Tahoe gridlock pollutes the lake, scientists believe | TahoeDailyTribune.com

Tahoe gridlock pollutes the lake, scientists believe

Dan Thrift / Tahoe Daily Tribune / Periods of heavy traffic have impacted lake clarity, scientists say.

Air pollution from Asia’s coal-powered energy plants and dust storms in the Gobi Desert could be a minor factor in Lake Tahoe’s declining clarity.

But scientists believe a majority of air pollution affecting Lake Tahoe comes straight from rush-hour traffic here in the Lake Tahoe Basin.

Air pollution’s effect on the lake came up at a meeting between California’s air and water quality control boards, which came together for the first time this month to discuss how their mandates overlap.

The California Air Quality Control Board is primarily concerned with health problems like asthma in children, while the Water Board is responsible for regulating water quality for impacts to wildlife, safe drinking water or clarity standards at Lake Tahoe. The meeting is the first sign they may soon work together to address areas where air and water pollution impact each other.

It’s been known for several years that air pollution affects the lake, but scientists are still figuring out where that pollution comes from, according to Dave Roberts with Lahontan Water Board.

More than half of the nitrogen feeding algae growth in the lake comes from air pollution. But what’s unknown is how, when and where the nitrogen got into the air. Much of it is nitrous oxide, which comes out of tailpipes.

“It’s been documented more and more that what’s coming from the sky is significant and problematic,” Roberts said. “It’s certainly going to be gaining attention in the next couple of years.”

Another problem is fine sediment, which is dirt that is so small it literally takes forever to sink to the bottom of Lake Tahoe. While a lot of it comes from stream bank erosion, studies are showing road dust is turning out to be a significant factor, Roberts said.

Periods of rush hour traffic in Lake Tahoe correspond to the largest peaks in pollution in their detection instruments.

The impact of Sacramento’s smog is also under debate. Monitoring systems on the West Slope have shown the smog usually is contained in the Central Valley. Storms from the West can bring more of it into the Tahoe basin, though.

The San Francisco Bay is a classic example of air impacting water: almost 60 pounds of mercury enter the bay each year from the air. The metal gets into the air in vapor form through coal-fired power plants.

Exposure to mercury can cause damage to the central nervous system, especially in developing fetuses, according to the U.S. Environmental Protection Agency.

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