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Title: PREDICTING PESTICIDE VOLATILIZATION FROM BARE SOILS

Author
item Yates, Scott
item Schneider, Sharon
item SPENCER, WILLIAM - USSL, ARS, USDA

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 5/10/2004
Publication Date: 2/10/2005
Citation: Yates, S.R., Papiernik, S.K., Spencer, W.F. 2005. Predicting pesticide volatilization from bare soils. In: Clark, J.M. and Ohkawa, H., editors. Environmental Fate and Safety Management of Agrochemicals. American Chemical Society Symposium Symposium Series: 899. New York, NY:Oxford University Press. p. 101-110.

Interpretive Summary: The occurrence of pesticides in the atmosphere or in water supplies is an important national issue. Numerous monitoring studies have demonstrated that agricultural use of pesticides can contribute to both atmospheric and water contamination. Pesticide movement in the soil zone is affected by many interrelated factors such as the pesticide application methods, soil and environmental conditions, and water management practices. Volatilization is an important route of dissipation for many pesticides. Volatilization reduces the pesticide available to control pests, reduces the potential of ground water contamination, but increases contamination of the atmosphere. This poses a risk to persons living near treated fields since many pesticides are considered to be carcinogenic. To protect public health, there is need for more information on the important processes and mechanisms that affect pesticide fate and transport under typical field conditions. The purpose of this paper was to study the influence of the surface boundary condition on the pattern of pesticide emissions into the atmosphere and to assess the ability to simulate accurate and realistic emission rates. A numerical model was developed to simulate triallate movement in soil, and volatilization into the atmosphere.

Technical Abstract: Understanding the processes and mechanisms that affect pesticide volatilization from fields is important in developing methods to control emissions. Changes in ambient air temperature and atmospheric stability can strongly affect volatilization. A field study was conducted to measure the volatilization rate. A numerical model was developed to simulate pesticide fate, transport and volatilization. Three volatilization boundary conditions were used to assess the accuracy in predicting the volatilization rates. First, a stagnant boundary layer and isothermal conditions are assumed. Second, a temperature-dependent stagnant boundary layer is considered. A third boundary condition that couples soil and atmospheric processes was found to provide an accurate and realistic simulation of the instantaneous volatilization rates compared to the other boundary conditions. For certain information, such as cumulative emissions, all the boundary conditions yielded similar results and suggest that simpler methods may be useful for this information.