Thursday, 10 November 2005 - 10:00 AM
316-7

Numerical Analysis of NDMA Leaching Risk in Landscape Soils with Reclaimed Wastewater Application.

Shinsuke Haruta, Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Japan, Jay Gan, Department of Environmental Sciences, University of Califolnia, Riverside, Riverside, CA 92521, and Jirka Simunek, Department of Environmental Sciences, University of California, Riverside, Riverside, CA 92521.

Treated wastewater usually contains N-Nitrosodimethylamine (NDMA), a carcinogenic nitrosamine compound that is a chlorination by-product. In this research, NDMA leaching risk in turfgrass soils irrigated with reclaimed wastewater was evaluated using Hydrus-1D. Hydrus-1D is a software package numerically simulating variable-saturated water flow, and solute and gas transport in soils. We first analyzed a short term experiment in which 14C-NDMA was used to study the distribution and dissipation of NDMA in in situ lysimeters under field conditions. Site specific first-order decay (K) and Henry's Law (H) constants were obtained using inverse parameter estimation. We further analyzed a long term lysimeter study in which turfgrass plots were irrigated with imported tertiary treated wastewater for four months. Using this long term experiment, we further improved estimates of K and H values. Finally, the experimentally validated numerical model with the above derived K and H values was used to systematically explore the risk of NDMA leaching under various conditions, including abnormal weather conditions (heavy rain events or continuous light rains) and high intensity irrigation. Sensitivity analysis was carried out to evaluate effects of various parameters, including K, H, and water retention parameters. Through this research, we identified major factors governing NDMA dissipation in turfgrass systems. This information will be valuable for improving our knowledge of ground water risks in using reclaimed wastewater for irrigating landscaped lands.

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