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Study: Sierra Nevada Lakes Benefit From Clean Air Law

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Lakes in the Sierra Nevada have been getting cleaner for almost 45 years | Photo: Greater Southwestern Exploration Company/Flickr/Creative Commons License

The nation's air quality laws seem to be working, at least when it comes to lakes in the Sierra Nevada. According to a recent study by researchers at UC Riverside, lakes in the state's largest mountain range have gradually become less affected by acid rain since 1970 -- about when the first Clean Air Act was passed.

According to the Environmental Protection Agency, lakes in the Sierra Nevada are among the nation's most vulnerable to damage from acid rain. That's in part due to California's geography: the Sierra Nevada captures industrial air pollution from cities on the coast and in the Central Valley, which falls on the range as a contaminant in rain.

But according to a long-term study by UC Riverside environmental scientist James O. Sickman, the years since 1970 have seen less pollution raining down on the mountain lakes, which means cleaner water for fish and wildlife -- and for people downstream.

In the study, which began in 1980, Sickman and his colleagues took samples of lakebed sediments from remote Sierra Nevada lakes accessible only on foot, where any pollutants in the sediments are likely to have gotten there by air rather than runoff from highways or other developments.

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Sickman and his colleagues hiked to the lakes, then rafted to the center of each lake where lake bottom sediments would be thickest. They took core samples of those sediments, which were then analyzed for age and chemical composition.

The results: since 1970, the amount of soot, sulfur, and nitrogen hitting the lake water has been dropping year by year. In a press statement issued by UC Riverside, Sickman and his colleague Andrea Heard, who analyzed many of the core samples, attribute that lowering pollution to emission standards set by the Clean Air Act in 1970. Those standards included emissions of sulfur dioxide and nitrogen oxides, two major components of acid rain.

Among the beneficiaries of the lakes' slow recovery have been native invertebrates, including clams and freshwater sponges, whose calcium carbonate exoskeletons are vulnerable to being dissolved by lake water that's too far toward the acid end of the scale.

"The Clean Air Act is arguably the most important and successful environmental law in the United States, both from a human health standpoint and the environment," said Sickman.

Along with Heard and Sickman, the core sample studies were done by Delores M. Lucero of UC Riverside; Danuta M. Bennett and Peter Homyak of UC Santa Barbara, Neil L. Rose and John M. Melack at University College London, Jason H. Curtis at the University of Florida, and William Vicars at the University of Colorado.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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