Conclusion
The study generally supports the contention that much of the hazardous trace material in coals may be removed by fine grinding and agglomeration prior to firing. In addition to reducing this source of heavy metal discharge to the environment, this type of processing has a number of advantages over conventional operation. The cost and difficulty in disposing of large amounts of ash in the urban environment are avoided. Hidden costs due to the ash, such as reduced boiler capacity, wear on tubing and maintenance of the collection and ash-handling system are also reduced. Ash in the form of tailings can be handled more economically at the mine site and needless ash transportation to the power plant does not take place. Even marginal coals can be pelletized to a low-ash product which is readily handled and dust-free. In addition, there is the possibility of recovering appreciable amounts of metals with commercial value. In this study, tailings quite high in levels of copper, iron, lead, manganese, and zinc were produced. Although the metal content of the tailings may be below the amount ordinarily required for economic recovery, these low levels may justify recovery because of the proportion of mining and treating costs borne by the coal beneficiation operation. It must not be assumed that these metals could be recovered equally well from fly ash after firing since high-temperature complexes (e.g., spinels), difficult to recover and separate, may be produced. As was noted, low-temperature processing has the added advantage of removing for possible subsequent recovery materials which may be volatilized and not trapped in fly ash. Regarding the environmental impact of the oils used in agglomeration, checks have indicated that they are effectively adsorbed quantitatively by the fine, high-surface
area coal particles. Any traces of oil remaining in the tailings fraction could be reused by recycling the water after solids removal. Volatile components of the oil evaporated during thermal drying could be condensed from the dryer exit gases and reused if they constituted an air pollution problem. Oils of low volatility would remain in the agglomerates and increase the fuel value of the product. Acknowledgments
The authors thank I. E. Puddington for his continuing interest and suggestions, and E . C. Goodhue, A. Mykytiuk, and P. Tymchuk for their help in the chemical analyses. L i t e r a t u r e Cited Abernathy, R. F., Hattman, E . A,, L‘.S. Bur. Mines, Rep. Inuest. 7452 (November 1970). Billings, C. E., Matson W. R., Science, 176, 1232 (1972). Brown, R., Jacobs, M. L., Taylor, H. E., Amer. Lab. 29 (November 1972). Capes, C. E., McIlhinney, A. E., Coleman, R. D., Trans. AIME., 274,233 (1970). Capes, C. E., McIlhinney, A. E. Sirianni, A. F., Puddington, LE., Proc. 12th Bien. Conf., Inst. Briquet. Agglom., 53 (1971). Capes, C. E., Sutherland, J. P., Ind. Eng. Chem. Process Des. Deuelop., 5 , 330 (1966). Farnand, J . R., Puddington, I. E., Can. Mining Met. Bull., 62, 267 (1969). Rains, T. C., Nut. Bur. Stand., Washington, D.C., private communication (1971). Ruch, R. R., Gluskoter, H. J., Kennedy, E . J., Enuiron. Geol. Notes (Illinois State Geological Survey), No. 43, p 1 (February 1971). Sirianni, A. F., Capes, C. E . , Puddington, I. E., Can. J. C h e m Eng., 47, 166 (1969).
Received for reuieu February I , 1973. Accepted September 5, 1973. NRCC AJo. 13,518.
Atrazine, Propachlor, and Diazinon Residues on Small Agricultural Watersheds Runoff Losses, Persistence, and Movement William F. Ritter,’ Howard P. Johnson, Walter G. Lovely,2 and Myron Molnau3 Agricultural Engineering Department, Iowa State University, Ames, Iowa 5001 0
In the past 10 years, many research workers have meaAtrazine (2-chloro-4-ethylamino-6-isopropylamino-s-sured the concentrations of organochlorine insecticides in triazine), propachlor (2-chloro-N-isopropylacetanilide), rivers. Only a few investigators have presented data for and diazinon (0,O-diethyl 0-(2-isopropyl-6-methyl-4-py- pesticide residues in surface runoff and sediment. White rimidinyl) phosphorothioate) losses in sediment and suret al. (1967) measured atrazine losses in water and sediface runoff were measured from four watersheds ranging ment from fallow plots of Cecil sandy loam soil (6.5% in size from 1.9-3.8 acres and located in the loessial soil slope). They found, using a rainfall simulator, that a 1-hr region of western Iowa. Two of the watersheds were plantstorm of 2.5 in. occurring 96 hr after atrazine was applied ed to ridged corn, and two were planted to surface-cona t 3 lb/A, resulted in atrazine losses of 18%. Most of the toured corn. Movement of atrazine, propachlor, and diazatrazine losses were associated with the water fraction beinon in the soil profile and degradation of these pesticides cause of the greater amounts of water lost. Car0 and Taywere measured. Pesticide losses were much greater from lor (1971) found that dieldrin losses in sediment and in the surface-contoured watersheds than the ridged waterrunoff water reached 2.2 and 0.0770,respectively, of the 5 shed. Significant amounts of surface-applied atrazine and propachlor were removed from the surface-contoured watersheds by storms occurring shortly after the pesticides were applied. Insignificant amounts of diazinon were rePresent address, Agricultural Engineering Department, University of Delaware, Xewark, Del. 19711. To whom corresponmoved in the surface runoff and sediment. Generally, pesdence should be addressed. ticide concentrations were higher in the sediment than in * Present address, ARS-USDA, Agricultural Engineering Dethe runoff water; however, greater total losses were associpartment, Iowa State University, Ames, Iowa 50010 Present address, Agricultural Engineering Department, Uniated with the greater volume of water. versity of Idaho, Moscow, Idaho 83843
38
Environmental Science &. Technology
of 50% H20 and 50% HzS04 were added to 80 ml of the extract, and the mixture was shaken every 15 min for a 2-hr period. After 2 hr, 9 ml of distilled water were added, and the mixture was shaken for 30 sec. After the two layers separated, the chloroform layer was drawn off and discarded; 25 ml of ethyl ether were added to the aqueous layer, and the mixture was shaken for 30 sec. The aqueous layer was drawn off and frozen until an aliquot was analyzed on a Beckman uv spectrophotometer. The detection Experimental Procedure limit for the soil samples was 0.2 ppm and, for the water samples, 0.02 ppm. The major disadvantages of the uv The study was conducted on small agricultural watermethod are that it is subject to various interfeiences and sheds near the Western Iowa Experimental Farm, Castadoes not distinguish between atrazine and its degradation na, Iowa. These watersheds ranged in size from 1.3-3.8 product, hydroxyatrazine. Today s-triazines are analyzed acres and had slopes of 10-1570. Three soil types predominated on each watershed; Ida silt loam, Monona silt loam, by gas-liquid chromatography with either a microcoulometric detector or electrolytic conductivity detector (Horand Napier silt loam. In 1967, four watersheds were plantmann et al., 1972). The glc method is faster and more aced to surface-contoured corn, and a t the first cultivation, curate than the uv method. ridges were established on two of the watersheds. From 1968-70, two of the watersheds were planted to ridged Propachlor was extracted from the 15- to 30-gram soil corn, and the other two watersheds were planted to sursamples with 30-60 ml of acetonitrile for 15 min on a meface-contoured corn. In 1967 and 1968, propachlor (2chanical shaker (Ritter, 1971). After the soil-solvent mixture was filtered, a 3- or 4-pl. aliquot was injected into a chloro-N-isopropylacetanilide) was sprayed as a wettable powder formulation a t 4 lb/A a t planting to a ridged and gas chromatograph. Propachlor water samples (200 ml) to a contoured watershed, and atrazine (2-chloro-4were extracted three times in a separatory funnel with ethylamino-6-isopropylamino- s-triazine was sprayed as 25-ml portions of benzene. The solvent was combined a wettable powder formulation a t 2 lb/A to the other two from each extraction; a 3- to 4-pl. aliquot was injected watersheds. In 1969 and 1970, the rates for propachlor and into a gas chromatograph. Minimum detection limits for propachlor soil and water samples were 0.2 and 0.02 ppm, atrazine were changed to 6 lb/A and 3 lb/A, respectively. Diazinon [ 0,O-diethyl 0-(2-isopropyl-4-methyl-6-pyrimi- respectively. dinyl) phosphorothioate] was applied in a granular formuDiazinon was extracted from 30-gram soil samples with 60 ml of acetonitrile on a mechanical shaker for 30 min lation to the four watersheds in a band application 1-2 in. (Ritter, 1971). After the soil-solvent mixture was filtered, deep a t a rate of 1 lb/A each year a t the first cultivation. a 3- to 4-pl. aliquot was injected into a gas chromatoWater and sediment samples were obtained from the graph. Diazinon water samples (300 ml) were extracted four watersheds with single-stage sediment samplers. with two 90-sec shakings in a separatory funnel by use of Some additional samples were collected from two of the 50 ml of hexane for each shaking. The solvents from each watersheds with 2-ft-diameter Cochocton runoff samplers extraction were combined and then concentrated to a final (Parsons, 1954). All the water and sediment samples were volume of 10 ml on a hot water bath or injected directly collected in glass bottles and transferred to polyethylene ( a 3- to 4-pl. aliquot) into a gas chromatograph. Minimum bottles to be frozen immediately after collection. detection limits for diazinon in soil and water samples Soil samples were taken with a 3/4-in.-diameter soilwere 0.1 and 0.01 ppm, respectively. sampling probe. Samples were collected within 24 hr after A %-in. X 6-ft glass column packed with a 5% Carbothe pesticides were applied and a t seven-day intervals for wax 20M liquid support on 60/80 Chromosorb W was used the first few weeks after application. Soil samples for defor analysis of the diazinon and propachlor samples. Opertermination of atrazine content were taken throughout the ating conditions for the MicroTek 220 gas chromatograph growing season; soil samples for determination of diazinon with an Ni-63 electron capture detector were: injection and propachlor content were collected for four to six port temperature 270 -280°C, detector temperature 275weeks after application. Seven individual soil cores were 300°C, and column temperature 190°C. Nitrogen was used taken normal to the corn row and composited. Points as a carrier gas with flow rates of 80-100 ml/min. for taking soil samples were located on the watershed by laying out a 125 X 125-ft grid system on each watershed. All soil samples analyzed for atrazine, propachlor, and This grid system pattern resulted in having five and 12 diazinon were extracted a t the soil moisture content a t sampling sites on the surface-contoured and ridged waterwhich they were collected. At the time of analysis, a porsheds where atrazine was applied, and seven and six samtion of the soil sample (10 grams) was used for a moisture pling sites on the surface-contoured and ridged watersheds determination. Soil moisture samples were dried at 105°C where propachlor was applied. In 1967, the 0-4- and 4-8for 24 hr. All data were corrected for soil moisture conin. depth of sampling did not give a clear picture of pestitent. cide movement in the soil profile. The sample depths used The average extraction efficiencies of soil samples fortiin 1968-70 were 0-1, 1-3, and 3-5 in., for the first few fied with propachlor, atrazine, and diazinon were 9C, 85, samplings, and 0-2, 2-4, and 4-6 in. for midseason samand 63%. These values were based on 10 or more samples plings. Late-fall samples were taken at depths of 6-8 and fortified with pesticide a t different soil moisture contents. 8-10 in. All soil samples were frozen immediately after The extraction efficiencies varied with soil moisture conthey were taken. tent, so the data collected in the field were not corrected The ultraviolet method described by Geigy Chemical for extraction efficiency. Corp. (1965) was used t o analyze the soil, water, and sediExtraction efficiencies for the soil samples were within ment samples for atrazine. Chloroform was used to extract the state-of-the-art for the technique used. Hormann et the atrazine from the soil and water samples. Atrazine al. (1972) reported extraction efficiencies of 70-80% for was extracted from the 40-gram soil samples with 120 ml atrazine soil samples. of chloroform for 30 min on a mechanical shaker. The pesExtraction efficiencies for water samples fortified with ticide was extracted twice from a 200-ml sample of water propachlor, atrazine, and diazinon were 97, 107, and 78%. with 50-ml portions of chloroform. After extraction, 1 ml These average extraction efficiencies were based on three
lb/A application. Greatest losses of dieldrin in the runoff water occurred during the first two weeks after applications. The objective of this study was to measure pesticides in surface runoff and sediment from agricultural watersheds and to measure the movement and concentration of these pesticides in the soil profile with time.
Volume 8, Number 1 , January 1974
39
Table I. Amounts of Atrazine in Water and Sediment from Surface-Contoured and Ridged Watersheds Amount of runoff, in. D a t e of storm
No. days a f t e r application
6-11-69 6-22-69 6-28-69 7-7-69 8-6-69 8-8-69 5.13-70 5-30-70 6-11-70
34 45 51 60 90 92 7 24 36
Amount i n water, Ib/A
_ _ _ _ _ _ ~
Ridged
Surfacecontoured
Ridged
Surfacecontoured
0.29 0.06 0.23 0.35 0.40 0.30 0.58 0.28 0.06
0.51 0.04 0.39 0.59 0.73 0.42 0.16 0.11 0.24
0.056 0 * 002 0.006 0.009 0.001 0.001 0.061 0.009 0.005
0.087 0.002 0.012 0.019 0.003 0.002 0.339 0.020 0.008
I
,
,
Amount i n sediment, Ib/A Surfacecontoured
Ridged
0.001 TU
0.019
b
0.005 0.001
0.014 0.003 0.001 0.000 0.109 0.001
b
T
T
b b
b
a Trace. b No data collected.
Table II. Total Amounts of Propachlor in Water and Sediment for Surface-Contoured Watershed, 1970 D a t e of storm
Days since appliAmount of cation runoff, in.
a
5-13-70 5-30-70 6-11-70
Total loss i n water, Ib/A
Total loss in sediment, I b/A
0.116 0.017 0.014
0.039 0.000 0.000
0.40 0.26 0.24
25 37
determinations for propachlor and diazinon and on 13 determinations for atrazine.
Results and Discussion Runoff and Sediment. The total amounts of pesticide in the runoff water were calculated from pesticide concentrations detected in the water samples and from the runoff data. Sediment-loss calculations were based on sediment collected in the single-stage samplers. Sediment concentrations were obtained from the single-stage samplers for the rising side of the runoff hydrograph. No samples were collected on the falling side. Sediment concentrations for the falling side were estimated from sediment relationships reported by Doty and Carter (1964), Dragoun and Miller (1964), and personnel of the United States Department of Agriculture (1970). The results, as shown in Table I, indicated that storm runoff, occurring shortly after the atrazine was applied, carried significant amounts of atrazine in the water and sediment. For a storm that occurred on May 13, 1970, seven days after the atrazine was applied, approximately 0.488 lb/A or 15% of the total amount of atrazine applied
to the surface-contoured watershed was in the surface runoff and sediment. Concentrations of atrazine in the water ranged from 4.91-1.17 ppm and from 7.35-1.77 ppm in the sediment. For the same storm. 0.066 lb/A of atrazine was in the water and sediment from the ridged watershed. In general, the amount of atrazine in the water and sediment decreased with time after application. For storms occurring two months after application, the amounts of atrazine in the water and sediment were insignificant. Approximately 0.48 lb/A or 16% of the total amount of atrazine applied to the surface-contoured watershed was in the surface runoff and sediment in 1970. Of this amount, 0.37 lb/A was in the surface runoff, and 0.11 lb/A was attached to the sediment. In 1969, 0.13 lb/A was in the surface runoff, and 0.04 lb/A was attached to the sediment from the surface-contoured watershed. Water and sediment samples were collected and analyzed for propachlor in 1967 and 1970. No runoff occurred in 1968 and 1969 before the propachlor had degraded. No detectable amounts of propachlor were in water and sediment samples in 1967. The first samples were collected 14 days after the propachlor was applied, and the last samples were collected 25 days after the propachlor was applied. Table I1 shows the amount of propachlor in the runoff and sediment from the surface-contoured watershed in 1970. No runoff occurred on the ridged watershed in 1970 before the propachlor evidently had degraded. After a storm on May 13, 1970, 0.155 lb/A of propachlor was in the runoff water and sediment from the surface-contoured watershed. In 1968 and 1969, 66 water samples and 18 sediment
Table Ill. Concentration of Propachlor in Soil for Ridged Watershed, 1969 D a t e of sampling
May May
May
May
a
40
7 14
20
28
Days from application
Location Depth, In.
1
0-1
4.14 0.00 3.19
1-3 3-5
T T
14
0-1
22
1-3 3-5 0-1 1-3 3-5
1.08 0.00 0.00 2.31 0.00 0.00
1
8
0-1 1-3
Trace.
Environmental Science & Technology
2
3 4 Concentration, p p m
Extremes
5
6
4.37
2.64
2.33
8.59
6.73
Ta
T
0.00
0.00
a.oo
3.56 0.00
3.11 0.00
0.64
3.82
0.00
0.00
1.16 2.38
2.76 0.00 0.00 0.00 0.00 0.00
2.04 0.93
1.73 0.49
0.61 0.00
0.38 0.00
6.47 0.00 0.00 3.52 0.00 0.00 1.27 0.82
4.29 1.99
0.00
Av.
4.86 0.00 3.47 0.00 0.00 2.05 0.63 0.00 1.48 0.47 0.00
Max
8.59 T
6.47 T T
3.52 2.38 0.00 4.29 1.99 0.00
Min
2.33 0.00 0.64 0.00 0.00 1.08 0.00 0.00 0.38 0.00 0.00
Table IV. Average Concentration of Atrazine in Soil Profile for Ridged Watershed, 1969 and 1970 Days f r o m ap .D . lication
0
6
13
20
32
3.30 0.67
1.86 0.39
2.48 0.88 0.55
2.67 0.63 0.22
2.05 1.02 0.29
Depth, in.
0-1 1-3 3-5 0-2 2-4 4-6 6-8
45 62 Concentration, p p m
1.74 0.63 0.17
1.35 0.64 0.37
78
99
140
178
1.15 0.60 0.29 0.16
0.83 0.54 0.36 0.25
0.72 0.65 0.46 0.40
0.35 0.39 0.39 0.32
Table V. Average Concentration of Atrazine in Soil Profile for Surface-Contoured Watershed, 1969 and 1970 Days f r o m application Depth, in.
0-1 1-3 3-5 0-2 2-4 4-6 6-8
45 62 Concentration, p p m
0
6
13
20
32
5.87 1.05
3.09 0.40
4.07 1.07 0.42
4.50 1.36 0.55
1.92 1.32 0.38
samples were analyzed for diazinon. Detectable concentrations of diazinon were in 19 of the water samples, with a maximum concentration of 82 ppb. Eight of the sediment samples contained diazinon, with a maximum concentration of 0.17 ppm. Only one water sample collected from the ridged watershed contained diazinon. The highest concentrations of diazinon were in the runoff and sediment samples collected 4-10 days after diazinon was applied, with a maximum of 0.1% of the diazinon in the surface runoff and sediment from one of the surface-contoured watersheds for a storm that occurred four days after the diazinon was applied. The low concentrations of diazinon in the water and sediment were due in part to the rapid degradation and in part to incorporation of chemical into the soil. No severe storms occurred during the two years samples were analyzed for diazinon. It is possible that a severe storm might have caused greater losses of a chemical incorporated 1-2 in. than the data indicate. All of the ridges were laid out on the contour, whereas in a typical field situation they may be laid out across the slope. Runoff and sediment losses probably would have been larger if the ridges were not laid out on the contour, but they would have been small compared to conventional tillage systems because of the trash left on the surface. Soil Samples. The atrazine and propachlor soil-sample concentrations varied greatly a t each sample location with time. Table I11 shows the variation in concentration with time for propachlor for each sample point on the ridged watershed for 1969. Each sample point is a composite of seven individual soil cores taken normal to the corn row. The variation in concentration was similar for atrazine and propachlor soil samples on the other watersheds. The scatter of results in Table I11 is similar to the sample variability experienced by other researchers when measuring pesticide contents under field conditions (Taylor et al., 1971). It is difficult to apply pesticides uniformly on a field scale basis. The chemical should be applied within a few hours to avoid variations in wind velocity. Other factors such as oscillation of the sprayer booms, steep slopes, height of ridges, and variation in tractor operation also influence the chemical application. Increased confidence in
2.26 1.00 0.52
78
2.22 1.01 0.54
1.46 0.83 0.51 0.57
99
140
178
1.45 0.68 0.53 0.25
0.79 1.21 0.75 0.50
0.55 0.71 0.57 0.41
Table VI. Average Carryover of Atrazine in Soil Profile for 1969 and 1970 Days since application
196g4 348
1970b 363
Concentration, p p m Total amount, m g / m $ D e p t h of sam,pling, S u r f a c e Surfacein. contoured Ridged contoured Ridged
0-2 2-4 4-5 6-8 0-2 2-4 4-5 6-8 8-10
0.28 0.19 0.23 0.20 0.56 0.20 0.19 0.33 0.00
0.20 0.34 0.38 0.34 0.34 0.48 0.33 0.34 0.25
21.0 14.3 17.3 14.9 42.0 15.0 14.3 24.7 0.0
14.9 25.5 27.8 25.5 25.5 36.1 24.7 25.5 18.8
a T o t a l a m o u n t s d e t e c t e d in t h e t o p 4 i n . of profile i n 1968 a t t i m e of a p p l i c a t i o n were 490'and 595 mg/m2 f o r t h e s u r f a c e - c o n t o u r e d a n d r i d g e d w a t e r s h e d s , respectively. b T o t a l a m o u n t s d e t e c t e d i n t h e t o p 4 i n . o f profile i n 1969 a t t i m e of a p p l i c a t i o n were 430 a n d 350 rngJm2 for t h e s u r f a c e - c o n t o u r e d a n d r i d g e d w a t e r s h e d s , respectively.
the average pesticide concentration could be obtained if more samples were taken. The accuracy gained by taking more samples has to be balanced against the cost of analyzing the extra samples. Taylor et al. (1971) predicted that, to reduce the coefficient of variation in half in sampling dieldrin, the number of soil cores taken would have to be increased from 8-30/100 m2. Tables IV and V show the average concentration of atrazine in the soil profile for 1969 and 1970 for the ridged and surface-contoured watersheds. Both tables show a general downward trend in concentration. Atrazine moved slowly in the soil profile. Samples'taken 6-8 in. below the surface 80-90 days after the atrazine was applied contained small amounts of atrazine. In 1969, soil samples taken a t the 8- to 10-in. depth in November had average concentrations of atrazine of 0.19 ppm on the ridged watershed and 0.22 ppm on the surface-contoured watershed. There was no detectable difference in the rate of movement or concentration reduction on the two watersheds. Table VI shows small amounts of atrazine carryover in the top 10 in. of the soil profile for samples taken in 1969 and 1970. The average concentrations ranged from 0-0.56 ppm. There was very little difference in the amount of Volume 8, Number 1 , January 1974
41
Table VII. Average Concentration of Propachlor in Soil Profile for Ridged Watershed, 1969 and 1970 Days f r o m application Depth, in.
0-1 1-3 3-5
0
7 Concentration,
4.92 0.31
3.78 0.00 0.00
14 ppm
2.40 0.44 0.00
21
1.37 0.26 0.00
Table VIII. Average Concentration of Propachlor in Soil Profile for Surface-Contoured Watershed, 1969 and 1970 Days f r o m application Depth, in.
0-1 1-3 3-5
0
11.92 0.65
7
14. 21 Concentration, p p m
7.16 0.07 0.00
6.01 1.63 0.17
3.29 0.48 0.00
28
2.43 0.27 0.04
1.0 ppm. After 21 days, no detectable amounts of diazinon were present. Diazinon degrades rapidly in the soil (Ritter et al., 1973). Laboratory tests, conducted a t 43°C and 23% moisture, showed that only 20% of the diazinon was recovered after three days from soil samples treated with 10 ppm diazinon.
Conclusions Ridge planting of corn greatly reduced pesticide losses in the water and sediment when compared to surface-contoured planting. No significant amounts of diazinon were found in the surface runoff and sediment when applied a t the recommended rates and incorporated into the soil. Atrazine moved slowly in the soil profile; small concentrations were detected a t depths of 8-10 in. one year after application a t recommended rates. Only small concentrations of propachlor remained in the soil profile three to four weeks after application. Only traces of propachlor were found a t depths of 3-5 in. Acknowledgment
atrazine carryover between surface-contoured and ridged watersheds. Very little propachlor moved below the 3-in. depth. Tables VI1 and VI11 show the average concentration of propachlor in the soil profile for 1969 and 1970 from the ridged and surface-contoured watersheds. Only 29% and 30% of the propachlor remained in the soil profile on the ridged and surface-contoured watersheds, respectively, after 21 days. Propachlor does not move as far in the soil profile as atrazine because it degrades rapidly under most field conditions. There was a marked difference in the initial concentration of propachlor and atrazine on the ridged and surfacecontoured watersheds although the application rates were intended to be the same. Some of the pesticide landed and remained on the trash on the ridged watersheds. While the trash helps reduce the loss of water and sediment, it intercepts a portion of the chemical before it hits the soil surface. Although the geometry of the ridges and the location of the sprayer nozzles could account for some of the concentration differences between the watersheds, it appears the trash on the ridged watersheds would account for most of the difference in the initial concentration of atrazine and propachlor. Further studies on the effect of trash on pesticide interception need to be made. Only small concentrations were detected in the soil samples analyzed for diazinon. Samples collected a few hours after the diazinon was applied contained less than
42
Environmental Science & Technology
The authors thank the Geigy Chemical Co., Ardsley,
N.Y., for supplying the atrazine and diazinon standards and the Monsanto Chemical Co., St. Louis, Mo., for supplying the propachlor standards. Literature Cited Caro, J. H., Taylor, A. W., J . Agr. Food Chem., 19,379-84 (1971). Doty, C. W., Carter, C. E., ASAE Meeting, Fort Collins, Colo., June 1964. Dragoun, F. J., Miller, C. R., ibid. Geigy Chemical Corporation, Tech. Bull. 7, Ardsley, N.Y., Agricultural Analytical Chemistry, Analytical Dept., Geigy Chemical Corp., 1965. Hormann, W. D., Formica, G., Ramsteiner, K., Eberle, D. O., J. Ass. Offic. Anal. Chem., 55, 1031-8 (1972). Parsons, D. A., U.S. Dept. Agric., SCS TP-124, 1954. Ritter, W. F., P h D thesis, Iowa State University, Ames, Iowa, 1971. Ritter, W. F.. Johnson, H. P., Lovely, W. G., Weed Sei., 21 ( 5 ) , 381-4 (1973). Taylor, A. W., Freeman, H . P., Edwards, W , M . , J. Agr. Food Chern., 19,832-6 (1971). U.S.Deuartment of Agriculture. Columbia, Mo., North Central Watershed Research-Center, Corn Belt Branch, SWC, ARS, USDA, Ann. Res. Rept., 1970. White. A. W.. Barnett. A. P.. Wright. B. G.. Holladav. J. H.. Enviroh. sei. Techno/.,'1, 740-4 (1987);
Received for revieu, August 28, 1972. Accepted September 11, 1973. Joznt Contribution: Journal Paper N o . J-7284 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, and ARS-CrSDA. Projects LVOS. 1815 and 1853.
