Distribution of Insecticides Sprayed by Airplane on an Irrigated Corn

11 Distribution of Insecticides Sprayed by Airplane on an Irrigated Corn Plot

Downloaded by EAST CAROLINA UNIV on December 24, 2017 | http://pubs.acs.org Publication Date: June 1, 1966 | doi: 10.1021/ba-1966-0060.ch011

E R V I N H I N D I N , D O N A L D S. M A Y , 1 and G I L B E R T H . D U N S T A N College of Engineering, Research Division, Washington State University, Pullman, Wash.

The distribution of insecticides applied once to an irrigated plot was investigated. Samples of crop, soil, air, water applied, irrigation runoff water, and water-borne settleable silt were collected prior to insecticide application and periodically thereafter for the remainder of the growing season. Insecticide residues in the extracts of the samples taken were determined. DDT and diazinon were applied during the first year; DDT and ethion were used during the second. Thirty-five percent of the DDT and diazinon was found at tassel height during 1963. In 1964, 22% of the DDT and ethion were found at this level. The relationship, plant to crop, varied throughout the growing season. Less than 0.01% of the insecticides applied was removed by the runoff water and water-borne silt.

The fate of insecticides once applied to cropland is not completely known. Available fragmentary evidence indicates that surface drainage from croplands treated with insecticides may contaminate the aquatic environment; however, relatively little is known about the transport of these insecticides through surface drainage. Nicholson (9) found toxaphene and the gamma isomer of B H C in a stream draining an insecticidetreated cotton area. I n another study Nicholson et al. (10) evaluated the effect of parathion and other insecticides used i n peach culture on the water quality of a pond adjacent to the orchard. Parathion was found in the pond water in concentrations of 0.02 /xgram/liter, the pond bottom mud at 1.9 /xgram/kg., and in the orchard soil at 1.7 /xgram/kg. Present address: Water Pollution Control Administration, Department of the Interior, Corvallis, Ore.

132 Rosen and Kraybill; Organic Pesticides in the Environment Advances in Chemistry; American Chemical Society: Washington, DC, 1966.


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The presence of parathion in the pond water and pond bottom muds was attributed to insecticide-laden soil washed in during a period of accelerated erosion. One-hundredth /*gram per liter of parathion, 0.02 yugram per liter of D D D , and 0.01 /*gram per liter of B H C were found in the pond water 4 months after the last application of insecticides. Dunstan, Proctor, and H i n d i n (2) reported the presence of D D T , aldrin, and the isopropyl ester of 2, 4-D in a number of irrigation return flow wasteways in the Columbia Basin Project of Eastern Washington. Numerous reports indicate the distribution and persistence of chlorinated organic insecticides in soil. Ginsburg (3) found most of the accumulated D D T i n the soil layer corresponding to cultivation or plow depth. Rodenheser ( I I ) reported that in a study conducted i n 1952, D D T and aldrin were initially in soil in concentrations of 38 and 140 mg. per kg., yet 6 years later 28 mg. per kg. of D D T and 95 mg. per kg. of aldrin were found in the same soil. Taschenberg, Mac, and G a m brell (14) found the accumulation of D D T in the soil resulting from three to four applications per year for 6 years to be approximately 9 p.p.m. and over a 12-year period to be approximately 13.5 p.p.m. About half of the D D T applied over the 6-year period and two thirds of that applied over the 12-year period were not recovered from the soil. D D E and D D T ratios were higher in the soils receiving applications over the 12-year period. Clore et at (1) conducted a study i n which five plots received applications of varying concentrations of D D T . A n average of 70, 68, 47, 15, and 19% of the D D T present in the soil during the first year was present in the soil in the second, third, fourth, sixth, and ninth year, respectively. The more D D T applied initially, the greater the percentage remaining on the soil i n subsequent years. Lichtenstein and Schultz (7) found that the persistence of aldrin in soil depended largely on the presence of water in the soil. They concluded that once aldrin had been displaced by water from the soil particles, a major part of the insecticide was lost by volatilization. U n like aldrin, D D T d i d not respond to displacement by water nor was it affected by enlargement of the surface onto which it had been deposited. Under field conditions, daily disking of a treated loam soil reduced 3 8 % of the aldrin residue and 2 5 % of the D D T residue after 3 months. In another study, Lichtenstein et al. (6) were able to recover aldrin and heptachlor residues ranging from 2.7 to 5.3% of the applied dosage 4 months after application to the soil surface. The persistence increased by a factor of 10 when the insecticides were mixed with the soil by rotatilling. One year after application 90% of the recovered insecticides was found in the upper 3 inches of the soil. Because two to three times more insecticide residues were recovered from cropcovered plots than from fallow ones, it was concluded that a dense

Rosen and Kraybill; Organic Pesticides in the Environment Advances in Chemistry; American Chemical Society: Washington, DC, 1966.


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cover crop increased the insecticide persistence by reducing volatiliza tion at the soil-air interface. F r o m the literature cited it can be concluded that about 9 0 % of the recoverable D D T residue w i l l reside i n the top 3 inches of the soil or at cultivation or plow depth. Certain persistent insecticides can be removed from the soil through volatilization. The extent of volatiliza tion is determined in part by the vapor pressure of the insecticide, by displacement from the soil particle by other substances, by the presence and type of cover crop, and by the "turning over" of the soil. Insecticides from treated areas can enter the surface water sorbed onto eroded soil particles and/or desorbed from the soil by water. Experimental

Plan

A plot measuring 1 acre at the Othello Research Farm of the Irri gated Agricultural Research and Extension Center, 10 miles east of Othello, Wash., was assigned for use. To avoid boundary effects and to facilitate installation of equipment for flow measurements, a section measuring 0.46 acre was used for the study. The Research Unit lies within the rain shadow of the Cascade M o u n tains of Washington. The average yearly rainfall of the area is 9.00 inches, only about 8% of which falls from mid-June to mid-September. D u r i n g the same 3 months the rate of evaporation is three times as great as the average annual rainfall. Because of this and the low intensity of the rainfall, surface runoff occurs only from the shallow layer above the frost line. The plot soil, of loessial origin, is a coarse silt loam belonging to the Shano series. The top soil, very fine and powdery, is high in inor ganic nutrients and low in organic matter. The plot was irrigated down a 1.88% slope, having been cropped for only 3 years. The entire plot was planted with Idahybrid-330 corn and culti vated and irrigated according to established agricultural practices. C u l tivation was continued until the corn began to tassel. The crop was irrigated approximately every 10 days up to the time the corn began to mature. The irrigation water was Columbia River water conveyed to the station through the projects east low canal. Sampling Sites

A careful examination of the topography of the plot determined the best site for the location of the return flow measuring equipment and aided i n the selection of sampling sites. The plot assigned was 100 by approximately 435 feet. A square section of the plot (1225 sq. feet at the corner of the lowest elevation) was used for the installation of the return flow measuring equipment and construction of two bypass drain age ditches and one ditch draining the test area. To avoid boundary effects, a section of the plot measuring 50 χ 400 feet was used. Soil samples were taken at 50-foot intervals from rows 3, 7, 11, and 15. (The location of the sampling sites was recommended by T. S.



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Russell, statistician for the Washington Agricultural Experiment Station.) In addition a series of seven samples (same intervals in the row) was taken from a row *4 mile from the test plot, and constituted the control. The soil characteristics of the control were the same as those of the test area. The same variety of corn was planted i n the control area as in the test area. As far as was known, the control area was free of insecticides. Sampling was duplicated within the test area by shifting the starting point from the 50-foot point to the 25-foot point and to rows 2, 6, 10, and 14. Samples from these sites were held in reserve if it became desirable to collect additional data. To estimate the actual amounts reaching the plant and reaching the ground, a series of glass plates was installed, prior to spray application, at 11 locations selected at random within the test area. The plates were 1 sq. foot and installed on tripods at tassel height 8 feet above ground level. One aerial installation was placed in the control row to determine the extent of insecticide drift. The apparatus used to sample the air for pesticides was placed in the center of the plot. The air intake was at tassel height. Water meters were installed on the irrigated risers at the head of the plot to measure the water applied; each riser supplied water to two rows. Equipment to measure, proportionally divert, and collect the surface runoff was installed at the end of the irrigation ditch-draining test plot. The measuring apparatus consisted of an up-channel and apron, Parshall flume, stilling well, and water level recorder. A flow-splitting device was attached to the downstream side of the flume. One third of the flow was diverted to a settling tank where it was sampled. A 3-hour retention time was allowed for the water-borne silt to settle. A proportional part of the settleable silt was collected for analysis. To eliminate errors caused by insecticide spray falling into the collection ditch and onto the flow measuring and sampling equipment, sheets of plastic film were used to cover the installations during insecticide application. Insecticide

Application

Two insecticides—DDT and diazinon—were used in the 1963 studies, while D D T and ethion were used during the 1964 growing season. D D T in the form of an emulsifiable -2 E M D D T ( A l l i e d Chemical C o . ) , diazinon as emulsifiable 4 E diazinon (Geigy Chemical Co.) and ethion as emulsifiable 4 E ethion (Niagara Chemical Co.) were applied at the rate of 2, 1, and 1 pound of active insecticide per acre, respectively. A Stearman 450 airplane, equipped with 32 spray nozzles and 46 plates having D-8s and D-lOs orifices, was used to apply the insecticides. Two 45-foot swaths were made over the test area on each of 3 days during the 1963 study. During the 1964 season only one application consisting of two swaths was made. Applications were made at 7:00 p.m. on each day.


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Collection and Analysis

S o i l . The soil was sampled at the sites as described. E a c h sample consisted of a shallow block of soil taken by a specially designed scoop. The block had a surface area of 30 sq. inches, was 2 inches deep, and had a dried weight of approximately 1 kg. The block was placed in a paper bag and allowed to air-dry prior to insecticide extraction. Soil samples were taken prior to application, 1 day after the last application and 7 days after the last irrigation. The soil samples at a particular site were taken 3 inches from each other—e.g., at site 10, on July 29, 1963, a soil block was taken 100 feet from the head of the furrow; on August 8, 1963, the block was taken 100 feet 3 inches from the head of the furrow; and on September 5, 1963, the block was taken 99 feet 9 inches from the head of the furrow. Each block location was set off from the other by 4 inches. The insecticides were extracted using a method developed by the Agricultural Division of the Shell O i l Co. (13). EXTRACTION PROCEDURE. Approximately 1 kg. of the air-dried soil was blended with two 500-mg. portions of petroleum naphtha at 2500 r.p.m. for 30 minutes. The extracts were filtered through cheese cloth and then through No. 5 Whatman filter paper. The filtrate was sent through a column of anhydrous sodium sulfate to remove all traces of moisture. The filtrates were combined, and the solvent was removed by rotary vacuum evaporation carried out at 35°C. to a volume of approximately 4 ml. The concentration extract was transferred to a 10-ml. vial. Two 2.5-ml. portions of petroleum naphtha facilitated the transfer. The concentrate was evaporated to dryness using a stream of cool, dried air. One-half-milliliter portions of petroleum naphtha were used to rinse down the walls of the vial. A t time of analysis the residue was taken up i n a measured amount (1 or 0.1 ml.) of petroleum naphtha. In previous studies (4) it was found that 22.5% of either of the insecticides from Shano type soil is recovered using the above-mentioned extraction procedure. This value was rechecked periodically during the study and found to be consistent.

Water. The water used for irrigation was sampled at the diversion box while the section was being irrigated. During the 1963 study, the carbon adsorption method suggested by Middleton (8) was used to sample the water. PROCEDURE. A measured amount of water, optimum quantity 5000 gallons (18,925 liters), was pumped through a column of Nuchar C-190, 30-mesh activated carbon 3 inches in diameter by 18 inches in height. The pumping rate used was 0.5 gallon per minute. After collection, the carbon was removed from the filter, air-dried, and placed in a modified Soxhlet extractor to remove the organic matter by benzene. Except for 250 ml., all solvent was removed by distillation. The remaining solvent was further reduced to approximately 4 ml. by rotary vacuum évapora-



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tion. The method of transfer and evaporation to dryness described for the soil extradants was used for the carbon extracts. Rosen and Middleton (12) found that a 7 5 % recovery of D D T can be anticipated using the above-mentioned adsorption and subsequent desorption procedures. Investigations carried out by H i n d i n (4) confirm the fact that 7 5 % of D D T and 7 5 % of diazinon can be recovered. The data for D D T in water are corrected for the 7 5 % recovery. The irrigation return flow from the rills drained into a ditch; then was conveyed to the flow-measuring equipment. The flow after being measured was split proportionally. One third of the flow was diverted to a settling basin, where the settleable matter in the return flow was removed. The water in the settling basin was pumped through activated carbon and treated i n the same manner as the irrigation water. During the 1964 study a 18-liter composite sample of the irrigation water was taken. The insecticides were removed and concentrated using the extraction method of Teasly and Cox (15). METHOD. One liter aliquots was extracted twice with 500 ml. of 1 to 1 ethyl ether-petroleum ether mixture. The combined extract was evaporated as described for the deadsorbant from the carbon adsorption method. Settleable Water-Borne Silt. Wide-mouthed jars having an opening of known area were placed at the bottom of the settling basin to collect settleable silt. Three hours after the irrigation flow had ceased, the jars were removed, the excess water in the jars was decanted, and the settled silt was allowed to dry. The air-dried silt was weighed and treated in the same manner as a soil sample. Spray Solution. Prior to each application of insecticides, 250 m l . of the spray solution were removed from the airplane's spray solution and analyzed directly by gas chromatography. Aerial Plates. The insecticides adhering to the aerial and surface plates were removed by rinsing the plates with three 50-ml. portions of petroleum naphtha. The rinsings were collected and evaporated in the same manner as the filtered soil sample extracts. Plants. To remove the insecticide residue on the plant, the plant sample was chopped, and the insecticide residue was extracted with 1 0 % acetone in petroleum naphtha. The crop-solvent was placed in a 1-gallon press-top can with stainless steel baffles and rotated at 45 r.p.m. for 30 minutes. The solvent was decanted off, and the sample was extracted once again. The combined extracts were filtered through filter paper and evaporated in the same manner as the soil extract. Where lipid material was present, the corn extracts were re-extracted with acetonitrile. A i r Sampling. The apparatus used to sample insecticides i n the air consisted of an insulated box housing two Smith-Greenburg impingers. A small battery operated the air pump and was used to draw a sample of air at the rate of 0.044 cu. meter per minute through n-decane contained in the impinger. The sampling period lasted 1 hour.


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Analysis

Extracts from all samples were analyzed by gas chromatography as described by H i n d i n , M a y , and Dunstan (5). After the residue had been taken up in a measured volume (0.1 or 1.0 ml.) of petroleum naphtha, a 10-/Jiter aliquot was injected into a Beckman temperature programmer coupled with a Dohramann microcoulometric titration detector. The column-packing material used for the separation of the insecticides was 5 % by weight of E P O N 1001 on 60/80-mesh acidwashed, flux-calcined diatomite (Chromosorb P ) . This material was packed in aluminum tubing *4 inch i n o.d. by 3 feet. To separate chlorinated organic compounds, a column temperature of 225°C. and a nitrogen carrier gas flow of 75 m l . per minute were used. The coulometer was operated at maximum sensitivity (512 ohms), at a damping position of 4 and a bias of 250. A silver-silver ion cell was used. To separate sulfur-containing organophosphate insecticides, a column temperature of 180°C. and a nitrogen carrier gas flow of 39 ml. per minute were used. The coulometer was operated at maximum sensitivity (512 ohms) at a damping position of 4 and a bias of +100. A n iodine-iodine ion cell was used. Three standard solutions were prepared—one containing 1 mg. of D D T and 1 mg. of D D D per 10 ml. of solvent; the second containing 1 mg. of diazinon per 10 m l . of solvent; and the other containing 1 mg. of ethion per 10 ml. of solvent (benzene). The retention time (time required after injection of the sample for the component to reach its maximum peak height) was used as a qualitative measure to identify the component. Quantitative information was obtained from the direct relationship of the concentration of insecticide to the maximum peak height. Standards were analyzed periodically during the analysis of the residues. Results

The test area was irrigated according to irrigation practices used in the Columbia Basin project area, where a 25 to 3 3 % runoff flow from irrigated fields can be anticipated. Table i is a compilation of the results obtained from the flow measurements of the irrigation water applied and the runoff water. Each irrigation lasted for 16 hours. The average percentage of runoff exceeded the maximum anticipated value in 1963 but was slightly less than the minimum value in 1964. The quantity of water-borne silt removed by the irrigation water appears in Table II. The concentrations of insecticide residues in the plants, soil, water, settleable silt, and air during the 1963 and 1964 investigations are shown in Tables III and I V , respectively. Samples taken from the airplanes' spray tank prior to each application in 1963 revealed 0.26, 0.14, and 0.30 pound of D D T per gallon.


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Table I. Flow Data Water Applied, Acre-Inches

Date 7/29-30/63 8/8-9/63 8/17-18/63 8/28-29/63


Av„ 1963 8/7-8/64 8/15-16/64 8/22-23/64 8/29-30 9/6-7/64 9/12-13/64 Av., 1964

Runoff Water, Acre-Inches

% of Flow Returned

3.93 5.43 4.35 5.24

1.6 2.21 1.84 2.04

40.9 40.7 43.5 38.9

4.74

1.93

40.8

4.02 3.54 3.62 3.14 2.96 2.38

0.66 0.36 0.98 0.64 0.88 0.66

16.4 10.1 25.9 29.9 29.7 27.7

3.28

0.75

23.3

Eight gallons of each spray solution were applied per application. The calculated amount of D D T sprayed was 5.6 pounds per acre over the test area. Because of analytical difficulties, the calculated amount of diazinon could not be determined. During the 1964 season, when one application of insecticide mixture was made, the spray solution was found to contain 0.25 pound of D D T and 0.125 pound of ethion per gallon. Eight gallons of the spray solution were applied: 2 pounds of D D T and 1 pound of ethion per acre. The aerial plates at tassel height revealed that only 1.67 pounds of D D T and 0.98 pound of diazinon had reached that level. During the 1964 spray application, 0.44 pound of D D T and 0.49 pound of ethion were found at tassel height. Based on the data obtained, the distribution of insecticides on the pound per acre basis can be determined (Tables V and V I ) . Table II. Silt Data Date

Silt Removed, Kg./Acre

8/8-9/63 8/17-18/63 8/28-29/63

18.8 6.7 4.7

8/7-8/64 8/15-16/64 8/22-23/64 8/29-30/64 9/6-7/64 9/12-13/64

12.3 22.2 15.1 8.7 5.4 3.3


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Table III· Concentration of Date

Insecticide

Plant Test section, Control, mg./plant* mg./plant

0

< 0.01 < 0.01


7/29-30/63, DDT 4 days prior to application Diazinon 8/8-9/63, DDT 1 day after last application Diazinon 8/17-18/63, 10 days after application

DDT Diazinon

8/28-29/63, 21 days after application

DDT Diazinon

9/5/63, 30 days after application

DDT Diazinon

b

b

9.2 ± 3.1 0.07 ± 0.05

4.8 ± 1.9 0.12

< 0.01 < 0.01

b

b

< 0.01 < 0.01 * b

< 0.01 < 0.01

b

b

* Averaged value, 30-sq. inch block. Less than sensitivity of detected method. b

Conclusions Not a l l of the insecticides applied could be detected at tassel height. Thirty percent of the D D T and 3 5 % of the diazinon were found 8 feet Table IV. Concentration of Time

Insecticide

Plant Test section, Control, mg./plant mg./plant a

a

< 0.01 < 0.01

7 days prior application

DDT Ethion

< 0.01 < 0.01

12 hr. after application

DDT Ethion

1.6 0.6

< 0.01 < 0.01

7 days after application

DDT Ethion

1.0 0.2

< 0.01 " < 0.01


DDT Ethion


DDT Ethion


DDT Ethion

0.6 < 0.01

b

b

b

h

b

b

b

b

< 0.01 < 0.01

* Averaged value 30-sq. inch block.


b b

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Insecticide Residue in Sample Soil

Applied, mg./l

Runoff Water, mg./l.

< 1 » -

Distribution of Insecticides Sprayed by Airplane on an Irrigated Corn

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