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NSF: Mercury-laden fog swirls over coastal California, scientists find

What do the roof of a building in a West Coast redwood forest, a bluff in California chaparral, and a research vessel in Monterey Bay have in common? They're often draped in tendrils of fog. That makes them prime sites for collecting fog water samples. And there's something else that can be found at those sites: mercury, according to atmospheric chemist Peter Weiss-Penzias of the University of California at Santa Cruz (UCSC).

Sea fog is a significant, but previously overlooked, source of toxic monomethyl mercury deposited in coastal environments, Weiss-Penzias and colleagues reported at the December 2014, American Geophysical Union (AGU) Fall Meeting in San Francisco.

Their research is funded by the National Science Foundation (NSF)'s Chemical Oceanography Program in its Division of Ocean Sciences.

"'Fog drip' could deliver unsafe levels of monomethyl mercury to upland and near-shore ecosystems along the Pacific Coast," Weiss-Penzias says.

Other scientists had previously found high levels of mercury in Monterey Bay during coastal upwelling events--occasions when winds drive surface water offshore and colder water from the deep moves in to replace it. That gave Weiss-Penzias and colleagues the idea to find out whether mercury was somehow stealing ashore in fog.