INFORMING ACTIVIST AGENDAS BY DOCUMENTING HISTORIC AND CURRENT TRANSPORT PATHWAYS OF LEGACY METALS AT THE TAR CREEK SUPERFUND SITE, OK

The communities surrounding the Tar Creek Superfund Site in Ottawa County, Oklahoma continue to be contaminated with zinc, lead, cadmium, and manganese from large mine waste (chat) piles and acid mine seepage. The surface waters at, and downstream, of these mining sites are influenced by complex interactions between the multiple contaminate sources and biogeochemical conditions. Previous research has shown that surface mine waste pile (MWP) runoff contributed to 70% of Cd loading, while mine drainage (MD) contributed 90% of Pb loading, and both sources contributed similarly to Zn loading. They estimated annual loading into sediments to be 8800 kg/y Zn, 160 kg/y Pb, and 15 kg/y Cd, with iron oxides (annual loading of 160,000 kg/y Fe) acting as a vector for metal transport into floodplain soils.

In partnership with local activists, we explored a combination of wetland and river bank sediment cores along with floodplain soil transects, and examined legacy metal transport linked with both steady state runoffs and high flow events like overbank flooding. All sediment and soil samples were air dried and homogenized by hand in ceramic mortar and pestle. Samples were analyzed using pED-XRF (Spectro XEPOS-He) and flash combustion (Elementar CHNS Vario Micro Cube). We found evidence of current and historical metal transport throughout the watershed, which also demonstrated temporal trends. MWP runoff and MD sources can be geochemically fingerprinted using trace elements, and their contributions can be apportioned throughout the watershed.

We have previously documented that mining-derived metals are deposited onto floodplain soil during major flooding events. As a result, we aim to investigate the solubility of floodplain soil metals in the event that they are submerged. The impending relicensing of the Pensacola Dam, which would raise water levels by 2 ft, will increase the potential and severity of flooding. This makes the development of low-cost, user-friendly methods to measure mobilized legacy metal concentrations in floodplain soils when exposed to water critical. We aim to identify remediation interventions that reduce environmental and public health risk.