Post Gold King Mine spill investigation of metal stability in water and sediments of the Animas River watershed

摘要

We applied spectroscopy, microscopy, diffraction, and aqueous chemistry methods to investigate the persistence of metals in water and sediments from the Animas River 13 days after the Gold King Mine spill (August 5, 2015). The Upper Animas River watershed, located in San Juan CO, is heavily mineralized and impacted by acid mine drainage, with low pH water and elevated metal concentrations in sediments (108.4±1.8 mg kg⁻¹ Pb, 32.4±0.5 mg kg⁻¹ Cu, 729.6±5.7 mg kg⁻¹ Zn and 51,314.6±295.4 mg kg⁻¹ Fe). Phosphate and nitrogen species were detected in water and sediment samples from Farmington, NM, an intensive agricultural area downstream from the Animas River, while metal concentrations were low compared to those observed upstream. Solid-phase analyses of sediments suggest that Pb, Cu, and Zn are associated with metal-bearing jarosite and other minerals (e.g. clays, Fe-(oxy)hydroxides). The solubility of jarosite at near-neutral pH and biogeochemical processes occurring downstream could affect the stability of metal-bearing minerals in river sediments. This study contributes relevant information about the association of metal mixtures in a heavy mineralized semi-arid region, providing a foundation to better understand long-term metal release in a public and agricultural water supply.