University of California Santa Cruz researchers on Tuesday announced they detected a highly toxic form of mercury in groundwater flows at two coastal sites in California.
The groundwater at Stinson Beach in Marin County and Elkhorn Slough in Monterey County appears to contain relatively high levels of methylmercury, a neurotoxin that accumulates in long-living fish.
The researchers who led the California Sea Grant-funded project believe the groundwater flows represents a significant and previously overlooked source of mercury in the nearshore marine environment.
Published in the journal Environmental Science and Technology, the findings also show that submarine groundwater flows at the two sites inject about as much mercury into coastal waters as atmospheric deposition.
While previous studies have found methylmercury in terrestrial groundwater, few have documented the toxin in coastal waters.
"The big question for public health is, 'Where is all the mercury in seafood coming from?'" said co-author Russell Flegal, a professor of environmental toxicology at UC Santa Cruz. "What we have shown is that methylmercury is coming from groundwater in California at surprisingly high levels."
While the research team did not attempt to identify the mercury sources, it is possible that inorganic mercury is coming from natural processes like weathering of mercury-containing rocks, as well as human activities such as mining. Septic tanks in the vicinity of Stinson Beach may be contributing to the formation of inorganic mercury to methylmercury.
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June 9, 2009
