10.2190/06FQ-E7CB-434Y-5DQA 06FQE7CB434Y5DQA 1 A Spatially Varied Index Method to Define Relative Risks Associated with Pesticide Contamination of Groundwaters 111 135 20020509 20020509 20020509 20020509 06FQE7CB434Y5DQA.pdf http://baywood.metapress.com/link.asp?target=contribution&id=06FQE7CB434Y5DQA 2 B. T. Daniels W. F. McTernan Maxim Technologies, Inc., Houston, Texas Oklahoma State University, Stillwater <p>In order to assess groundwater contamination from pesticides, a method was developed and applied to a large section of the state of Oklahoma. The method, which is titled the PESTICIDE RISK INDEX, used the DRASTIC Index along with pertinent data defining Oklahoma's hydrogeological and agricultural conditions to identify areas with the potential for contamination. The probability and extent of leaching for various soil and pesticide combinations found in Oklahoma were defined with a Monte Carlo analysis of 540 years of simulated field conditions using the Pesticide Root Zone Model (PRZM). The risk of human exposure to contaminated sources of drinking water was assessed by consideration of the Environmental Protection Agency's Reference Doses for selected pesticides, and the groundwater usage statistics for Oklahoma. The Index resulted in a series of maps which identified the locations of greatest relative susceptibility.</p><p>The Pesticide Risk Index identified three areas of Oklahoma with potential high risk for exposure to pesticide contaminated groundwater. The Monte Carlo analysis indicated that certain site and chemical pairings could result in significant leaching. It was found that soil retardance was the most determinant factor in the leaching of pesticides.</p> R. F. Carsel, C. N. Smith, L. A. Mulkey, J. D. Dean, and P. P. Jowise, <i>Users Manual for the Pesticide Root Zone Model (PRZM)</i>, Office of Research and Development, U. S. Environmental Protection Agency, Athens, Georgia, 1984. J. D. Dean, P. P. Jowise, and A. S. Donigian, Jr., <i>Leaching Evaluation of Agricultural Chemicals (LEACH) Handbook</i>, EPA-600/3-84-068, Environmental Research Laboratory, U. S. Environmental Protection Agency, Athens, Georgia, 1984. L. Aller, T. Bennet, J. H. Lehr, and R. J. Petty, <i>Drastic: A Standardized System for Evaluating Groundwater Pollution Potential Using Hydrogeologic Settings</i>, Robert S. Kerr Environmental Research Laboratory, U. S. Environmental Protection Agency, Ada, Oklahoma, 1985. W. F. McTernan, <i>Evaluation of Existing EPA Methods to Predict Groundwater Pollution Potentials from Pesticide Applications</i>, report to EPA/AAAS Environmental Science and Engineering Program, Washington, D. C., 1985. W. A. Pettyjohn, H. White, and S. Dunn, <i>Water Atlas of Oklahoma</i>, University Center for Water Research, Oklahoma State University, Stillwater, Oklahoma, 1983. F. Gray and H. M. Galloway, <i>Soils of Oklahoma</i>, miscellaneous publications, Agricultural Research, Oklahoma State University, Stillwater, Oklahoma, 1969. F. Gray and M. H. Roozitalab, <i>Benchmark and Key Soils of Oklahoma</i>, Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma, undated. R. Morton, personal communication, 1986. R. F. Carsel, R. S. Parrish, R. L. Jones, J. L. Hansen, and R. L. Lamb, Characterizing the Uncertainty of Pesticide Leaching in Agricultural Soils, <i>Journal of Contaminant Hydrology, 2</i>:2, 1988. R. F. Carsel, M. N. Lorber, and L. B. Baskin, The Pesticide Root Zone Model (PRZM): A Procedure for Evaluating Pesticide Leaching Threats to Groundwater, <i>Ecological Modeling, 30</i>, pp. 49-69, 1985. L. Smith, <i>Stochastic Models of Fluid Flow in Heterogeneous Media. Soil Spatial Variability</i>, Pudoc Wageningen, The Netherlands, pp. 96-110, 1985. P. W. Lai and A. M. Vevers, Ammonia Modeling for the Rother Catchment: The Monte Carlo Approach, <i>Water Pollution Control, 85</i>:3, pp. 316-321, 1986. J. E. Cochrane and J. H. Waldrop, <i>Oklahoma Agricultural Statistics Oklahoma for 1981</i>, Oklahoma Department of Agriculture, 1981. J. T. Criswell, <i>Use of Pesticides on Major Crops in Oklahoma, 1981</i>, Research Report P-833, Division of Agriculture, Oklahoma State University, Stillwater, Oklahoma, 1982. E. J. Gumbel, <i>Statistics of Extremes</i>, Columbia University Press, New York, 1958. A. W. Olivieri, D. E. Eisenberg, and R. C. Cooper, Groundwater Contamination Site Ranking Methodology, <i>Journal of Environmental Engineering, 112</i>:4, pp. 757-769, 1986.