Trace Metal Mobility in the Yellow Pine Mining District, Idaho Completed

Sources/Usage: Public Domain. View Media Details

Science Issue and Relevance

The Yellow Pine mining district, at the headwaters of the East Fork South Fork Salmon River (EFSFSR) has had historic antimony, mercury, tungsten, and gold mining activity since the early 20th Century. The EFSFSR provides critical habitat for spawning Chinook salmon, steelhead trout, and bull trout, and is a tributary in the Snake River watershed. The historical Cinnabar mercury mine site is at the headwaters of Cinnabar Creek, a tributary to Sugar Creek. An integrated study to characterize the site creates a body of science that stakeholders can apply to inform land use decisions, to help guide remediation efforts, and to plan for balanced resource management.

Methodology to Address Issue

The study objective is to conduct an integrated, interdisciplinary study on source areas, biogeochemical transformations, and physical and biological pathways for trace metal transport, focusing on the Sugar Creek watershed. Three tasks use different research questions and approaches to characterize and quantify trace metal sources and mobility.

Sources/Usage: Public Domain. View Media Details

Isotopic and Geochemical Characterization of Trace Metals - The application of a combination of non-traditional trace metal isotopes, including mercury, and isotopes associated with geologic sources, including lead and strontium, may prove an effective means of identifying source areas for mercury, which can have multiple sources, including legacy mining, combustion, and atmospheric deposition. A combination of trace metal and light stable isotopes will be used along with bulk chemistry of rock, stream sediment, and mine tailing samples to distinguish between background geologic concentrations of mercury and arsenic upstream from mining activity, and direct effects of historical mining on stream water and trace metal chemistry.

Biogeochemical Characterization of Mercury - Understanding the biogeochemical cycling in the context of the overall geochemical matrix of water, soil, and sediment is critical in understanding the fate and transport of both total mercury and the bioaccumulating neurotoxin methylmercury. The biogeochemistry of mercury will be addressed by:

• ​​​​​Physically and chemically characterizing wetlands in the Stibnite and Cinnabar areas, determining the concentrations and isotopic composition of mercury in the sediment and soil, and analyzing the methylmercury in water, sediment and soil
• Determining whether the mercury in down-gradient stream sediments can be directly traced to the mercury in the upland waste rock or wetland soils by measuring the magnitude of methylation in these downstream sites.

Methylmercury is the mercury species that is biologically available, and directly impacts human health through fish consumption.

Sources/Usage: Public Domain. View Media Details

Biological Uptake and Transport of Trace Metals - Salmon are a critical food source for the Nez Perce Tribe, particularly for the elderly and economically challenged members of the tribe. The extent to which salmon bioaccumulate arsenic and mercury from legacy mining sources has not been constrained in the East Fork South Fork Salmon River. Understanding how and where trace metals are accumulated by fish is critical in management of the overall watershed, including non-point sources from multiple legacy mining sources identified in the watershed. Our objective is to quantify the amount of trace metal uptake of benthic invertebrates (organisms that live on the bottom of a water body or in the sediment and have no backbone) and the transfer for these trace metals from stream sediment to terrestrial environments through spiders, and to fish through consumption of these benthic invertebrates. The further transport of trace metals through fish migratory pathways will also be investigated. This is particularly critical for salmon, which spend a sizable portion of their life cycle in marine environments. Understanding the movement and feeding areas of these fish will give some indication as to how much the salmon actually feed in upstream areas that are directly impacted by legacy mining. The bioavailability and mobility of trace metals characterized under Tasks 1 and 2 will be determined by chemical assays of invertebrate and fish tissues collected in cooperation with the Payette National Forest and the Nez Perce Tribe Fisheries Resources Management.

Return to Mineral Resources Program | Geology, Geophysics, and Geochemistry Science Center