Mercury found in fish from S.F. water supply -- is China to blame?

San Francisco Chronicle / July 7, 2010

When researchers wanted to test largemouth bass at Lower Crystal Springs Reservoir for mercury levels, the reservoir's managers in San Francisco figured the scientists were simply looking for a clean sample to compare with toxic results at other spots.

Instead, the study showed that the fish in the San Mateo County lake - which collects rainwater as well as water piped in from Yosemite's Hetch Hetchy reservoir - had some of the highest mercury levels in the state.

Now, the San Francisco Public Utilities Commission, which oversees Crystal Springs and the rest of the sprawling network that supplies drinking water to 2.5 million people in San Francisco, San Mateo, Santa Clara and Alameda counties, is trying to find the source of the heavy metal, a neurotoxin that can cause developmental damage in children and brain, lung and kidney problems in adults.

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Mercury in the Crystal Springs area may be coming from a source other than local sediments, according to (Jay Davis and Tim Ramirez, senior scientist and manager for natural resources and land management at the San Francisco Public Utilities Commission). Both men theorize that instead of leaching out of rocks and soil, the mercury may be wafting across the Pacific Ocean from China. China relies heavily on energy from coal-fired plants, a major source of mercury pollution.

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/07/07/MNU41E4CR4.DTL

Davis continues: "It seems like a case where atmospheric deposition might play a role..."

There was a study done a few years ago on the ever-earlier melt-offs in the Sierras, which has accelerated over the past 15 years. Many people assume that it's due to global warming, but the study actually showed that particulate pollution is playing a greater role than atmospheric temperatures. The particulate pollution settles on the snow (and is often trapped within the snow itself as it's forming), reducing its reflectivity, increasing its heat absorption, and speeding its melt rates.

When they tested the particulates themselves, they found that nearly half were of trans-Pacific origin. To be fair, the remainder was from more local pollution sources, primarily in the California Central Valley. The problem, though, is that domestic pollution levels in California have actually decreased over the past 20 years as cars have become cleaner and the state has de-industrialized, so nearly all of the particulate increase seems to stem from Chinese industrial pollution and dust from western Chinese desertification. The stuff floats across the Pacific, and the various Pacific Coast Ranges are the first thing they run into.