FRACTIONATION OF METALS IN CONTAMINATED SEDIMENTS WITHIN THE TRI STATE MINING DISTRICT

Mining stopped approximately 70 years ago in the Tri State Mining District (TSMD) of Kansas, Oklahoma and Missouri. The Zn-Pb mineral deposits were emplaced over a large area with the abandoned wastes (chat piles) commonly located next to the mined areas. In Missouri, most of the chat piles have been removed and former mining sites have been remediated by phytostabilization. However, high concentrations of Zn Pb and Cd continue to be observed in some stream sediments. Metals preferably adsorb onto the solid phase (sediment) and accumulate there. The dispersion and the amount of metal that could be remobilized is determined by fractionation, a method that includes sequential extraction with solutions of increasing strength to determine how much of the total metal would be released under specific conditions of pH, oxidation state, and/or the presence of other chemicals. Fractionation within the TSMD is discussed based on data reported by Schaider et al. (2007, 2014), Pearson (2017), and ongoing studies by the author and her students. These data are also used to estimate the amount of metal that would be released under a variety of applied and foreseen remediation procedures within the TSMD.