Chapter 6
Surface Runoff of Selected Pesticides Applied to Turfgrasses 1
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T. L . Watschke , R. O. Mumma , D. T. Linde , J. A. Borger , and S. A. Harrison 1
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Departments of Agronomy andEntomology,The Pennsylvania State University, University Park, PA 16802 Delaware Valley College, Doylestown, PA 18901 Nittany Geoscience, State College, PA 16802
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The potential for movement of pesticides in surface runoff from golf courses has brought about the need to determine the extent to which certain chemicals are transported by such means in addition to movement below the root zone. This study was conducted in 1992 and 1993 using a herbicide, an insecticide (applied only in 1993), and a fungicide applied at label rates to two turfgrasses maintained as golf course fairway turf. The turf species used were perennial ryegrass (Lolium perenne, L.) and creeping bentgrass (Agrostis stolonifera L . var. palustris (Huds.). Far.; syn. Agrostis palustris Huds.). The herbicide used was mcpp [(2-(2-methyl-4-chlorophenoxy)) proprionoic acid], the insecticide was isazofos (o-(5-chloro-1-(1-methyl-ethyl)-1H1,2,4-triazol-3-yl)-o,o-diethyl phosphorothioate), and the fungicide was triadimefon 1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4triazol-1-yl)-2-butanone). The plots were sloped and irrigated at 152 min h-1 to force runoff within 24 hr of any pesticide application. Collection of runoff consisted of the following, first liter, second liter, and a composite that was collected at a rate of 16 ml min throughout the runoff event. A leachate sample was collected at approximately 15 cm below the surface. In both years, residues of mcpp could be detected in the first two liters of runoff; but within two weeks, the concentration found was reduced by 99.5 percent. In 1993, after the turf was more mature, the concentrations found in first two liters were substantially lower and by the end of three weeks no residue could be -1
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© 2000 American Chemical Society
In Fate and Management of Turfgrass Chemicals; Clark, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
95 detected. Analyses for triadimefon also included the analyses for tridimenol, a metobolite. Residues of both the parent compound and the metabolite were found on all sampling dates in 1992. One day after treatment, residues ranged from 46 to 922 μg L , but within four weeks, concentrations dropped by as much as 80 percent. By six weeks, the concentration of the metabolite exceeded that of the parent and by October the detection of both compounds was below 5 μg L . In 1993 substantially lower concentrations were found (less than 17 μg L for both compounds even in the first liter sampled). After 4 weeks, no residues were found in excess of 4 μg L . Isazofos was applied only in 1993 and residues were found only for samples collected the first day after application. Concentrations of isazofos and tridimefon/ tridimenol in leachate were found to be very similar to the composite runoff samples (both were substantially lower than the concentrations found in the first two liters of runoff). The concentration of mcpp in the leachate was lower than for any other sampling point. These results suggest that certain pesticides applied to sloped plots of turfgrass can be transported in surface runoff when irrigation is applied more heavily than the norm within 24 hr of the pesticide application. Surprisingly, considering the irrigation rate, the level of detection for all compounds was very low even in the first two liters of runoff. Further, the application of pesticides to the turf was made within 15 cm of the weir collector for the runoff water. -1
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The potential transport of pesticides applied to golf courses in surface runoff has been identified as a concern for the environment, particularly in areas where the land surrounding the golf course is ecologically fragile. Limited research has been conducted with regard to determining pesticide transport from turfgrass areas specifically grassed and managed similar to a golf course fairway. The research that has been conducted has focused primarily on nutrient and sediment movement, the characterization of runoff from turf, and the differences in runoff between sodded versus seeded turf (Bennett, 1979; Gross et al., 1990, 1991; Harrison et al., 1993; Morton et al., 1988; Watson, 1985; Linde et al., 1994, 1995). These studies consistently found that the volume of runoff from properly managed turfgrass sites was low (even when excessive irrigation was applied) and that sediment and nutrient transport was also very low (below public drinking water standards). Although previous research has not found significant nutrient transport in runoff, it cannot be assumed that pesticides would follow a similar pattern of movement. Previous research has also consistently found low concentrations of nutrients in leachate with the exception of the downward movement of nitrate from soluble sources applied to sandy soil conditions in conjunction with excessive irrigation. Limited research has been conducted to determine the leaching potential of pesticides applied to turf. Bowman (1990) and Petrovic (1994) measured the downward migration of isazofos in different soil textural types and found that soils comprised of coarser particles allowed for greater migration. The objective of this study was to determine the concentration in runoff and leachate water of three pesticides applied to slopes grassed and maintained like golf course fairways. In Fate and Management of Turfgrass Chemicals; Clark, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
96 Materials and Methods This experiment was conducted at the turfgrass runoff facility located at The Pennsylvania State University's Landscape Management Research Center on the University Park campus. These facilities have been characterized by Harrison et al. (1993) and more recently by Linde et al. (1995) which included the general maintenance practices that were used on these plots. Water Collection Procedures. Water samples were collected from several runoff events, which were forced by irrigation at a rate of 152 mm hr" . The initial runoff event was typically within 24 hr of the pesticide application. The duration of irrigation varied due to environmental conditions and species being irrigated (runoff occurred more quickly and at greater volumes from perennial ryegrass than from creeping bentgrass). The difference in runoff between perennial ryegrass and creeping bentgrass has been reported and characterized by Linde et al. (1995). The sampling program used was as follows; runoff, first liter (#1), runoff, second liter (#11), runoff, composite 16 ml min' (#111), and a leachate composite that was collected from the sample collector at the conclusion of the irrigation event. The leachate sample was a composite from subsurface sample collection devices in four locations/plot. The timing of the various pesticide applications and the subsequent irrigation events can be found in Tables I and II.
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Table I. Treatment schedule and watering/sampling events of turfgrass test plots in 1992. Date
Treatment Chemical
Rate Lha
Date
0.78 1.44 1.04 1.04
June 10 June 24 July 15 Aug 19 Sept 9 Oct 14
Watering Type
Samples
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May 5 June 9 June 23 July 14 Aug 18 Sept 8 Oct 6
Fertilizer Mecoprop Trichlorfon Triadimefon Triadimefon Fertilizer Fertilizer
Irrigation Irrigation Irrigation Irrigation Irrigation Irrigation
28 28 28 28 28 28
Pesticide Application Procedures. A l l pesticides were applied at label recommended rates using a conventional boom-type sprayer calibrated to deliver a volume of 30.4 g ha (Tables I and II). Each of the six slopes was entirely treated with the exception of a 15-cm band located directly adjacent to the weir. This 15-cm band was not treated to insure that drift from the treatment being applied would not come in direct contact with the weir, thus bypassing foliar interception by the turf. 4
In Fate and Management of Turfgrass Chemicals; Clark, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
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Table Π. Treatment schedule and watering/sampling events of turfgrass test plots in 1993.
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Date May 11 May 25 June 8 June 29 Aug 17 Sept 7 Sept 20 Oct 5
Treatment Chemical Dithiopyr Fertilizer Mecoprop Isazofos Triadimefon Fertilizer Trichlorfon Fertilizer
Rate
Date
0.78 0.78 1.04
June 9 June 30 Aug 18 Sept 8 Sept 21 Oct 6
1.96
Watering Type
Irrigation Irrigation Irrigation Irrigation Irrigation Irrigation
Samples
28 28 28 28 28 28
Pesticide Analysis of Water Samples. Mecoprop. Solid Phase Extraction. Sample preparation for HPLC analysis was done using Baker High Capacity (HC) CI8 solid phase extraction (SPE) cartridge (J.T. Baker; Phillipsburg, NJ). The cartridge was attached to a Visiprep 12 port SPE Vacuum Manifold (Model 5-7030; Supelco Inc., Bellefonte, PA) via the outlet end. A 75-mL polypropylene reservoir was inserted onto the inlet end of the SPE column. The SPE was conditioned by adding approximately 18 mL of methanol to the reservoir and letting the methanol percolate through the SPE by gravity until droplets formed at the manifold outlet. Then, a draw of 101 mm of mercury was applied to remove almost all the methanol before 10 mL of distiiled-deionized water was added to the reservoir and drawn through with vacuum as above to almost dry. The sample was then added to the reservoir and a vacuum of 254 mm of mercury was applied and the flow rate through the individual sample SPE tube was adjusted to approximately 6-8 mL per minute. The water was prepared for extraction by measuring out up to 200 mL of field sample that had been thoroughly mixed by shaking into an appropriate sized beaker and acidified to pH of 2.5-2.8 with trifluoroacetic acid (TFA). The sample water was then filtered through Whatman GF/F glass membrane filters (0.7 mm pore size) and added to the SPE column reservoirs. The vacuum was set at 178-254 mm of mercury and flow adjusted to 5-8 ml min" . After all the sample was eluted through the SPE, the SPE was rinsed with an additional 10 mL of distiiled-deionized water. The SPE then was dried with a vacuum draw of 432 mm of mercury for 30 minutes. Additional clean up was performed by adding 4 X 500 μL of acetonitrile: water (50:50 v/v) with the pH adjusted to
