A PRELIMINARY GEOCHEMICAL ANALYSIS OF SPATIAL AND TEMPORAL VARIATIONS IN THE SURFACE WATER CHEMISTRY OF RICE COUNTY MINNESOTA USING ArcGIS

Rice County, located in south-east Minnesota, is home to a very complex surface water system. The western portion of the county is largely covered by lakes, while the eastern segment is predominantly farmland cut up by streams and agricultural drainage tiles. This study evaluates the inorganic water quality of the region in order to assess the geological and anthropogenic factors affecting the water system. From summer 2008 to summer 2009, 260 water samples were collected. Using Dionex 600 Ion Chromatography, samples were tested for six cations (Na⁺, K⁺, Mg⁺, Ca²⁺, Li⁺, NH³⁺) and seven anions (Fl^-, Cl^-, Br^-, NO₂, NO₃^-, PO₄^3-, SO₄^2-). In ArcGIS we sorted and analyzed the sample locations by drainage area. With Kriging interpolation, we created comprehensive chemistry maps of the county to analyze the spatial variance of these ions. The lakes show concentrations in the normal ranges; streams and rivers in the east, however, tend to show high concentrations of NO₃^-, indicating significant agricultural input. While it is difficult to determine the ecological impact of the dissolved material using the data from this study alone, further research into the ground water system in conjunction with this data will provide the full impact of anthropogenic pollutants on the waters of Rice County.