Understanding Subsurface Transformations and Dynamics of Trace Elements in Multi-Metal Contaminated Mine Waste Materials in Southeast Kansas.

The Neosho River and its tributaries in southeast Kansas are contaminated with lead (Pb), zinc (Zn), and cadmium (Cd), due to historic mining activities conducted in the Tri-State mining district. Trace metal transformations and cycling in mine waste/soils could greatly influence ecosystem and human health. It has been hypothesized that under reducing conditions in sulfate rich environments, these metals can be transformed into their sulfide forms limiting their mobility. Since, the existing mine tailings are inherently low in organic carbon (OC), the objective of our study was to examine the effect of OC, and sulfate addition on the biogeochemical transformations of Pb, Zn and Cd in these mine waste materials. To our knowledge, there are no research considering mechanisms of these transformation processes, interaction between OC, microbes, and sulfate and colloid-assisted metal transport to get better understanding for designing effective remediation and mitigation strategies for mine-scared areas. On-going column study indicated that upon reduction metals were effectively immobilized within 119 days of submergence. Scanning electron microscopy and energy dispersive x-ray analysis conducted on the effluent water’s micro and nano-size colloids provided the evidence that bacterial associated and freely dispersed colloidal bound contaminant transportation were still relevant. The combined kinetic and thermodynamic evaluation of effluent water chemistry will be presented. Investigations are under way to evaluate the hypothesis that long -term submergence of the existing mine tailings with sulfate and OC addition would greatly subside the trace metal mobility due to biogenic sulfide formation under stimulated reduced conditions.