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The aquatic ecosystems downstream of the former Black Butte Mine in Oregon are exposed to mercury contamination from historic mining activities, as well as mercury transported to the area through the atmosphere. 

Identifying the source of mercury (Hg) in contaminated sites is important for evaluating whether efforts aimed at reducing Hg contamination in the environment have been effective. Researchers measured Hg in soil, sediment, water, and fish from free-flowing segments of the Willamette River and a reservoir downstream from the former Black Butte Hg mine. The concentration of total Hg in fish collected from the reservoir was four times higher than in fish in free-flowing river further downstream. The researchers were able to distinguish between Hg from the mine and Hg from other sources and found that mine-sourced Hg had more of an influence on fish species that feed near the sediment compared to higher in the water column. Understanding the sources of Hg contamination, and how Hg moves through rivers and food webs, can help managers prioritize sites for clean-up efforts.  

Eckley, C.S., Eagles-Smith, C.A., Luxton, T., Hoffman, J., and Janssen, S.E., 2023, Using mercury stable isotope fractionation to identify the contribution of historical mercury mining sources present in downstream water, sediment and fish: Frontiers in Environmental Chemistry, v. 4, Online. 

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