Metal concentrations in seston and water in the Clark Fork River, MT

Legacy mine waste from the Clark Fork River in Western Montana has contributed 100 million tons of tailings into the watershed between 1880 and 1982 (E.D. Andrews, Longitudinal dispersion of metals in the Clark Fork River, Montana, Lewis Publishers, 1987). Tailings deposited along the floodplain, streambanks and river channel continue to contribute metal contaminated material into the river in the form of metal-enriched particulate matter or seston, comprising a mixture of organic and inorganic materials (J.N. Moore and S.N. Luoma, Hazardous wastes from large-scale metal extraction: A case study. Environmental Science and Technology, v.24:1278-1285, 1990). Metal enriched seston poses a dietary exposure risk to filter-feeding macroinvertebrates that entrap and ingest suspended materials as a primary food source. Suspended particulate material and dissolved and total recoverable water samples were collected along a metal contamination gradient in 2017 and 2018 in the Clark Fork River and analyzed for metal concentrations to include the highly toxic metals arsenic, cadmium, and copper. Concentrations of seston arsenic (As), cadmium (Cd), and copper (Cu) ranged from 20.7–242 ug As/g, 2.7–16.2 ug Cd/g, and 129–1260 ug Cu/g. Dissolved (filtered) stream water concentrations ranged from 3.5–21.7 ug As/L, 0.1–0.38 ug Cd/L, and 1.5–12.5 ug Cu/L. Total recoverable (unfiltered) water concentrations ranged from 2.7–22.8 ug As/L, 0.1–0.35 ug Cd/L, and 2.0–14.9 ug Cu/L. Data presented here represent metal concentrations in water and seston from a mining-impacted river and provide insight to potential exposure of toxic metals to resident filter-feeding aquatic invertebrates.

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                                            {
  "fn": "Michelle I Hornberger",
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                                            [
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