00064-8 Environmental Fate of Synthetic Pyrethroids

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ENVIRONMENTAL FATE OF SYNTHETIC PYRETHROIDS DURING SPRAY

DRIFT AND FIELD RUNOFF TREATMENTS IN AQUATIC MICROCOSMS

Karen M. Erstfeld

Department of Environmental Sciences, Rutgers University

14 College Farm Road, New Brunswick, NJ 08903

Phone (732) 932-9817, FAX (732) 932-8644

(E-mail: Kerstfeld@~aol.com)

(Received in USA 24 June 1998; accepted 21 January 1999)

Received Date:

ABSTRACT The aquatic fate and persistence of synthetic pyrethroids under spray drift and field runoff treatment regimes were determined in outdoor pond microcosms. In this paper, the experimental design and construction of outdoor microcosms is presented, as well as the aquatic fate oftralomethrin and deltamethrin. Tralomethrin is rapidly degraded to deltamethrin, with a half-life of 12.7 hours under spray dritt conditions. Degradation profiles of tralomethrin in water indicated rapid conversion of deltamethrin and to less active isomers and then to decamethrinic acid (BR2CA). After 24 hours, the percent radioactivity of tralomethrin was 25% of the test material in the water column. In sediment, tralomethrin was immediately converted to deltamethrin. © 1999 Elsevier Science Ltd. All rights reserved

1737 1738

Deitamethrin is rapidly degraded with a half-life of 8 to 48 hours, depending on mechanism of introduction into water. Degradation profiles of deltamethrin in water indicated rapid conversion of deltamethrin to decamethrinic acid (BR2CA), comprising approximately 90% of the radioactivity in the aqueous phase at 168 hours. Extraction and analysis of fathead minnows (Pimephales promelax) after 96 hours revealed that tissue residues contained parent compounds and metabolites ct-R-deltamethrin, trans-deltamethrin and Br2CA. Fish residues are directly related to aqueous concentrations, thus bioavailability under field runoff regimes were an order of magnitude lower than tissue residues under spray drift conditions. Plant tissue was found to significantly accumulate pyrethroids.

Key Words: aquatic fate, microcosms, spray drift, field runoff, deltamethrin, tralomethrin, pyrethroids

Introdoction Although most investigations of environmental fate are laboratory-based, outdoor pond microcosms and mesocosms have been used in recent years in ecological risk assessment of pesticides, providing integrated information beyond individual laboratory studies [1-7]. Microcosms can allow for the monitoring of residue concentrations of parent and degradation products in sediment, water, plants and in organisms as a function of time and can provide detailed exposure information, not only for parent compound, but also for degradation products, as well. Results from this investigation are intended to aid the interpretation of ecological fate data that has been collected from individual laboratory investigations, in order to provide more realistic fate and exposure information for a comprehensive ecological risk assessment for tralomethrin and deltamethtin. Tralomethrin, is the active ingredient of Scout 0.3 EC and Scout Xtra 0.9 EC. Deltamethrin, is the active ingredient of Decis 2.5 EC. Both compounds are synthetic pyrethroid insecticides for use on cotton. The toxicity of synthetic pyrethroids to aquatic organisms has in established in laboratory studies and are typically in the low ppb range for fish [l]. Few studies have been performed to evaluate the dynamics of pyrethroid degradation in aquatic ecosystems. Previous studies have reported the degradation of the synthetic pyrethroid deltamethtin in ponds to be rapid, with half-lives less than 24 hours [2,3]. 1739

A series of pond outdoor microcosms were designed and constructed to determine the fate and persistence of tralomethrin and deltamethrin, two synthetic pyrethroid insecticides, under spray drift and field runoff treatment regimes. The objectives were to i) determine the fate and persistence of tralomethrin and deltamethrin in a simulated outdoor pond environment. ii) determine their relative distribution in water, sediment, macrophytes, and fish; iii) compare their aquatic fate under simulated spray drift and field runoff treatment regimes, and iv) determine the major degradation products in an aquatic environment. The chemical structures of tralomethrin, deltamethrin and its degradation products are shown in Figure 1.

Materials and Methods Test Materials

Radiolabeled 14C (methyl labeled) Tralomethrin (RU 25474, [1-R-[la(S*),3c~]]- 2,2,dimethyl-3 -(1,2,2,2 -tetrabromoethyl)-cyclopropane carboxylic acid, cyano (3- phenoxyphenyl)methyl ester, CAS # 66841-25-6, a solution in toluene, was received from Roussel Uclaf, Paris, France. This material had a specific activity of 60 mCi/mmole and a radiopurity of 97.7%. Traiomethrin has a molecular weight of 667.03 mg/mmole. Radiolabeled 14C (methyl labeled) Deltamethrin (RU22974, [1R-[1-R-[la(S*),3et]]-3-(2,2,dibromoethenyl)- 2,2dimethylcyclopropanecarboxylic acid, cyano(3-phenoxyphenyl)methyl ester, CAS#52918-63- 5), had a specific activity of 60 mCi/mmole and a radiopurity of 100%. Deltamethrin has a molecular weight of 505.22 mg/mmole. Test materials were stored in a freezer maintained at approximately -80 °C in the dark. The structures of Tralomethrin and Deltamethrin, including the position of the radiolabel, and its degradation products are shown in Figure 1. The degradation products include ~tR-Deltamethrin, trans-Deltamethrin and Decamethrinic acid (Br2CA).

Microcosm Destgn and Construction A series of three microcosms (one series for tralomethrin, the other series of three for deltamethrin) were constructed of fiberglass - one microcosm each to simulate spray drift, field runoff and control treatment regimes. These cylinders, each 1.2 m in diameter and 1.2 m tall, were placed on end in two 3 m diameter by 1.2 tall fiberglass cylinders (three smaller tanks 1740

-- -* * O CN

Br ~ ~!~ :i~,~,i,,'~0,,,,,'~~0 ~/ • ~

tralomethrin ~,~ ,,%c,,.~* * n ....~,~~o,~CN ~/c=~'%..J~....."~o.."~L~ ~L~

deltametbri~

* * O CN H3C .CH: '1 I _ _

Br'~c_~c/ Br / tr~-d¢Ita~etkd~

..* *.,.. o CN l~r~Br/C'-=-C',,,,,,,,~,,....'C.o~**'C~O~ H~_ .~.r~ II I _

=-R-deltamethrin

s~ .,~ .~.. ,o, Br/C = C,,,,,,,,,~ ..,....."C~.OH

Br~CA * - Denotes radiolabel location Figure ]. Chemical structures oftralomcthrJn, de]tamcthfin and degradation products, 1741 within one larger), resting on a level bed of sand. The water level was maintained between 0.85 and 0.95 m (990 - 1100 liters) throughout the investigation. Approximately a 6cm layer of sediment was placed in aluminum trays (14 cm wide by 29.8 cm long by 8.3 cm deep, 150 Kg total mass of sediment). Shoots of the narrow leaf pond weed (Potamogeton sp.) were inserted into the sediment trays. Once the sediment trays and plants were in place, water was slowly pumped into each microcosm vessel, with the initial water depth was approximately 1050 liters. In addition, 21 petri dishes of sediment (10 cm by 1.5 cm deep, with 1.0 cm sediment, 2100 g total mass of sediment) were deployed on the bottom of each microcosm approximately 3 weeks prior to treatment. The number and size of the sediment trays and Petri dishes were selected in order to simulate the same ratio of water to sediment surface area typical for natural ponds. Prior to construction, the microcosm tanks were washed with a mild detergent and rinsed with water. The large tanks were filled with water and used as water baths, designed to maintain water temperatures between 19 and 24 °C. In order to maintain water temperature, a chiller unit was used and circulated water at approximately 1.8 gallons/minute. This flow rate circulated all water in the water baths approximately 1.5 times every 24 hours. The water baths were wrapped in insulation to minimize heat loss due to radiative cooling.

Microcosm Preparation and Acclimation Preparation of the microcosms began by collecting water, sediment and aquatic macrophytes from a freshwater pond near Wareham, MA. The narrow leaf pond weed (Potamogeton sp.) was selected as the aquatic maerophyte, based on its abundance and apparent good health when collected. As the pond weed senesced, 800 g of bladderwort (Utricularia ~p) was used as a replacement species prior to dosing based on its health and abundance in conditions similar to those found in the microcosms. Samples of sediment and water were tested for levels of chlorinated, organophosphate and pyrthroid pesticides. No detectable residues levels were found (typically, LOD <0.05 ~tg/L, depending on specific analyte). Sediment was characterized for pH, percent organic matter, cation exchange capacity and textural classification and was found to be a loamy sand (74% sand, 22% silt and 4 % clay). The pH was determined to be 5.5; the organic carbon content was 3.2%; and the CEC was analyzed to be 5.7meq/100 g. 1742

The microcosms were set up approximately eight weeks prior to treatment. Approximately three weeks prior to treatment, 21 Petri dishes of sediment (10 cm diameter by 1.5 cm deep, with 1.0 cm of sediment, 2100 g of sediment) were deployed on the bottom of each test tank. The sediment placed in these dishes was collected from the same location as that used for the maerophytes. This sediment was stored frozen in the interim between collection and use. The number and size of the sediment trays and Petri dishes were selected in order to simulate the same ratio of water to sediment surface area used in model calculations and typical for natural ponds (total sediment mass 152.1 kg) [8, 9 ]. Approximately three weeks prior to initiation of the tests, approximately 500, 60 to 90 day old fathead minnows (l~imephales promelas) were added to each set of spray drift, field runoff and control microcosms. In each treatment tank, the fish were placed in five cages (5 fish per cage) suspended from the top of the tanks to facilitate their removal during sampling. Each control tank received 7 cages with five fish in each. In addition, the remaining fish (412 per test type) were divided among 8 larger cages, four of which were placed into each treatment tank.. Fish from the smaller cages were collected at specified intervals for LSC analyses, and fish from the larger cages were collected for both liquid scintillation counting (LSC) and high performance liquid chromatography (HPLC) analyses. Fine mesh nets were used to transfer fish from the culture unit to a transport vessel and to the cages. Fish were fed every day and observed for mortality. No fish mortality occurred prior to treatment.

Test (?oncentrations and Application For the spray drift test, test materials were applied on August 20, 1990. Deltamethrin was applied at 0.018 Ibs/acre for the spray drift treatment. Based on a microcosm vessel diameter of 1.22 m, 2357 lag of deltamethrin was applied to the spray drift microcosm (nominal concentration 2.208 lag/L). For the spray drift test, tralomethrin was applied at the maximum label rate of 0.024 lbs/acre, an equimolar application to deltamethrin (nominal concentration 2.941 lag/L). To prepare the deltamethrin application to be used in the spray drift treatment, 27.6 mL of a 93.8 lag/mL of 14 C Deltamethrin stock solution was added to a 100 mL amber glass wide mouth bottle. To this was added 103.7 laL of the formulation blank, and the solution was evaporated under a gentle stream of nitrogen to remove the acetone. The resultant solution simulates a Decis 2.5 EC formulation at 25 grams per liter, approximately 0.2 pounds per gallon. 1743

For the spray drift application, tralomethrin was applied at the maximum label rate of 0.024 lbs/acre, an equimolar application to deltamethrin. To prepare the tralomethrin application to be used in the spray drift treatment, 28.8 mL of a 120 lag/mL 14 C Tralomethrin stock solution was added to a 100 mL glass wide mouth bottle. To this was added 95.8 laL of the formulation blank, and the solution was evaporated under a gentle stream of nitrogen to remove the acetone. The resultant solution simulates a Scout 0.3 EC formulation at 0.3 pounds per gallon. Spray drift test solutions were applied uniformly to the surface of the water of their respective microcosms using a pressurized thin layer chromatography spray applicator. To ensure uniform test material was sprayed across the water surface into four equal quadrants. After application, a 110 mL rinse of NANOpure water was applied, followed by 25 mL acetone in order to maximize the amount of test material application. All other tanks were covered during spray delivery to prevent cross-contamination. For the field runoff experiment, test materials were applied to the microcosms on August 28, 1990. Deltamethrin was applied at 0.00576 lbs/acre (759 lag per microcosm; nominal concentration 0.711 p,g/L) and tralomethrin was applied at 0.00768 lbs/acre (1004 lag per microcosm; nominal concentration 0.941 lag/L). These values were 32% of the spray drift values and were intended to simulate a 3.2% runoff from a 10 acre field into a 1 acre pond [8, 9]. To simulate field runoff, test material was adsorbed onto clay and a slurry prepared. The slurry was uniformly delivered immediately below the surface of each microcosm vessel using a separatory funnel. To prepare the deltamethrin application to be used in the field runoff test, 8.90 mL, of the 93.8 lag/mL 14C- deltamethrin stock solution was added to 330 gram clay (100% kaolinite). For the tralomethrin application, 9.20 mL of the 120 ktg/mL 14C- tralomethrin stock solution was added to 330 gram clay. The clay was mixed in a Waring blender for one minute, after which it was transferred to a round bottom flask. The flask was covered with aluminum foil and placed under a gentle stream of nitrogen to evaporate the acetone. After the acetone had been removed, exactly 300 grams of the dosed clay was removed and placed in a 3000-mL volumetric flask. The flask was filled with NANOpure water to the 1,000 mL mark. The remainder of the dosed clay was retained for confirmation of the dose preparation by LSC and HPLC analyses. Slurry was applied to the test vessels using 2 liter separatory funnels, with the funnel mouth held just below the surface of the water. Delivery was performed in a circular manner, to provide a 1744

uniform distribution of slurry in the test vessels and separatory funnels were continuously agitated during application to hold the clay in suspension to ensure a uniform slurry. The control tanks received untreated slurry.

SAMPLING AND ANALYSIS Analyses of the water, sediment, plants and fish removed from the spray drift, field runoff`and control microcosm vessels were conducted using liquid scintillation counting for total ~4C assessment, and with the exception of plant tissue, by high performance liquid chromatography with radiometric detection to determine chemical speciation of 14C labeled compounds. The sampling methods and frequency of sampling are described below. For details concerning the analytical methods used, the reader is referred to [10].

Water Samples of the microcosm water were collected at the following intervals: I hour prior to treatment, and 0.5, 1, 2, 4, 8, 24, and 96 hours after treatment. A final sample was collected 7 days after treatment. Duplicate water samples were collected and analyzed at all times. From 0.5 to 4 hours after treatment, water samples were collected from the treated tanks at depths of 1 -10 cm, 40-50 cm, 80-90 cm (top, middle, and bottom). The pretreatment, 8 hour, 24 hour, 96 hour, and day 7 samples were collected as depth-integrated water samples. A depth-integrated water sample was collected from the control vessels at all sampling intervals. All water samples were two liter in volume, one liter for total 14 C assay and one liter for HPLC analysis with radiometric detection. The latter samples were treated with concentrated hydrochloric acid and extracted with hexane:ethyl acetate (1:1) prior to filtration through sodium sulfate. The extracts were then rotary evaporated and just before dryness, the residue was reconstituted in hexane for HPLC analysis. Samples for the total C14 assay were processed as described above, except that after rotary evaporation, the residue was reconstituted in approximately 5 mL methanol and 15 mL Monophase was added to the scintillation vial. Depth specific samples were removed from each test vessel using a siphon into l-liter volumetric flasks, while depth integrated samples were removed using a glass tube to take a "core" of water. The limit of detection for tralomethrin, deltamethrin and degradates in water was set at 2 ng/L. 1745

Sediment Sediment dishes were collected for analysis prior to test material application and after treatment at the following hours: 1, 2, 4, 24, and 96. A final sample was collected 7 days after treatment. Two dishes were removed from the treatment vessels and analyzed separately for each sample interval; control tanks had only one dish analyzed per sample interval. At each sampling interval, three quality control sediment samples were prepared and analyzed by both LSC for total 14C and HPLC for compound specific analyses. Approximately 100 grams sediment samples were collected from each test microcosm, with duplicate 50 mL subsamples extracted with hexane:acetone (8:2). The limit ofquantitation for tralomethrin, deltamethrin and the degradation products in sediment was set at 50 ng/kg

Biota Five fish were randomly selected from the microcosms for LSC combustion just prior to pyrethroid addition; 1, 2, 4, 24, and 96 hours post-treatment; and 7 days after application. This allowed for five separate 14-C determinations at each sampling interval. In addition, approximately 200 fish were removed from each treatment microcosm vessel at 96 hours after test initiation, with separate extraction and analysis of 100 fish for tralomethrin, deltamethrin and metabolites. Samples were homogenized in a Waring blender and extracted four times with 100 mL hexane/acetone (1:1 ). The hexane layers were combined and analyzed for ~4C residues using HPLC with radiometric detection. The acetone/hexane phases were combined and back partitioned twice with 100 mL hexane. The remaining acetone/aqueous fraction was acidified to pH 2 with concentrated hydrochloric acid and extracted twice with methylene chloride. The methylene chloride extracts were combined with the hexane back partition extracts and analyzed by HPLC-RAM and described as acetone/aqueous extract. The remaining acetone/aqueous extracted was assayed by LSC for non-extractable residues. Finally, the tissue remaining was also quantified for non-extractable residues. The detection limit for each fish sample is dependent upon the counting efficiency and the weight of the fish, thus detection limit varied among samples. The limit of detection ranged from <0.14 to <1.40 ~tg/kg. Macrophytes were sampled prior to test treatment, 24 and 96 hours after treatment, and 7 days after treatment. A portion of plant material (Utricularia sp) from below the water surface was removed from each of the tanks using a clean grappling hook. Whole plant samples were 1746

weighed, blotted dry with paper towels and dried for several days at room temperature prior to subsampling (duplicate 10 g samples) and combustion in a Packard Model 306 Sample Oxidizer. Total 14C content was determined by liquid scintillation counting.

RESULTS AND DISCUSSION Water ( ~oncentrations Depth specific analyses of total 14C residue revealed little differences existed between the various depths of each microcosm vessel. No concentration gradient was apparent even as little as 30 minutes after dosing. Consequently, all calculations were performed with mean concentrations, independent of depth. Tralomethrin spray drift water concentrations of total 14 C-residues (uncentrifuged samples) decreased by 44%, but remained relatively high throughout the seven day period, at 1.78 + 0.180~tg/L 30 minutes after treatment, decreasing to 0.989 + 0.0591ag/L after seven days. The nominal concentration for tralomethrin was 2.94 p,g/L, based on the applied quantity of tralomethrin and the initial volume of water vessels, respectively. At one hour post treatment from the tralomethrin spray drift vessel, the uncentrifuged middle depth samples contained 1.89 _+ 0.071 p.g/L, while the centrifuged samples contained 1.60/ag/L. Similarly, at seven days post treatment, the uncentrifuged integrated depth samples contained 0.989 _+ 0.059lag/L, while the centrifuged samples contained 0.949 lag/L. Total 14C concentration for the control vessel were <0.289rig/L, throughout the time course of the experiment. Tralomethrin field runoff microcosm water concentrations of total 14 C-residues (uncentrifuged samples) remained consistently lower than in the spray drift application throughout the seven day period, at 0.174 _+ 0.0651ag/L 30 minutes after treatment of tralomethrin decreasing to 0.0940 +_ 0.002~,tg/L after seven days. Comparison of centrifuged water concentrations with those of uncentrifuged samples revealed small differences, but larger ones than observed in the spray drift application implying that significant quantities of the applied test materials did not desorb from the applied runoff solids. At one hour post treatment from the tralomethrin vessel, the uncentrifuged integrated depth samples contained 0.122 _+ 0:022 ~g/L, while the centrifuged samples contained 0.0606 ~tg/L (nominal applied concentration 0.94 ~,tg/L). However, at seven days post treatment, the uncentrifuged integrated depth samples 1747 contained 0.0940 lag/L, while the centrifuged samples contained 0.0791 p.g/L, a significantly smaller difference due most likely to settling of the suspended solids. Total suspended solids concentrations were determined to be 50 and 23 mg/L, respectively, for the field runoff and spray drift microcosms after seven days.

Water concentrations are presented for tralome~hrin and its the degradation products, cis- deltamethrin, ct-R-deltamethrin, trans-deltamethrin and Br2CA and are presented in Figures 2 and 3. Tralomethrin rapidly degraded to deltamethrin, with a calculated half-life for tralomethrin of 6.9 hours (determined from time 0.5 to 24 hours). Deltamethrin formed in the tralomethrin application, degraded with a half-life of 81.0 hours (determined from time 24 to 168 hours) to the other products, with BR2CA being the degradative end point for this seven day study. Data for the spray drift deltamethrin microcosm vessel was similar, with 1.11 _+ 0.047~tg/L in the uncentrifuged middle depth water samples at one hour post application, and 1.17 ~tg/L in the comparable centrifuged samples. At seven days post treatment, the uncentrifuged integrated depth samples contained 0.698 + 0.004 p.g/L, while the centrifuged samples contained 0.695 ~tg/L. Water concentrations were 1.160 + 0.058 ~tg/L 30 minutes after the spray drift treatment of deltamethrin decreasing by 40% to 0.698 + 0.004 p.g/L after seven days. Comparison of centrifuged water concentrations with those of uncentrifuged samples revealed small differences, implying that little of the applied test materials were adsorbed to suspended solids. Total suspended solids concentrations were determined to be 69 and 22 rag/L, respectively, for the field runoff and spray drift microcosms after seven days. The nominal concentration for deltamethrin was 2.21 ~tg/L immediately following dosing, based on the applied quantity of deltamethrin and the initial volume of water vessels, respectively. Total 14C concentration for the control vessel were <0.289ng/L, throughout the time course of the experiment. Data from the deltamethrin application, using time 0.5 to 24 hours, corroborated the half-life determined for deltamethrin from the tralomethrin vessel with the result being 18.0 hours. HPLC separation of the products found in water samples was excellent and the use of radiometric detection removed interferences typically associated with UV detection. The degradation profile for deltamethrin under spray drift and field runoff conditions is presented in Figures 2 and 3. In field runoff deltamethrin microcosm, aqueous concentration of total C14 ranged from 0.0937 + 0.013p.g/L in the uncentrifuged middle depth water samples at one hour post 1748

Figure 2. Degradation product water concentrations versus time comparing tralomethrin and

deltamethrin under spray drift and field runoff conditions.

Tralomethrin - Spray Drift Tralomethrin - Field Runoff

60 • ge~me~na • an-|- l~l~w~nl • t¢-INltam~ A o 11,|¢~

250

2O0 30

~ 150 20 ~ loo

5O ~0 ~. _

0 0 -- . i . . .~ ~J~..~ ~ . ~ . ~. ~ . ~ .~ .~ 0 24 48 72 96 120 144 168 24 48 72 96 ~20 144 168 Time (Hours) Time (Hours)

Deltamethrin - Spray Drift Deltamethrin - Field Runoff 5OO

450 v e-II-~el~let~,~ . • I~- I -Dll~Ie~Itheil • t~l)elt~me~la 45 • LC-~It~ ~ ~r~r.~ ~ ,oo ~ ~¢~ A 40 ~" ~so -~ .'oo

~ 250

~ ~oo' ~ 20 .~ ~o

~00 ~

. . . , ...~ -.~ ~.', • [ • ~. ' ...... ~ .],,, ,i ...... ; * 24 48 72 96 120 I~4 168 0 24 48 72 96 ~ 20 10,4 168 Time (Houre) Time (Houre) 1749

Figure 3. Plot of the composition of the 14C residues in the water phase at 168 hours comparing

tralomethrin and deltamethrin under spray drift and field runoff conditions.

100

0~ 80 ~ 70

.2,.o 60 ¢-~ ~ 50 .~ ~ 40

.~ .~ .,~> 30

~ ~0 ~m 0 Tralo Delta Tralo Delta Spray Spray Field Field Drift Drift Runoff Runoff

~ Tralomethrin ['C[Tr[ DeRamethrin ~ a-R-Deltamethrin ~ lrans-De|LamethrJn 1 Br2CA 1750

application, and 0.0442 p-g/L in the comparable centrifuged samples (nominal concentration applied 0.711 p-g/L). At seven days post treatment, the uncentrifuged integrated depth samples contained 0.093 _+ 0.0012 p.g/L, while the centrifuged samples contained 0.0985 p-g/L. HPLC data from the deltamethrin application determined a half-life of 8.1 hours. During the course of this study, 4.02%, 3.07%, 0.92% and 0.99% of total 14-C material was removed by water in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin runoff treatments, respectively. It is estimated that 29.1%, 27.7%, 8.98% and 11.6% of total 14-C material remaining in the aqueous phase at the end of the study, in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin runofftreatments, respectively (Table 1).

Sediment ( ;oncentrations Sediment samples were collected for analysis by both LSC and HPLC at each of the same intervals as the water, with the exception of 0.5 and 8 hours. Results of the LSC analysis for total 14C revealed that the sediment concentrations remained relatively constant throughout the seven day test period. Concentrations of tralomethrin in the spray drift microcosm ranged from 4.40 + 2.44 p-g/kg at I hour post treatment to 16.4 + 15.8 p-g/kg after 96 hours, while those for the deltamethrin spray drift application ranged from to 2.38 + 0.778 p-g/kg after 1 hour post treatment and 12.8 _+ 4.78 p.g/kg at 96 hours, respectively. By 7days, the concentration of tralomethrin had dropped to 11.0 + 2.41 ~tg/kg, whereas the concentration of deltamethrin dropped to 6.82 + 0.863 p.g/kg in the spray drift microcosms. Concentrations oftralomethrin in the runoff microcosm ranged from 15.4 + 15.64 p-g/kg at 1 hour post treatment to 80.7 + 57.06 p-g/kg after 96 hours, while those for the deltamethrin runoff application ranged from to 18.3 _+ 2.55 p-g/kg after I hour post treatment and 63.1 _+ 36.98p-g/kg at 96 hours, respectively. By 7 days, the concentration of tralomethrin was 82.6 + 54.38 p,g/kg, whereas the concentration of deltamethrin was 93.3 _+ 42.07 p,g/kg in the spray drift microcosms. The control microcosms had concentrations of<50 ng/kg throughout the exposure period. Chemical specific analyses by HPLC for the spray drift and runoff microcosms are presented for tralomethrin, deltamethrin, as well as the degradation products, o~-R-deltamethrin, trans-deltamethrin and BR2CA in Tables 2 through 5, respectively. After 1 hour, the tralomethrin 1751

Table 1. Total mass balance for the tralomethrin and deltamethrin spray drift and runoff microcosms removed during experiment and remaining at 168 Hours

Medium Tralomethrin Deltamethrin Tralomethrin Deltamethrin Spray Drift Spray Drift Runoff Runoff (~tg) (~tg) (~g) (~tg) Water 126 72.3 9.23 7.54 removed (4.02%) (3.07%) (0.92%) (0.99%)

Sediment 5.74 3.24 35.2 21.1 removed (0.18%) (0.14%) (3.51%) (2.78%)

Fish 39.0 20.7 2,24 2, 32 removed (1.24%) (0.86%) (0.23%) (0.31%)

Plants 46.3 39.3 5.31 3.98 removed (!.5%) (1.7%) (0.53%) (0.52%)

Water 913 653 90.2 87.1 Remaining (29.1%) (27.7%) (8.98%) (11.6%)

Sediment 34.7 20.7 264 292 Remaining (1.10%) (0.88%) (26.3%) (38.4%)

Plants 285 138 12.4 16.1 Remaining (9,08%) (5.85%) (1.24%) (2.12%)

Adsorbed to 37.2 12.5 3.51 5.19 Vessel Walls (1.19%) (0.53%) (0.35%) (0.68%)

Totals 1487 960 422 435 (47.4%) (40.7%) (42.0%) (57.3%) 1752

Table 2. Sediment concentrations determined by HPLC for the tralomethrin spray drift microcosm vessel

Sampling Tralomethrin cis.Delta. =-R-Delta. tr-Delta. Br=CA Interval (RU25474) (RU22974) (RU23938) (RU26979) (RU23441) (hours) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg)

Pretreatment < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0

1 < 50.0 178 < 50.0 < 50.0 < 50.0 310 327 < 50.0 < 50,0 < 50.0

2 54.8 138 < 50.0 < 50.0 < 50.0 255 414 < 50.0 < 50.0 < 50.0

4 182 353 68.8 < 50.0 < 50.0 485 294 < 50.0 < 50.0 < 50.0

24 650 630 400 < 50.0 < 50.0 169 169 91.3 < 50.0 < 50.0

96 727 1440 739 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50,0 < 50.0

168 206 821 550 < 50.0 177 66.1 355 86,5 < 50.0 < 50.0 1753

Table 3. Sediment concentrations determined by HPLC for the deitamethrin spray drift microcosm vessel

Sampling cis-Delta. ¢z-R-Delta. tr-Delta. Br=CA Interval (RU22974) (RU23938) (RU26979) (RU23441) (hours) (ng/kg) (ng/kg) (ng/kg) (ng/kg)

Pretreatment < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0

1 225 87.1 < 50.0 < 50.0 102 < 50.0 < 50.0 < 50.0

2 150 < 50.0 < 50.0 < 50.0 151 77.6 < 50.0 < 50.0

4 106 < 50.0 < 50,0 <50.0 < 50.0 < 50.0 < 50.0 < 50.0

24 349 113 < 50.0 < 50.0 274 < 50.0 < 50.0 < 50.0

96 1060 520 < 50.0 < 50.0 906 248 < 50.0 < 50.0

168 146 <50,0 < 50.0 111 424 147 < 50.0 106 1754

Table 4. Sediment concentrations determined by HPLC for the tralomethrin field runoff microcosm vessel

Sampling Tralomethrin cis-Delta. =.R-Delta. tr-Delta. Br=CA Interval (RU25474) (RU22974) (RU23938) (RU26979) (RU23441) (hours) (ng/kg) (ng/kg) (ng/kg) (ng/kg) (ng/kg)

Pretreatment < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0

1 1560 684 < 50,0 < 50.0 < 50.0 103 < 50.0 < 50.0 < 50.0 < 50.0

2 2370 12600 <50.0 < 50.0 < 50.0 137 1570 <50,0 < 50.0 < 50,0

4 289 20~0 < 50.0 < 50.0 <50.0 707 3840 < 50.0 < 50.0 < 50.0

24 5090 11000 423 < 50.0 < 50.0 2040 6430 <50.0 < 50.0 < 50.0

96 1600 6190 751 < 50,0 < 50.0 1350 8450 505 < 50.0 < 50.0

168 1060 7950 819 < 50.0 < 50.0 1340 13500 1140 < 50.0 < 50.0 1755

Table 5. Sediment concentrations determined by HPLC for the deltamethrin field runoff microcosm vessel

Sampling c/s.Delta, a-R-Delta, tr-Delta. Br=CA Interval (RU22974) (RU23938) (RU26979) (RU23441) (hours) (ng/kg) (ng/kg) (nglkg) (ng/kg)

Pretreatment < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0 < 50.0

1 297 <50.0 < 50.0 < 50.0 4100 < 50.0 < 50.0 < 50.0

2 1970 < 50.0 < 50.0 < 50.0 543 < 50.0 < 50.0 < 50.0

4 365 < 50.0 < 50.0 <50.0 5390 < 50.0 < 50.0 < 50.0

24 1970 146 < 50.0 < 50.0 692 < 50.0 <50.0 <50.0

96 3030 255 < 50.0 < 50.0 11600 738 < 50.0 172

168 14000 968 < 50.0 < 50.0 8800 707 < 50.0 87.3 1756

spray drift treatment sediment contained 180 + 183.5 rlg/kg tralomethrin, 252.5 + 105.4 rlg/kg cis-deltamethrin, <50.0 rlg/kg ct-R-deltamethrin, <50.0 qg/kg trans-deltamethrin and < 50.0 rlg/kg Br2CA. After 7 days, the tralomethrin spray drift treatment sediment contained 136.1 _+ 98.9 qg/kg tralomethrin, 588.0 + 329.5 rlg/kg cis-deltamethrin, 318.3 + 327.7 rlg/kg ct-R- deltamethrin, <50.0 rlg/kg trans-deltamethrin and 113.5 + 89.8 rlg/kg Br2CA. In comparison, after 1 hour, the tralomethrin field runoff treatment sediment contained 831.5 + 1030.3 rlg/kg tralomethrin, 367.0 _+ 148.3 rlg/kg cis-deltamethrin, <50.0 qg/kg ~t-R-deltamethrin, <50.0 rlg/kg trans-deltamethrin and < 50.0 rlg/kg BrzCA. After 7 days, the traiomethrin field runoff treatment sediment contained 1,470 _+ 183.9 qg/kg tralomethrin, 10,725 _+ 3924.4 rlg/kg cis- deltamethrin, 979.5 _+ 227.0 rlg/kg c~-R-deltamethrin, <50.0 rlg/kg trans-deltamethrin and <50 qg/kg Br2CA (Figure 4). It is clear that tralomethrin degraded to the same degradation products identified for the water phase, but half-life calculations were not possible for the sediment. After 1 hour, the deltamethrin spray drift treatment sediment contained 163.5 _+ 87.0 qg/kg cis-deltamethrin, 68.6 + 26.2 qg/kg c~-R-deltamethrin, <50.0 rlg/kg trans-deltamethrin and < 50.0 rlg/kg Br2CA. After 7 days, the deltamethrin spray drift treatment sediment contained 285.0 + 196.6 rlg/kg cis-deltamethrin, 98.5 _+ 68.6 rlg/kg ~x-R-deltamethrin, <50.0 ~qg/kg trans- deltamethrin and 108.5 + 3.54 rlg/kg Br2CA. In comparison, after 1 hour, the deltamethrin field runoff treatment sediment contained 2,198.5 _+ 2,689.1 rlg/kg cis-deltamethrin, <50.0 qg/kg a- R-deltamethrin, <50.0 qg/kg trans-deltamethrin and < 50.0 rlg/kg BrzCA. After 7 days, the deltamethrin field runoff treatment sediment contained 11,400.0 _+ 3,677.0 rlg/kg cis- deltamethrin, 837.5 + 184.6 rlg/kg ~t-R-deltamethrin, <50.0 rlg/kg trans-deltamethrin and 68.7 + 26.4 rlg/kg BrzCA (Figure 4). The concentrations of deltamethrin remained much more stable in the sediment, and degradation is demonstrated not by loss of parent tralomethrin or deltamethrin, but rather by appearance of a-R-deltamethrin and BR2CA. This may be due to either degradation of adsorbed chemical, or by adsorption of degradation products formed in the aqueous phase. During the course of this study, 0.18%, 30.14%, 3.51% and 0.2.78% of total 14-C material was removed by sediment in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin runoff treatments, respectively. It is estimated that 1.10%, 0.88%, 26.3% and 38.4% of total 14-C material remaining in the sediment phase at the 1757

Figure 4. Plot of the composition of the 14C residues in the sediment at 168 hours comparing

tralomethrin and dcltamethrin under spray drift and field runoff conditions.

1 O0

0m 80 ~; ~ 70

-~.~o 60 .~ •r~ 50 .~ ~ 40 L" "~ 30

e 20

'~ ~0

0 I ~ ! Tralo Delta Tralo Delta Spray Spray Field Field Drift Drift Runoff Runoff

B Tralomethrin ~ DeRamethrin [~ a-R-Deltamethrin ~ trans-Deltamethrin ~ Br~CA 1758

end of the study, in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin rtmofftreatments, respectively (Table I ).

( ?oncentrations in Biota Fathead minnows were removed and analyzed at several intervals during the seven day study, and data for total ~4 C analysis of tissue (on a wet weight basis). Concentrations of ~4C residues in fish removed from the tralomethrin spray drift microcosm vessel were 374 ± 124 ~tg/kg on day four, and 312 ± 62/ag/kg on day seven. Bioconcentration factors (BCF) were calculated by dividing these tissue concentrations by the water concentrations at the same respective intervals. Bioconcentration factors determined in this manner were 219X for day four and 315X for day seven. It should be noted, however, that the BCFs were not generated under constant exposure conditions and may not represent steady-state values. Extraction and analysis by HPLC of extra fish tissue removed on day four revealed that 14C tissue residues were largely metabolized in the fathead minnows removed from the tralomethrin spray drift microcosm (Tables 6 through 9). The tissue contained 21.4 lxg/kg S-

tralomethrin, < 0.1 p,g/kg R-tralomethrin, 1.11 p.g/kg cis-deltamethrin, 32.7 lag/kg a-R- deltamethrin, 63.1 tag/kg trans-deltamethrin and 14.3 ~tg/kg Br2CA. Mass balance, calculated for the extraction and analysis of this tissue sample was 90.4%, with 83.6% removed in the extraction process and 6.4% non-extractable from the tissue. The bioconcentmtion factor determined for the tralomethrin spray drift can be adjusted for the compound specific analysis of tissue removed at hour 96. The tissue removed on day four contained 21.4 ~g/kg tralomethrin, with a corresponding water concentration of 18.4 ng/L traiomethrin. The BCF determined in this manner is 1200X, slightly higher than that determined using total ~4C residue concentrations. In comparison, concentrations of ~4C residues in fish removed from the tralomethrin runoff microcosm vessel were 15.4 :~ 4.0 p.g/kg on day four, and 13.4 ± 4.7/ag&g on day seven. Bioconcentration factors (BCF) calculated by dividing these tissue concentrations by the water concentrations at the same respective intervals were determined to be 185X for day four and 143X for day seven. Extraction and analysis by HPLC of extra fish tissue removed on day four revealed that 14C tissue residues were largely metabolized in the fathead minnows removed from the tralomethrin field runoff microcosm. The tissue contained 0.875 ~tg/kg S-tralomethrin, < 0.1 1759

Table 6. Total "C tissue concentrations for fathead minnows removed from the tralomethrin spray drift mierocosm vessel, based on the specifie activity of tralomethrin

Sampling Total 14C Interval Concentration Average (hours) (~g/kg) (#g/kg)

Pretreatment < 0.505 < 0.563 < 0.365 < 0.650 < 0.717 n = 5 < 1.10

0.5 NS

1 22.3 28.2 13.6 23.4 20.2 n = 5 32.7

22.1 14.3 46.9 33.2 33.5 n = 5 49.4

41.2 93.2 41.4 55.2 34.2 n =5 66.0

8 NS NS

24 162 22O 308 233 206 r~--5 287

96 465 285 223 374 373 n = 5 523

168 217 296 312 380 n=5 313 352

NS - Not scheduled to be sampled. NOTE - The detection limit for each fish is dependent upon the counting efficiency and the weight of the fish. Due to differences in these values, the detection limits vary among fish. 1760

Table 7. Total ~4C tissue concentrations for fathead minnows removed from the deltamethrin spray drift microcosm vessel, based on the specific activity of deltamethrin

Sampling Total 14C Interval Concentration Average (hours) (~g/kg) O~g/Icg)

Pretreatment < 0.617 < 0.437 < 0,241 < 0.446 < 0,353 n = 5 < 0.584

0.5 NS NS

1 34.1 29,8 36.7 29.3 30,4 n = 5 15.6

71.3 74.3 58.2 67.8 57.9 n = 5 77.2

56.3 57.5 70.6 67.7 80.0 n = 5 73.9

8 NS NS

24 186 172 207 194 200 n =5 207

96 148 106 152 161 200 n=5 199

168 130 132 122 129 127 n = 5 134

Table 8. Total 14C tissue concentrations for fathead minnows removed from the tralomethrin runoff microcosm vessel, based on the specific activity of tralomethrin

Sampling Total 14C Interval Concentration Average (houra) ~g/kg) (.ug/kg)

Pretreatment 1.37 = 2.20" 0.803`= 1.27 0.963" n=5 0.990"

0.5 NS NS

1 1.81 0.417 1.69 1.55 1.30 n=5 2.55

2.10 1.07 1.08 1.99 4.91 n = 5 0.803

1.37 1.63 2.68 2.51 2.33 n = 5 4.56

8 NS NS

24 19.7 7.81 23.7 18.1 18.7 n=5 20.8

96 10.3 13.1 17.3 15.4 15.7 n = 5 20.7

168 15.0 14.1 19.7 13.4 7.14 n = 5 11.0

NS - Not scheduled to be sampled.

NOTE - The detection limit for each fish is dependent upon the counting efficiency and the weight of the fish. Due to differences in these values, the detection limits vary among fish.

" - Control contamination is suspected to have occurred during sample handling. The contamination is insignificant compared to the number of dpm measured in the treatment samples. 1762 Table 9. Total ~4C tissue concentrations for fathead minnows removed from the deltamethrin runoff microcosm vessel, based on the specific activity of deltamethrin

Sampling Total 14C Interval Concentration Aversge (hours) (.u.g/kg) (p.g/kg)

Pretreatment 0.394" 0.633= 0.538= 0.492 0.620 = n=5 0.277"

0.5 NS NS

1 1.14 1.09 0.981 1.08 0.898 n = 5 1.28

1.43 1.43 1.06 1.31 0.999 n = 5 1.65

3.89 3.43 3.94 4.02 3.95 n = 5 4.89

8 NS NS

24 12.5 10.5 10.3 14.4 11.3 n = 5 27.5

16.5 12.3 16.1 15.9 15.7 n = 5 18.8

168 13.4 14.1 13.9 15.5 17.2 n = 5 18.8

NS - Not scheduled to be sampled.

NOTE - The detection limit for each fish is dependent upon the counting efficiency and the weight of the fish. Due to differences in these values, the detection limits vary among fish.

= - Control contamination, is suspected to have occurred during sample handling. The contamination is insignificant compared to the number of dpm measured in the treatment samples. 1763 ~tg/kg R-tralomethrin, 3.31 Bg/kg deltamethrin, 0.940 ~tg/kg o~-R-deltamethrin, < 0.1 p.g/kg trans-deltamethrin and 0.123 Bg/kg Br2CA. Mass balance, calculated for the extraction and analysis of this tissue sample was g8.9%, with 77.4% removed in the extraction process and 10.7% non-extractable f~om the tissue. Concentrations of 14C residues in fish removed from the deltamethrin spray drift microcosm vessel were 161 ± 40 pg/kg on day four, and 129 ± 5 p.g/kg on day seven. Bioconcentration factors (BCF) were calculated by dividing these tissue concentrations by the water concentrations at the same respective intervals. Bioconcentration factors determined in this manner were 26OX for day four and 185X for day seven. Extraction and analysis by HPLC of extra fish tissue removed on day four revealed that 14C tissue residues were largely metabolized in the fathead minnows removed from the deltamethrin microcosm vessel. The tissue contained 69.1 Bg/kg deltamethrin, 19.5 ~tg/kg ~-R deltamethrin, 40.4 p.g/kg trans-deltamethrin and 7.16 ~tg/kg Br2CA. Mass balance, calculated for the extraction and analysis of this tissue sample was 91.9%, with 78.6% removed in the back extraction process, and 12.1% nonextractable from the tissue. The bioconcentration factor determined for the deltamethrin spray drift can be adjusted for the compound specific analysis of tissue removed at hour 96. The tissue removed on day four contained 69.1 ~tg/kg deltamethrin, with a corresponding water concentration of 43.3 ng/L deltamethrin. The BCF determined in this manner is 1600X, higher than that determined using total 14C residue concentrations. In the field runoff microcosm, concentrations of 14C residues in fish removed from the deltamethrin microcosm vessel were 15.9 ± 2.3 ttg/kg on day four, and 15.5 ± 2.4 Bg/kg on day seven. Bioconcentration factors (BCF) were calculated by dividing these tissue concentrations by the water concentrations at the same respective intervals. Bioconcentration factors determined in this manner were 169X for day four and 166X for day seven. Extraction and analysis by HPLC of extra fish tissue removed on day four revealed that 14C tissue residues were also largely metabolized in the fathead minnows removed from the deltamethrin microcosm vessels. The tissue contained 2.82 i~g/kg deltamethrin, 3.59 ktg/kg ct-R deitamethrin, 1.37 ILtg/kgtrans-deltamethrin and 0.108 ~tg/kg Br2CA. Mass balance, calculated for the extraction and analysis of this tissue sample was 89.1%, with 58.0% removed from the tissue in the hexane extract, 14.3% removed in the back extraction from acetone (aqueous) 1764

extract, 0.2% not able to be back extracted from the acetone (aqueous) extract and 16.5% nonextractable from the tissue. The bioconcentration factor determined for the deltamethrin field runoff can be adjusted for the compound specific analysis of tissue removed at hour 96. The tissue removed on day four contained 2.82 ~tg/kg deltamethrin, with a corresponding water concentration of 14.7 ng/L deltamethrin. The BCF determined in this manner is 192X, similar to that determined using total 14C residue concentrations. Figure 5 presents the distribution of metabolites extracted from fathead minnow tissues at 168 hours comparing tralomethrin and deltamethrin under spray drift and field runoffconditions. During the course of this study, 1.24%, 0.86%, 0.23% and 0.3 t% of total 14-C material was removed by fish in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deitamethrin runofftreatments, respectively (Table 1). Macrophytes were collected at pretreatment and days one, four and seven after application. Total 14 C plant tissue concentrations are compared for tralomethri and deltamethrin under spray drift and field runoff conditions in Table 10. On a dry weight basis, concentrations of 11.1 mg/kg, 14.2 mg/kg and 17.9 mg/kg were obtained for days one, four and seven, respectively in the tralomethrin spray drift microcosm, whereas, concentrations of 1.42 mg/kg, 1.24 mg/kg and 0.779 mg/kg were obtained for days one, four and seven, respectively in the tralomethrin field runoff microcosm. In the spray drift microcosm, concentrations appeared to increase with time, whereas in the field runoff microcosm, concentrations in macrophytes did not appear to increase with time. Based upon dry weights and the total 14C water concentrations, accumulation factors were calculated for day seven to be 18,200X. and 8,290X, for spray drift and field runoff treatments, respectively. In comparison, on a dry-weight basis, concentrations of 7.03 mg/kg, 12.7 mg/kg and 8.69 mg/kg were obtained for days one, four and seven, respectively in the deltamethrin spray drift microcosm, whereas, concentrations of 1.02 mg/kg, 1.05 mg/kg and 1.01 mg/kg were obtained for days one, four and seven, respectively in the tralomethrin field runoff microcosm. Based upon dry weights and the total 14C water concentrations, accumulation factors were calculated for day seven to be 12,400X. and 10,700X, for spray drift and field runoff treatments, respectively. This data indicates that plant tissue present in aquatic systems significantly removes pyrethroids from the water column. During the course of this study, 1.5%, 1.7%, 0.53% and 1765

Figure 5. Plot of the composition of the 14C residues in the fish tissue at 168 hours comparing

tralomethrin and deltamethrin under spray drift and field runoffconditions.

1 O0

~ 80

~ 7o .2,~ 60 ~ 50

~" ~,o ~-. ~ 30 m~ 20 ~: ~0 im 0 I Tralo Delta Tralo De'Ita Spray Spray Field Field Drift Drilt Runoff Runoff

~ Tralornethrin ~ Del~ame~hrm ~ a-R-Deltemethrin ~ trans-DeRamethrin m BrzCA 1766

Table I0. Total 14 C plant tissue concentrations (pg/kg) for tralomethrin and deltamethrin under spray drift and field runoff condition~, based on their respective specific activities

Sampling Tmlomethrin Deltamethrin Tmlomethrin Deltamethrin Interval (hr) Spray Dri~ Spray Drit~ Field Runoff Field Runoff

Pretreatment 15.1 <3.85 19.5 8.26

24 II100 7030 1420 1020

96 14200 12700 1240 1050

168 17900 8690 779 I010

n.b. The detection limit for each sample is dependent upon the counting efficiency and the weight of the sample. Due to difference in these values, the detection limit vary. 1767

0.52% of total 14-C material was removed by plants in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin runoff treatments, respectively. It is estimated that 9.08%, 5.85%, 1.24% and 2.12% of total 14-C material was remaining in plant material at the end of the study, in the tralomethrin spray drift, deltamethrin spray drift, tralomethrin field runoff and deltamethrin runoff treatments, respectively (Table 1). Tralomethrin is rapidly converted to deltamethrin, with a half-life of 12.7 hours under spray drift conditions and 6.8 hours under simulated runoff conditions, and then converted to less active isomers and then to decamethrinic acid (BrzCA). After 24 hours, the percent radioactivity of tralomethrin was 25% of the test material in the water column. This same degradation pattern was observed for deltamethrin, as well. Concentrations of pyrethroids in water are also dependent upon the mechanism of its addition to water. Other researchers have measured declining aqueous concentration of deltamethrin over time in pond environments [11,12]. The rapid initial loss of pyrethroids in ponds is generally attributed to volatilization from the surface water and sediment and plant adsorption. In this study, approximately 50-60% of the 14-C material is unaccounted for and presumed to have volatilized. Partitioning of pyrethroids among water, plants, sediment and fish is a function of the method of introduction into the microcosm system. Spray drift applications of deltamethrin yielded water concentrations that remained at or near the nominally applied dose (based on total 14C residue concentrations). The sediment was an important but not the primary sink for applied pyrethroid under simulated spray drift application, however, approximately 30-40% of the 14-C material was associated with sediment in the field runoff microcosms. For tralomethrin, concentrations in sediment reached a maximum concentration 96 hours after application and decreased to approximately 30% of the maximum by 168 hours. Conversely, when deltamethrin was applied simulating an agricultural runoff, water concentrations were lower, and the mass dissolved in the water did not represent the major fraction of applied residues. Once associated with sediment, pyrethroids tended to stay sorbed. In sediment, tralomethrin was immediately converted to deltamethrin. Plant tissue was found to significantly accumulate pyrethroids, with higher accumulation factors noted in spray drift treatments. Pyrethroid concentrations in fish are dependent on the method of introduction into the microcosm and is related to aqueous concentrations. 1768

Acknowledgment - This study was sponsored by Hoecht-Roussel Agri-Vet, Somerville, N.]. Than~" to the staff of Springborn Laboratories, Inc..for their assistance. REFERENCES

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