( The highest levels of silver contaminat...)Survey finds silver contamination in North Pacific waters

The highest levels of silver contamination ever observed in the open ocean turned up in samples collected during a survey of the North Pacific in 2002. Researchers from the University of California, Santa Cruz, measured silver concentrations 50 times greater than the natural background level. Though still well below levels that would be toxic to marine life, this contamination of what had been considered relatively pristine waters highlights the increasingly global impact of industrial emissions from Asia, the researchers said.

"The most likely source of the silver contamination is atmospheric emissions from coal burning in Asia," said Russell Flegal, professor of environmental toxicology at UCSC. "Silver concentrations in the North Pacific trace the atmospheric depositions of industrial aerosols from Asia, with the highest concentrations in those waters closest to the Asian mainland."

Mara Ranville, a researcher in Flegal's lab who earned her Ph.D. in December, collected the samples on a 35-day cruise in the summer of 2002 as part of the Global Investigation of Pollution in the Marine Environment (GIPME), a program of the UNESCO Intergovernmental Oceanographic Commission. Ranville and Flegal reported their findings in the March 9 issue of Geochemistry, Geophysics, Geosystems, an electronic journal published by the American Geophysical Union and the Geochemical Society.

Ranville found silver concentrations as high as 1.2 parts per trillion in samples of North Pacific surface waters taken during the cruise. This is about 50 times higher than baseline levels of silver in uncontaminated waters sampled by UCSC researchers on a previous cruise in the Atlantic Ocean. Because the natural background level is so low, scientists may be able to use silver as a tracer element for tracking the fate of industrial emissions from Asia, Ranville said.

"Atmospheric pollution from Asia is becoming a serious problem for the western United States, and this
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Source:University of California - Santa Cruz

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