A LEGACY OF PERSISTENT LEAD CONTAMINATION IN AND NEAR HISTORICALLY MINED AREAS IN THE CENTRAL U.S

Historical lead (Pb) mining in the Tri-State Mining District (TSMD) of southeast Kansas, southwest Missouri, and northeast Oklahoma ended in the 1970s after about 100 years of production. Today, the formerly mined areas continue to serve as a substantial source of Pb to the environment. In the areas that were most affected by mining, streambed, lakebed, and floodplain sediments typically have Pb concentrations that exceed probable-effects guidelines, which represent the concentration above which toxic biological effects usually or frequently occur. Sediment cores from Empire Lake, located within the TSMD in southeast Kansas, indicate that Pb concentrations have declined with time but remain persistently above the probable-effects guidelines. Several kilometers downstream of the TSMD at Grand Lake O’ the Cherokees in northeast Oklahoma, a dilution effect is evidenced by Pb concentrations in the bottom sediment that are less than the probable-effects guidelines. At this lake, the Pb concentrations are greater than the threshold-effects guideline, which represents the concentration above which toxic biological effects occasionally occur. Within the mining-affected areas, Pb contamination is pronounced in the tributary floodplains but mostly absent in the mainstem Spring River floodplain. Biota adversely affected by the mining-related contamination include mussels, waterfowl, and fish. Human health problems and risks also have been attributed to the mining-related contamination. In this paper, the magnitude, spatial variability (surficially and with depth), and temporal variability of Pb contamination is described and explained in the context of fluvial processes. An understanding of the environmental fate of mining-related Pb is important for the development and implementation of remediation and restoration plans.