Tuesday, November 14, 2006

Inferring Relevance of Matrix and Preferential Flow Processes from Multi-Year Well Concentration Data.

Timothy Gish1, King-Jau Kung2, and Craig S. Daughtry1. (1) USDA/ARS Hydrology & Remote Sensing, Building 007, Room 104, Beltsville, MD 20705, (2) Rm 74 Soils, 1525 Observatory, Department of Soil Science, University of Wisconsin, Dept. of Soil Science, Madison, WI 53706

Preferential and matrix flow are the two dominate processes influencing chemical transport to groundwater.  Unfortunately the relevance of these processes is difficult to quantify without chemical flux data.  Seventy-one observations times from 31, 3-m wells were evaluated to determine relevance of preferential and matrix flow processes.  Spatial and temporal dynamics of atrazine, deethyl-atrazine, metolachlor, phosphorous, and nitrate were monitored over three and a half years.  A protocol for statistically evaluating multi-year well observations is presented and discussed.  Results indicate that mobile compounds indicate little structure in their transport and as a consequence are responsive to both matrix and preferential flow processes.  On the other hand, compounds which have an affinity for the soil matrix appear to be structured and heavily influenced by preferential flow.