MAPPING OF PB- AND ZN-CONTAMINATED STREAM SEDIMENTS

Pb and Zn concentrations in stream sediments of the Tri-State Mining District in Missouri were spatially analyzed to determine both the contamination level and dispersion of these metals. Background concentrations were obtained from stream sediment concentrations reported in the USGS Geochemical Database (N = 1,019). Next, publically available metal content data for each of four historic mining sites were compared against the background concentration using geochemical mapping interpolation (IDW method), box plot diagrams, Pearson correlation and ratioing. Pb and Zn median concentration of background were of 22.0 and 53.0 mg kg^-1 respectively. Two sites (Joplin and Aurora) were up to 40 times higher than the background concentrations, while the other two sites (Springfield and James River) were close to background concentrations. The metal content maps and association among metals both indicate that mining wastes are the main source of contamination, even though mining ceased over 40 years ago and remediation has been applied to soils. The usefulness of publically available data and the potential threat to aquatic habitat are emphasized.