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

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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

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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

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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

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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

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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

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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.

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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.