A BACKGROUND SOILS GEOCHEMISTRY DATABASE FOR THE SRS

To aid in future monitoring and remediation studies it is essential to know the natural background concentrations of individual major and trace analytes of interest. Site-specific background values are typically reported in remediation studies, but these values may be biased by point source contaminants or they may contain statistical anomalies based on sampling bias. A site-wide background soils geochemistry database was created for the Department of Energy's Savannah River Site (SRS) to characterize the distribution of analyte concentrations in surficial (0-1') soils and in cores (up to 60 ' deep). A small subset of metals (Al, Cr, Fe, Pb and Zn) was used in our initial treatment of the database. A minimized-means declustering routine was employed to remove spatial bias from the data set introduced by intense sampling that invariably occurred around operable (contaminated) units. In contrast to the analysis of raw data, which produced anomalously high concentration peaks near the operable units, the declustered data predicted concentration values that were consistent with background samples collected far from the operable units. The declustered values were then used to calculate percentile ranges, which in turn, were used to classify the raw data within a GIS framework. This procedure permits the GIS to be interrogated in various ways to determine the natural and anthropogenic attributes that are most closely linked to the metal concentrations in soils of the SRS.