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| Web URL(s): | http://archive.lib.msu.edu/tic/rpr/1998/61859,%20U%20Maryland,%20Carroll.PDF
Last checked: 10/22/2013
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| Publication Type:
| Report |
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| Material Type: | Manuscript |
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| Monographic Author(s): | Carroll, Mark J.; Hill, Robert L.; Herner, Albert |
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| Author Affiliation: | Carroll and Hill: Principal Investigator, Department of Agronomy, University of Maryland; and Herner: Cooperator, Environmental Chemistry Laboratory, USDA: Beltsville |
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| Monograph Title: | Modeling Pesticide Transport in Turfgrass Thatch and Foliage: [1998 Annual Research Report], 1998. |
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| Publishing Information: | [College Park, Maryland]: University of Maryland |
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| # of Pages: | 14 |
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| Collation: | [14] pp. |
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| Abstract/Contents: | "Pesticides applied to mature turf move into the soil after being washed off foliage and moving through Turfgrass thatch. Any attempt to predict the movement of pesticides applied to turf requires that the retention characteristics of the pesticide to foliage and thatch be known. In 1997 and 1998 a series of sorption and transport studies were conducted to characterize the movement of carbaryl in soils containing a surface layer of Turfgrass thatch. The sorption studies were conducted using a device called a mechanical vacuum extractor. This device precisely controls the rate at which a solution moves through a column of porous media. The adsorption and desorption properties of a 3.5 year old, 2.3 cm thick Southshore creeping bentgrass thatch, and a 6 year old, 3.4 cm thick Meyer zoysiagrass thatch were compared with the soil residing below each thatch layer. The adsorption kinetics of carbaryl to thatch and soil were similar. Sorption equilibrium was achieved within 4 hours in all media. Both Turfgrass species thatch had much higher carbaryl adsorption capacities than the underlying soil. There was, however, no difference in the adsorptive capacities of the two Turfgrass species thatch. The normalized sorption coefficients of the four media were similar suggesting that differences in the carbaryl sorptive capacities of thatch and soil were solely due to differences in the organic carbon content of the media. Desorption losses were evaluated by subjecting columns of thatch or soil to three suggestive leaching events. The leaching events took place after allowing carbaryl to adsorb to the thatch or soil for 24 hours. The amount of carbaryl detected in the leachate was used to determine the proportion of carbaryl that was desorbed from the sample. Carbaryl retention in soil was much lower than in thatch during the first leaching event. By the end of the third leaching event there was little difference in the proportion of carbaryl retained in the bentgrass thatch and soil. In contrast, zoysiagrass thatch always retained a greater proportion of carbaryl than the underlying soil. This suggests that carbaryl is more tightly bound to zoysiagrass thatch than to the underlying soil. Undisturbed columns of soil or soil plus a surface layer of thatch were used to determine the effect of thatch on the carbaryl transport in soil. Columns having a surface layer of zoysiagrass thatch were more effective in reducing carbaryl transport than columns having a surface layer of creeping bentgrass thatch. Visual examination of the bentgrass site columns revealed extensive earthworm burrowing. The channels present in these columns likely reduced the effectiveness of bentgrass thatch to inhibit carbaryl transport. Bromide and carbaryl breakthrough curves obtained from the transport study were used to evaluate the performance of the linear equilibrium (LEM) and the two-site non-equilibrium (2SNE) models to predict carbaryl transport. The latter model uses a non-equilibrium form of the convective-dispersion equation to predict solute movement in porous media while the former uses a linear equilibrium form of the equation to predict solute movement. The carbaryl breakthrough curve (BTC) data were also used to compare the use of column retardation factors (R) based on our laboratory measured thatch and soil sorption coefficients with model fitted R's to predict carbaryl transport. Modeling of bromide transport presented strong evidence of significant two domain flow in all columns except the zoysiagrass site soil columns. In columns exhibiting two domain flow use of retardation factors based on laboratory measured adsorption coefficients accounted for 74 to 94% of the variability in carbaryl transport. Slightly improved estimates of carbaryl transport were obtained when R was kept as a fitting parameter. In Columbus where two domain flow was not apparent, the LEM model could satisfactorily describe carbaryl transport only when R was curve-fitted. Use of R's based on laboratory derived adsorption coefficients resulted in poor LEM estimates of carbaryl transport. The 2SNE model gave reasonable estimates of carbaryl transport when R was calculated using the adsorption coefficients we determined in our sorption studies. Goals: To quantify the washoff of pesticides from bentgrass foliage as a function of time after application and pesticide formulation.; To determine the effect of solution residence time on the sorption of pesticides to turfgrass thatch.; To compare the use of linear equilibrium, two-site non-equilibrium and one-site kinetic non-equilibrium forms of convection/dispersion equation to predict pesticide transport through turf containing a surface layer of thatch." |
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| Language: | English |
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| References: | 4 |
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| See Also: | See also related summary article "Development of a layered model to predict pesticide transport in turfgrass thatch" 1998 Turfgrass and Environmental Research Summary [USGA], 1998, p. 54-55, R=61859. R=61859 |
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| Note: | Also appears as pp. 632-646 in the USGA Turfgrass Research Committee Reporting Binders for 1998.
"1998 Annual Report presented to the United States Golf Association Green Section Research"
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