T8 The Animas River and Beyond: Balancing Science and Policy in Cleaning up America’s Abandoned Mine Lands

Sunday, 25 September 2016
8:00 AM - 12:00 PM
Room 403

BIOGEOCHEMICAL PROCESSES AFFECTING METAL CYCLING ALONG THE ANIMAS RIVER

Paper number: T8-13
Program: Technical Sessions
Time: 11:00 AM – 11:15 AM

Authors

Abstract

The Animas River is known to be affected by natural mineralization and extensive mining activity since 1871. The river flows from a heavily mineralized area (San Juan Mountain, CO) to an intensive agricultural area (Farmington, NM), where it drains into the San Juan River. Lead and As total concentrations exceed national drinking water standards along the Animas and San Juan River after high-flow events.

Biogeochemical cycling of metals in the Animas River was investigated using spectroscopy, microscopy, diffraction, molecular biology, and water chemistry methods. Water and sediment samples were collected 13-14 days after the Gold King Mine spill (August 5, 2015). Microbial community changes in the sediments were assessed using Next-Generation Sequencing.

Metal concentrations in the sediments are higher in the Upper Animas River watershed (mean concentrations of 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 in sediments from Cement Creek, the tributary of the Animas River where the spill occurred), decreasing as the Animas River flows downstream. Contrarily, microbial diversity is low upstream and it increases downstream the Animas River. Solid-phase characterization suggest that Pb, Cu, and Zn are associated with clays, Fe-(oxy)hydroxides, and metal-bearing jarosite [Me-Fe3+3(OH)6(SO4)2] which is stable under low pH. Phosphate and nitrogen species were found in water and sediments in Farmington, NM. In addition, Fe-oxidizing microorganisms were detected in the sediments from Cement Creek, while N-cycling bacteria where found in the sediments from Farmington, NM. The solubility of jarosite at near-neutral pH and biogeochemical processes occurring downstream could affect the remobilization of metals in sediments. Because the Animas River flows through different environmental systems, this study has unique implications to understand the long-term metal release caused by recurrent contamination in river basins in semi-arid regions.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-286555

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