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Trace elements in Corbicula fluminea from the San Joaquin River, California
1Water Resources Division, U.S. Geological Survey, Menlo Park, CA 94025.
The Science of the Total Environment
|November 1, 1990
Summary
This study examined trace element concentrations in the Corbicula fluminea bivalve in the San Joaquin River. Selenium and arsenic levels varied with water chemistry, while mercury and cadmium were elevated in specific tributaries.
Area of Science:
- Environmental Science
- Ecotoxicology
- Aquatic Biology
Background:
- The San Joaquin River system is vital for agriculture and water supply.
- Understanding trace element contamination is crucial for ecosystem health and human safety.
- The benthic bivalve Corbicula fluminea is a common indicator species in freshwater systems.
Purpose of the Study:
- To assess trace element concentrations in Corbicula fluminea soft tissues.
- To investigate the relationship between element levels in bivalves and riverwater/sediment chemistry.
- To identify spatial variations and potential sources of contamination in the San Joaquin River and its tributaries.
Main Methods:
- Collected Corbicula fluminea from the San Joaquin River and tributaries during the irrigation season.
- Analyzed trace element concentrations (Se, As, Hg, Cd, Cu, Ni, B, Mo, Cr, Pb, Ag, V, Zn) in bivalve tissues.
- Correlated bivalve element concentrations with water and sediment chemistry (major, minor, and trace constituents).
Main Results:
- Selenium concentrations in bivalves correlated with dissolved Se in riverwater, particularly near irrigation return flows.
- Arsenic accumulation in bivalves was linked to the As:Fe ratio in suspended matter, with higher levels in tributaries and upstream reaches.
- Mercury, cadmium, and copper showed elevated concentrations in specific tributaries and river sections, while nickel decreased downstream.
- Boron and molybdenum were not accumulated by Corbicula, suggesting it's not a suitable bioindicator for these elements.
- No synergistic or antagonistic interactions were found among the studied trace elements in bivalve uptake.
Conclusions:
- Trace element concentrations in Corbicula fluminea are influenced by water chemistry, sediment composition, and water source.
- Subsurface drainage and irrigation return flows are significant sources of selenium contamination.
- Sorption to oxyhydroxide surfaces controls arsenic bioavailability, but tributary geology also plays a role.
- Corbicula fluminea can indicate contamination by Se, As, Hg, Cd, and Cu, but not B or Mo.
- Further research is needed to understand the ecological impacts of these trace elements.