Hierarchical approach for obtaining values of physical and chemical parameters controlling the transport and fate of pesticides and their transformation products in the hydrologic system

AGRO 103

Jack E. Barbash, jbarbash@usgs.gov1, Paul D. Capel2, Tracy Connell Hancock2, and Karen C. Rice2. (1) National Water-Quality Assessment (NAWQA) Pesticide National Synthesis Team, U. S. Geological Survey, 934 Broadway, Suite 300, Tacoma, WA 98402, (2) U.S. Geological Survey, University of Minnesota, 122 Civil Engineering Building, 500 Pillsbury Dr. S.E, Minneapolis, MN 55455
Results from mathematical simulations of contaminant transport and fate in the hydrologic system have been published for over three decades, but numerical values for many of the physical and chemical parameters that such models require are rare or absent for many anthropogenic compounds of interest, especially transformation products. A hierarchical approach is therefore proposed to obtain values for water solubility, Henry's law constant, and several other key parameters of interest, using pesticides and their transformation products as illustrative examples. Critically reviewed, measured parameter values from the literature receive highest priority. Quantitative property-property relations are used when values are available for some parameters but not others. If needed, quantitative structure-property relations are used to calculate parameter values de novo, or to estimate them by adjusting literature values for structurally similar compounds. The approach also specifies standard conditions for the parameters of interest and, where necessary, adjusts parameter values to these conditions.