The concentration and speciation of major and trace elements contaminants in water and sediments of the Animas River was investigated in samples collected 13 days after the Gold King Mine spill occurred on August 5, 2015. A combination of spectroscopic, microscopic and water chemistry techniques was used to better understand the short-term impact of the spill, which will contribute to elucidate the long-term consequences of recurrent mine waste contamination events. The total concentrations of different constituents in the water reached typical background levels. For example, in Cement Creek, we measured total lead (3.3 μg l-1 Pb), copper (54.9 μg l-1 Cu) and zinc (2.9 μg l-1 Zn), iron (13.4 mg l-1 Fe), and sulfate (630.5 mg l-1 SO42-). However, we detected the presence of these metals in the 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). The predominance of clay, jarosite, and alumino-silicate minerals was determined by XRD analyses in these sediments, which are relevant primary minerals known to accumulate metals in the environment. Analyses using XPS detected the presence of sulfates and phosphates, Fe as 75% Fe2+ and 25% Fe3+, and 100% Pb2+. The co-occurrence of Pb, Cu, Zn and Fe with SO42- was identified in these sediments using TEM, confirming the presence of metal-bearing jarosite (KFe3+3(OH)6(SO4)2). The water at Cement Creek has a pH 3.3, thus, the detection of jarosite in sediments from this location confirms the stability of this metal-bearing phase under acidic conditions. The accumulation of metals in clays and precipitation as metal-bearing minerals highlight the relevance of understanding biogeochemical interactions to further asses the long-term stability of the contamination in the sediments of the Animas River watershed.

Investigation of the Gold King mine spill impact in water and sediments downstream of the Animas river

251st National Meeting (2016)

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