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Copper speciation in variably toxic sediments at the Ely Copper Mine, Vermont, United States

January 6, 2016

At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160–1200 times) and sediments (15–79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80–95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

Publication Year 2016
Title Copper speciation in variably toxic sediments at the Ely Copper Mine, Vermont, United States
DOI 10.1021/acs.est.5b04081
Authors Bryn E. Kimball, Andrea L. Foster, Robert R. Seal, Nadine M. Piatak, Samuel M. Webb, Jane M. Hammarstrom
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science & Technology
Index ID 70168662
Record Source USGS Publications Warehouse
USGS Organization Eastern Mineral and Environmental Resources Science Center; Geology, Minerals, Energy, and Geophysics Science Center