Evaluation of PRZM Volatilization Algorithm for Soil Pesticide Applications.

The US Environmental Protection Agency’s Office of Pesticide Programs currently uses the Surface Water Concentration Calculator (SWCC) to estimate aquatic and drinking water exposure from pesticide applications.  In this presentation, the volatilization algorithm in the Pesticide Root Zone Model (PRZM5) component of the SWCC, inherited from prior PRZM versions, is evaluated for bare soil pesticide applications.  This dissipation route provides additional refinement to water body exposure estimates, accounting for the loss of pesticide due to volatilization from soil, which ultimately lessens the residual pesticide available for runoff and leaching.  Accompanying the next release of the SWCC, the quality assurance and quality control (QA/QC) of this volatilization algorithm has been finalized.  This presentation will discuss the Environmental Fate and Effects Division’s evaluation of the algorithm and a comparison of the model’s results to flux estimates derived from field volatility studies.