Complex simulation models generally provide an accurate assessment of subsurface behavior of contaminants. However, they are limited to situations where adequate data are available. In reality, such data are not available for national and regional scale assessments. Due to these reasons, a GIS-aided screening tool is being used for the islands of Hawaii for a qualitative evaluation of pesticide leaching based on soil and chemical benchmark properties since mid-1990's. In this study, an attempt has been made to update the tool that allows additional agrochemicals, i.e., volatile organic compounds (VOCs), to be assessed. As convective mobility implemented alone as a screening indicator of pesticide leaching is not adequate for substances with high volatile loss, i.e., vapor-phase transport, the current tool is not suitable to screen the leaching behavior of VOCs. To account for loss by volatilization, the previous version of the tool is further expanded to include additional terms such as liquid-vapor partitioning for the retardation factor (RF) and vapor loss at the soil surface for the attenuation factor (AF) estimations, respectively. From the results, it is shown that the leaching potential of selected VOCs is assessed well by the ranking scheme provided by the extended screening tool. In addition, the modified tool is in fairly good agreement with closed-form models that describe VOC leaching potential in soils, as long as leaching is dominant and there is little water to evaporate. Therefore, the simple mobility indices, i.e., RF and AF, extended in this study not only assist decision makers determine priority VOCs responsible for groundwater contamination, but can be still used as a first-tier screening tool on the islands of Hawaii.

Enhancement of a pesticide leaching assessment tool in Hawaii for screening volatile agrochemicals

244th National Meeting (2012)

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