ARS | Publication request: SOLAR RADIATION, RELATIVE HUMIDITY, AND SOIL WATER EFFECTS ON METOLACHLOR VOLATILZATION

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract
Publication Acceptance Date: July 1, 2004
Publication Date: August 22, 2004
Citation: McConnell, L.L., Prueger, J.H., Gish, T.J., McKee, L.G., Hatfield, J.L., Kustas, W.P. 2004. Solar radiation, relative humidity, and soil water effects on metolachlor volatilzation [Abstract]. American Chemical Society 228th National Meeting, August 22-26, 2004, Philadelphia, Pennsylvania, Agrochemicals Division. 67(78):65.

Technical Abstract: Pesticide volatilization is a significant loss pathway that may have a detrimental impact on surrounding environments. This five-year study was designed to evaluate the impact of meteorological variables and surface soil water on volatilization losses of the pre-emergent herbicide, metolachlor. Herbicide vapor concentrations were measured after application using polyurethane foam plugs at five heights above the soil surface. Volatilization fluxes were computed using pesticide concentration profiles with a flux gradient technique using corresponding eddy covariance measurements. The highest flux rates were found during years with wet soil conditions combined with high temperatures and intense solar radiation, especially in 2001 where a maximum flux rate of 1500 ng m-2 s-1 was observed. Cumulative volatilization losses across years varied from 5 to 25% of applied active ingredient, with over 90% of losses occurring the first 72 hours. Results suggest that at conditions >20% soil water content, metolachlor volatilization losses can increase exponentially.