Trace metals in sediments of a mine impacted river basin: Clear Creek California project
Moore JN and Hughes D. 2003. Trace metals in sediments of a mine impacted river basin: Clear Creek California project
Authors' Abstract: "Chemical composition of fine-grained channel bed sediments (<63 micrometers) collected in 2003 was compared to samples collected in 2001 and 2002 to assess metal contamination of the Clear Creek watershed. Samples collected in 2001 & 2003 followed higher flows while 2002 samples were collected during a continual low flow period. Sediment samples collected throughout Clear Creek and its major tributaries were analyzed for various metals including As, Cd, Cr, Cu, Hg, Pb, and Zn, which signify contamination from mining to the watershed. Background/baseline levels were determined from un-mined tributaries, national sediment averages and NOAA Apparent Effects Thresholds, and it was found that certain elements were elevated compared to these values. To understand the extent of contamination, sampling extended from the uppermost part of the basin beyond where most mining was known to occur, downstream through Whiskeytown National Recreation Area, where several tributaries were sampled, into the Clear Creek “Gorge,” and ended at the confluence with the Sacramento River. The results show that different metals are of concern in different sections of the basin. Potential toxicity from an element may be extremely localized, down to one specific site or may extend up to several miles downstream from the source. In the Upper basin arsenic, copper, lead and mercury are of primary concern. Cadmium, lead, zinc, mercury, and selenium are elevated in the vicinity of Whiskeytown Lake, where Clear Creek and it’s tributaries are supplying metalcontaminated sediment to Whiskeytown Lake. Clear Creek Gorge had relatively low concentrations of metals. Lower Clear Creek, in general had far less metal contamination than in the upstream sites, however, some localized areas had elevated metal concentrations. While no one metal is of concern throughout Clear Creek watershed, some metals should be monitored in specific areas of the basin. Several “hotspots” within the basin are located downstream of active mines or tailings piles, which are likely sources of contamination."
- Type
- Unpublished Report
- Authors
- Moore, Johnnie; Hughes, Danielle
- Date of Issue
- 2003-12-30
- Units
- WHIS
- Keywords
- Chemicals, Clear Creek, Contamination, fine grain, flow level, Health, IAR, Metals, Mines, Mining, Sacramento River, Sediment, Sedimentology, Stratigraphy, Toxicity, Watershed