HR: 1330h
AN: H13B-08    [Abstracts]
TI: Evaluating Groundwater Pesticide Loading Using 1-D Vadose Zone Models
AU: * Angier, J T
EM: Angier.Jonathan@EPA.gov
AF: US-EPA/OPPTS, 1200 Pennsylvania Ave., N.W. Mail Code #7507C, Washington, DC 20460 United States
AU: Young, D F
EM: Young.Dirk@EPA.gov
AF: US-EPA/OPPTS, 1200 Pennsylvania Ave., N.W. Mail Code #7507C, Washington, DC 20460 United States
AB: A major pathway for pesticide entry into groundwater is through the vadose (unsaturated) zone. In the absence of reliable monitoring data, computer models are often used to estimate pesticide concentrations in ground water. Models that attempt to provide usable values for predicted groundwater pesticide concentrations need to incorporate several crucial parameters, including information on soil properties, hydrologic conditions, geomorphology, meteorological data, water table depths, crop types, and pesticide usage patterns. Preferential flow (e.g., through macropores) within the vadose zone must also be considered. In this study, three models, PRZM, RZWQM, and LEACHP, were evaluated for the purpose of estimating groundwater pesticide loading through the vadose zone. Methods, such as using deep vadose zone pore water chemical concentrations as a surrogate for shallow groundwater concentrations, and modeling/integrating macropore flow contributions to groundwater, were explored. Values obtained from these models were compared with field-collected groundwater data to determine the suitability of methodology and relative accuracy of each predictive model. Preliminary data indicate that, at least under near-steady-state conditions (that is, in the absence of major rainfall events that would trigger substantial macropore flow), vadose zone pore water concentrations generally reflect shallow groundwater concentrations. This abstract has been subjected to review by EPA's Office of Pesticide Programs and was approved for submission. Approval does not signify the contents reflect the views of EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.
DE: 1803 Anthropogenic effects
DE: 1831 Groundwater quality
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2005 Joint Assembly