Algae-eating nitrogen found in Lake Tahoe Basin

RENO - Like the mountains near Los Angeles, the Lake Tahoe Basin is a high-elevation environment downwind from urban areas with significant air pollution.

Because of Lake Tahoe's rapid decline in water clarity, researchers have spent the better part of the decade grappling with its environmental woes.

One issue has been the origin of air pollution - feeding algae-nourishing nitrogen into the lake - in the Tahoe Basin. Is it carried in the atmosphere from Sacramento and the Bay Area? Or is it generated in the basin itself?

It appears the nitrogen is generated in significant amounts both in the basin and outside it, says Alan Gertler, who heads the atmospheric sciences program at the University of Nevada, Reno.

Gertler, who also is a research professor at the Desert Research Institute, completed a preliminary study that sought to quantify which pollutants are the most significant atmospheric nitrogen sources for both the forest and lake in the Tahoe Basin.

Gertler was assisted by University of Nevada environmental science and health graduate student Leland Tarnay and researchers Robert R. Blank and George E. Taylor of George Mason University.

Tarnay gathered atmospheric samples of nitric acid and ammonia - the primary nitrogen species deposited in the lake - at D.L. Bliss State Park on the West Shore and the Incline Overlook on the East Shore.

"What Lee found was just during the summer months alone, the amount of nitric acid and ammonia that gets absorbed by the lake is equivalent to what others have estimated to go into the lake in the course of a whole year," Gertler says. "The bottom line seems to be that this gas-based stuff is pretty important ... and that more goes in during the summer than was previously thought."

Gertler says more atmospheric studies are needed. "We need to look at the transport of air that comes into the basin versus that which stays," he said.