Preliminary Report on Mercury Geochemistry of Placer Gold Dredge Tailings, Sediments, Bedrock, and Waters in the Clear Creek Restoration Area, Shasta County, California

Abstract Clear Creek, one of the major tributaries of the upper Sacramento River, drains the eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the northwest edge of the Sacramento Valley, contain placer gold that has been mined since the Gold Rush by various methods including dredging. In addition, from the 1950s to the 1980s aggregate-mining operations removed gravel from the lower Clear Creek flood plain. Since Clear Creek is an important stream for salmon production, a habitat restoration program is underway to repair damage from mining and improve conditions for spawning. This program includes using dredge tailings to fill in gravel pits in the flood plain, raising the concern...

Contaminant impacts on Pacific lamprey

Cooperative Study: Reconnaissance of Emerging and Legacy Contaminants in the Habitat and Tissues of the Pacific Lamprey in the Columbia River Basin

Mercury Bioaccumulation in Pacific Lamprey Ammocoetes: the Role of Life History

Abstract Stream sediments in several subwatersheds of the Guadalupe River drainage are contaminated with mercury (Hg) at concentrations exceeding hazardous waste criteria due to historic mining operations. From 1995-1998 we collected sediment, benthic macroinvertebrates, crayfish, and fish samples at sites with different mining histories and analyzed them for total mercury (T-Hg) and/or methylmercury (M-Hg). Fish and invertebrate Hg concentrations at each site were correlated with sediment T-Hg and to T- Hg in other species. We found Pacific lamprey (Lampetra tridentata) ammocoetes at the lowest elevation sites in three of the subwatersheds. Mercury concentrations in ammocoete tissues were positively correlated...