Correlation Techniques for Estimating Pesticide Volatilization Flux and Downwind Concentrations

Abstract

Because of growing concerns over the potential risks from exposure to airborne pesticides that have acute and chronic human and ecological health impacts, information on concentrations in air downwind of emission sources is being increasingly required, especially in populated areas. A simple and cost-effective approach to estimating downwind air concentrations from emissions was developed by relating physicochemical properties of various pesticides and other organics with their published volatilization rates (flux) from treated soil, plant foliage, and water. The resulting set of ln−ln correlations was used to estimate flux for pesticides with known physicochemical properties. These estimated flux values were used as source strengths in the EPA's SCREEN-2 dispersion model to calculate downwind concentrations near treated fields for time periods soon after application. Using estimated flux values for carbofuran, oxydemeton-methyl, methidathion, azinphos-methyl, and molinate, downwind concentrations were calculated that compared well with concentrations measured near treated fields for these pesticides applied to field crops, orchards, and rice fields. This approach is useful for prioritizing pesticides that pose potential health hazards and for which monitoring should be considered.