Temporal and Spatial Variations in Sediment Trace Metal Concentrations in Streams, Rivers, and a Reservoir near a Derelict Lead-Zinc Mining District

Abstract

Historic lead and zinc mining in the Tri-State Mining District has ceased, but the legacy of trace metal contamination (Cd, Cu, Ni, Pb, and Zn) throughout the region still exists. This thesis focuses on stream sediments in and downstream from contaminated areas. This study evaluated temporal changes of trace metal concentrations over 35-years in Tar Creek sediments. The spatial distribution of trace metal concentrations was subject to analyses between Tar Creek, the Neosho River, the Spring River, and Grand Lake O’ the Cherokees. The last study focused on the bioavailability of trace metals in sediments and what factors may influence it. The watershed of Grand Lake O’ the Cherokees drains multiple National Priority List Superfund sites from miningrelated activities. Sources of trace metals entering the surface water systems include artesian flowing mine drainage, mining waste pile leachate, and mine waste in the active channels. When evaluating temporal changes in Tar Creek sediments, Cd, Mn, Ni, and Zn concentrations and organic carbon content increased. At the same time, Fe, Pb, and S decreased from 1985 to 2020. Spatially, Cd, Pb, and Zn concentrations decreased with increasing distance from mining impaired areas. Lastly, evaluating the impact of sediment pH, sediment organic carbon, and total Fe concentrations resulted in a wide range of responses and variability. The bioavailable concentrations of trace metals were not influenced equally by these factors. Use of statistical evaluations at the 95th confidence interval for the appropriate tests allowed for the determination of significance. Sediment-bound trace metals in freshwater sediments have complex behaviors and are becoming distributed downstream of the mining district. As remediation of sediments in the Superfund sites begins, it is imperative to understand the sources, mobility, and bioavailability of the trace metals to increase the effectiveness and efficiency of remediation while minimizing potential human and environmental risks.