Bad air from California may cause algae in Lake Tahoe

Tuesday, Nov. 14, 2000 | 10:23 a.m.

Since 1997, DRI has collected air samples at four sites ringing the lake. Researchers are testing for the presence of gaseous nitrogen compounds, byproducts of auto emissions they suspect may play an important role in fueling the algae growth stealing Lake Tahoe's famed clarity.

"It appears as if they might be underestimating the nitrogen contribution" from elsewhere, Alan Gertler, an atmospheric sciences researcher at DRI, told the Reno Gazette-Journal.

It's long been known that nitrogen is one of the main pollutants responsible for Tahoe's problems. Another is phosphorus, commonly found in sediment washing into the lake by streams and from road cuts. Both act as nutrients for algae growing in Tahoe's waters.

What's unknown is how much of Tahoe's nitrogen-related woes are caused by smog-belching cars driving within the Tahoe Basin as opposed to pollution blowing to the area during the summer from busy urban areas to the west.

Gertler and colleagues tried to answer the question by sampling for nitric acid and ammonia - gaseous nitrogen compounds never looked for before at the lake. Elevated levels of nitric acid in particular appear to be blowing into the basin from elsewhere, indicating distant air pollution may be a significant factor, Gertler said.

While transportation patterns inside the Tahoe Basin can be regulated and erosion control projects can help reduce the influx of phosphorus, controlling air pollution from far away could prove particularly difficult if not impossible.

"That's probably the worst scenario to try and control," Gertler said. "It means you're out of luck."

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