Tests fail to identify cause of nitrogen in local lakes | AspenTimes.com
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Tests fail to identify cause of nitrogen in local lakes

Jeremy Heiman

A high concentration of nitrogen in Capitol Lake is causing concern among wildlife officials, but initial tests have failed to identify the source of the pollution.

Capitol is one of five high-mountain lakes included in a nitrogen study by the U.S. Forest Service and the U.S. Geological Survey. The lakes have unusually high quantities of nitrogen compounds. The other lakes are Avalanche and Moon in the Maroon Bells Snowmass Wilderness, and Brooklyn and Tabor in the Collegiate Peaks Wilderness.

Preliminary data gathered last spring is inconclusive, said Andrea Holland-Sears, a Forest Service hydrologist. Because pollutants can be scrubbed out of the air by snow, and are often concentrated in the snowpack, scientists from the U.S. Geological Survey analyzed snow in the Aspen area. But little in the way of nitrogen compounds was found.

They found that no more nitrates were deposited in snow near Aspen than in the more remote area of Sunlight Peak, or elsewhere in the Rockies. Another federal program, the National Acidic Deposition Program, monitors several kinds of air pollution on Sunlight Peak.

Sources of airborne nitrogen compounds, such as automobiles, snowmobiles and agricultural fertilizers, do not appear to be the source, Holland-Sears said.

“At this point,” she said, “it doesn’t look like there’s any local contribution to nitrogen in the lakes.”

But, because data was gathered from the snowpack of the 1999-2000 winter, when snow was low, the conclusion drawn from the tests is not as conclusive as it might have been in another year, Holland-Sears said.

Moreover, the finding leaves unanswered the study’s original questions, intended to determine why the nitrogen is concentrated in the lakes, and where it comes from, she said.

The Forest Service is concerned about the level of nitrogen contamination because the agency is charged with protection of its resources. Agency scientists want to find out if the nitrogen problem is human-caused, Holland-Sears said.

“Our concern is we have these wilderness lakes that are supposed to be `untrammeled by man,’ ” she said. “That’s in the Wilderness Act.”

Nitrates function as a fertilizer. Unnatural concentrations of nitrogen contribute to the growth of algae and other aquatic plants and can cause imbalances in aquatic ecosystems.

This problem is made worse by the length of high country winters. With alpine lakes under ice for as long as eight to 10 months, the algae dies. As it decomposes, it takes available oxygen from the water, killing both fish and the insect larvae they eat.

Forest Service measurements of nitrogen compounds in the lakes go back only to 1991. Nitrogen levels are neither increasing nor decreasing, Holland-Sears said, but the levels are higher than would normally be expected.

Holland-Sears said the Forest Service and Geological Survey will look at geological sources of nitrogen next. Nitrogen compounds can leach out of rock and soil with rainwater and spring runoff, concentrating in lakes.

A study of the snowpack was done before geological sources were examined, she said, because the snowpack study is easier and less expensive.

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