Geology topics
Irene R. Lavigne
Publications and source records attributed to Irene R. Lavigne.
Near field receiving water monitoring of trace metals in clams (Macoma balthica) and sediments near the Palo Alto water quality control plant in south San Francisco Bay, California: 2002
This report presents trace element concentrations analyzed on samples of fine-grained sediments and clams ( Macoma balthica ) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study, which was started in 1994. The data for 2002, herein, are interpreted within that context. Metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability. However, copper and zinc, display continued decreases. Copper in sediment was observed to drop below the ERL (Effects Range-Low) concentration for the third consecutive year and zinc concentrations never exceeded the ERL. Yearly average concentrations of copper, zinc and silver in Macoma balthica for 2002 are some of the lowest recorded since monitoring began in 1975. Mercury and selenium concentrations in sediments and clams at Palo Alto were similar concentrations observed elsewhere in the San Francisco Bay.
Near field receiving water monitoring of trace metals in clams (macoma balthica) and sediments near the Palo Alto Water Quality Control Plant in South San Francisco Bay, California: 1999-2001
This report presents trace element concentrations analyzed on samples of fine-grained sediments and clams (Macoma balthica) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study which was started in 1994. The data for 1999-2001 are interpreted within that context. Generally, metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability. Copper and zinc, however, display a continued decrease, recording the lowest winter maxima concentrations in both sediment and tissue samples in 2001. Yearly average of bioavailable copper, zinc and silver concentrations in 1999-2001 are some of the lowest recorded since monitoring began in 1975. A slight increase in mercury in sediments and selenium in tissue in early 2001 are also observed. These enrichments are believed to be mainly caused by hydrogeologic processes affecting the area although only continued sampling will confirm whether anthropogenic sources influence the concentrations of these elements.