11/90 123 44.44L1111 6/11/90 124 14.17L1321 trace h2o 6/11/90 125 178.67L0832 11/8/90 145 44.96L1112 11/8/90 146 16.75L1322 11/8/90 147 199.33L0837 11/15/91 255 52.82L1327 11/15/91 257 215.81L083 3/25/92 293 27.01L111 3/25/92 294 54.20L132 3/25/92 295 222.02
Placerville Nursery, CaliforniaPC 11/89 105 8.33PJ21 11/8/90 134 4.69
Stone Nursery, OregonScomb. 11/89 104 32.80SC12 11/8/90 160 40.76SC42 11/8/90 161 33.90SD32 11/8/90 162 22.33SF22 11/8/90 163 23.78SC1 12/18/91 262 41.35SC4 12/18/91 263 28.43SD3 12/18/91 264 25.12SF2 12/18/91 265 3.65SC1 1/22/92 274 163.99SC4 1/22/92 275 26.54SD3 1/22/92 276 16.61SF2 1/22/92 277 10.55
Tuomey Nursery, MichiganTEll 5/25/90 112 10.85TB31 5/25/90 113 20.66TA42 11/8/90 148 2.72TB32 11/8/90 149 14.30TE12 11/8/90 150 41.87TE17 11/25/91 260 39.25
13
Table 2. Nitrate concentrations observed in soil water.
Nursery Lysimeter Date Lab # mg/L NO,
Wind River Nursery, WashingtonWB31 6/11/90 126 5.19WG11 6/11/90 127 0.02WN41 6/11/90 128 0.00WT21 6/11/90 129 12.91W1189 12/13/89 103 5.02W612 11/8/90 164 0.03WB32 11/8/90 165 5.38WN42 11/8/90 166 0.13WT22 11/8/90 167 11.14W617 11/5/91 250 0.03WB37 11/5/91 251 5.52WN47 11/5/91 252 0.36WT27 11/5/91 253 9.83W618 2/14/92 284 0.97WB38 2/14/92 285 5.22WN48 2/14/92 286 0.34WT28 2/14/92 287 10.71
14
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be lower at nurseries with sandy soils, because the nitrate was
washed through the lysimeter depth to deeper horizons prior to
sampling.
Management practices should be changed to reduce the use of
nitrogen fertilizers at seedling nurseries. The high
concentrations at several nurseries, and results from other
studies, suggest this is a critical problem at all of the
nurseries. Options for protection of potable groundwater
supplies should be investigated at each nursery.
Pesticides
The pesticides detected in soil water were chlorothalonil,
DCPA, and benomyl (Table 3). The frequency of pesticide
detection was low, suggesting that pesticides do not typically
reach the lysimeter depth in soil water. Benomyl was found at
the Stone and Wind River nurseries at the greatest concentrations
observed of any pesticide (0.14 - 0.84 µg/L). The Wind River
and Stone nurseries are in a climatological region characterized
by plentiful precipitation that arrives during the winter.
Apparently, certain lysimeters were more likely to capture
pesticide residues (lysimeters WN4 and W61 at Wind River,
lysimeter CG6 at Coeur d'Alene, and lysimeter NA4 at Bessey),
whether these results correlate with a pesticide application(s)
is uncertain. Apparently, pesticide migration into deeper soil
strata is a sporadic, low-level, occurence at certain locations
within nurseries.
Chlorothalonil and benomyl are suspect carcinogens. The
16
Table 3. Pesticides detected at the nurseries. Pesticide codes:1, Diazinon; 2, Chlorothalonil; 3, DCPA; 4, Captan; 5,Diphenamid; and 6, Benomyl. Concentrations are in iLg/L.
PESTICIDE1 2 3 4 5 6
Ashe Nursery, MississippiA012-5-91 nd nd nd nd nd ndA144-5-91 nd nd nd nd nd nd
Bend Pine Nursery, Oregon12-89 nd nd nd nd nd nd
Bessey Nursery, NebraskaNA41-6-90 nd nd 0.01 nd nd ndN0131-6-90 nd nd nd nd nd ndN0711-6-90 nd nd nd nd nd ndN0921-6-90 nd nd nd nd nd ndNA4-2-11-90 nd nd nd nd nd ndN071-2-11-90 nd nd nd nd nd ndN092-2-11-90 nd nd nd nd nd ndN013-2-11-90 nd nd nd nd nd ndNA4-6-90 nd nd 0.01 nd nd ndN013-6-90 nd nd nd nd nd ndN071-6-90 nd nd nd nd nd ndN092-6-90 nd nd nd nd nd ndN092-9-902 nd nd nd nd nd ndNA4-9-90 nd nd nd nd nd ndN013-9-90 nd nd nd nd nd ndN071-9-90 nd nd nd nd nd ndN071-5-91 nd nd nd nd nd ndN092-5-91 nd nd nd nd nd ndN013-5-91 nd nd nd nd nd ndNA4-5-91 nd nd nd nd nd nd
Couer d'Alene Nursery, IdahoCA11-89 nd nd nd nd nd ndCA1-90 nd nd nd nd nd ndCG6-10-90 nd 0.02 nd nd nd ndC51-10-90 nd nd nd nd nd ndC51-5-91 nd nd nd nd nd ndC65-5-91 nd nd nd nd nd ndCG6-5-91 nd nd nd nd nd ndC-10-90 nd nd nd nd nd ndC65-9-90 nd nd nd nd nd ndC74-9-90 nd nd nd nd nd ndCG6-9-90 nd 0.02 nd nd nd ndC51-9-90 nd nd nd nd nd nd
Table 3. Continued. Pesticide codes: 1, Diazinon; 2,Chiorothalonil; 3, DCPA; 4, Captan; 5, Diphenamid; and 6,Benomyl. Concentrations in ppb.
1 2 3 4 5 6
Humboldt Nursery, CaliforniaHB4-17-90 nd nd nd nd nd ndHB1-90 nd nd nd nd nd ndH-10-90 nd nd nd nd nd nd
Lucky Peak Nursery, IdahoLP3-20-90 nd nd nd nd nd ndLP12-89 nd nd nd nd nd ndL083-10-90 nd 0.02 nd nd nd ndL-10-90 nd 0.01 nd nd nd ndL132-9-90 nd nd nd nd nd ndL083-9-90 nd nd nd nd nd nd
Placerville Nursery, CaliforniaPV11-89 nd nd nd nd nd ndPV12-89 nd nd nd nd nd nd
Stone Nursery, OregonST11-89 nd nd nd nd nd ndSC1-6-91 nd nd nd nd nd ndSC4-6-91 nd nd nd nd 1 ndSD3-6-91 nd nd nd nd nd ndSF2-6-91 nd nd nd nd nd ndS-10-90 nd nd nd nd nd ndSF2-9-90 nd nd nd nd nd 0.84SC4-9-90 nd nd nd nd nd ndSC1-9-90 nd nd nd nd nd ndSD3-9-90 nd nd nd nd nd nd
Tuomey Nursery, MichiganTEll nd nd nd nd nd ndTE1-2 nd nd nd nd nd ndTE1-5-90 nd nd nd nd nd ndTE1-9-90 nd nd nd nd nd ndTE1-5-91 nd nd nd nd nd nd
17
18
Table 3. Continued. Pesticide codes: 1, Diazinon; 2,Chlorothalonil; 3, DCPA; 4, Captan; 5, Diphenamid; and 6,Benomyl. Concentrations in ppb.
1 2 3 4 5 6
Wind River Nursery,WR11-89
Washingtonnd nd nd nd nd nd
WR12-89 nd nd nd nd nd ndWT2-10-90 nd nd nd nd nd ndW61-10-90 nd nd nd nd nd 0.14WN4-10-90 nd 0.01 nd nd nd ndWB3-10-90 nd nd nd nd nd ndW61-9-90 nd nd nd nd nd ndW61-5-91 nd nd nd nd nd 0.16WB3-5-91 nd nd nd nd nd ndWN4-5-91 nd nd nd nd nd 0.34WT2-5-91 nd nd nd nd nd ndW-10-90 nd nd nd nd nd ndWT2-9-90 nd nd nd nd nd ndWB3-9-90 nd nd nd nd nd ndWN4-9-90 nd nd nd nd nd nd
19
Forest Service should consider restricting the use of these
pesticides at most nurseries, because of potential contamination
of potable groundwater supplies. It is strongly recommended that
the use of benomyl in the Pacific Northwest be discontinued,
unless potable groundwater supplies are distant from the nursery
and groundwater does not move toward domestic wells.
CONCLUSION
Lysimeters at approximately 3 m depths at Forest Service
nurseries showed that nitrate migration through the vadose zone
is substantial at most nurseries. Intensive nitrogen
fertilization regimes have resulted in toxicologically
significant concentrations of nitrate in soil water at some
nurseries. The consequences of adverse impacts to potable
groundwater supplies from nitrate leaching should be investigated
at all nurseries.
Pesticide leaching appears to be negligible. Chiorothalonil
and benomyl leaching is evident at several nurseries. Benomyl,
in particular, appears to leach to a greater extent than other
pesticides in the Pacific Northwest.
It is recommended that (1) a monitoring well be installed
into potable water aquifers in the center of nurseries close to
deomestic wells, (2) groundwater flow directions and volumes
beneath the nurseries should be investigated, (3) the use of
chlorothalonil and benomyl be restricted at some nurseries, and
(4) alternative nitrogen fertilizer regimes should be tested for
use at the nurseries.
20
LITERATURE CITED
EPA Chlorothalonil Registration Standard; U.S. EnvironmentalProtection Agency, Office of Pesticides and ToxicSubstances: Washington, D.C., 1984; Toxicological Chapter.
EPA Toxicological Review Studies Using Benomyl; U.S.Environmental Protection Agency, Office of Pesticides andToxic Substances: Washington, D.C., 1985.
EPA EPA Tox. One-liner for Benomyl; U.S. Environmental ProtectionAgency, Office of Pesticides and Toxic Substances:Washington, D.C., 1986; Tox. Chem No. 75A.
Gaines, T.B. Toxicol. Appl. Pharm., 1969, 14, 515.
Hargesheimer, E.E. J. Assoc. Off. Anal. Chem., 1984, 67, 1067.
Hubbard, R.K.; Gascho, G.J. Trans. of the ASAE, 1986, 29, 1564.
Kacvinsky, J.R., Jr.; Saito, K.; Fritz, J.S. Anal. Chem., 1983,55, 1210.
Klaasen, C.D.; Amdur, M.O.; Doull, J. Cassarett and Doul1'sToxicology, Third Ed.; MacMillan Publ. Co.: New York, 1986,pp561.
Marti, L.R.; DeKavel, J.; Dougherty, R.C. Environ. Sci. Technol.,1984, 18, 973.
Pressley, T.A.; Longbottom, J.E. The Determination ofOrganophosphorus Pesticides in Industrial and MunicipalWastewater: Method 622 (EPA-600/4-82-008); U.S.Environmental Protection Agency: Washington, D.C., 1982a;pp25.
Pressley, T.A.; Longbottom, J.E. The Determination of Benomyl andCarbendazim in Industrial and Municipal Wastewater: Method631 (EPA 600/4-82-012); U.S. Environmental ProtectionAgency: Washington, D.C., 1982b; pp19.
Sherma, J.; Stellmacher, S. J. Liq. Chromatogr., 1985, 8, 2949.
Spalding, R.F.; Exner, M.E. J. Hydrolog., 1982, 58, 307.
Thompson, G.M.; McQuillan, D.M. Nitrate Contamination ofGroundwater in Albuquerque (No. 7); New Mexico Bureau ofMines and Mineral Resources: New Mexico, 1984; pg 204-216.
Yusop, M.K.; Cleemput, 0. Environ. Pollut. B, 1984, 7, 43.