Industries Pollute Faraway Rain and Snow

Rain and snow falling in the Northeast and Midwest can also bring with them nitrates carried from pollution sources hundred of miles away, according to new research from the U.S. Geological Survey (USGS).

Most of the nitrates found in precipitation in those parts of the country come from coal-burning power plants and other industrial facilities far away, rather than from local vehicle traffic, the study found. Nitrates in rain and snow can contribute to acid rain, cause local streams and soils to become too acidic and hurt forests and coastal water quality, according to the USGS.

While gasoline-burning vehicles emit the most nitrogen oxides in the Northeast and Midwest, the nitrates from faraway sources might contribute more to pollutants in rain and snow, the study reported. Because power plants and other industrial sources send their emissions high into the air, their pollutants can travel much farther before falling to the surface. Cars and trucks, on the other hand, tend to deposit their pollutants over shorter distances near the areas where they're actually traveling.

"These results demonstrate that we have a new chemical analysis tool for tracing the influence of emissions from stationary sources," said Emily Elliot, assistant professor at the University of Pittsburgh and a former USGS scientist. "This could be a powerful method for monitoring the effects of stationary source emission reductions slated for this region over the next eight years."

The USGS study, published in the journal "Environmental Science and Technology," is the first large-scale examination of nitrogen isotopes in rain and snow. Researchers measured levels of nitrogen isotopes in samples taken from 33 different monitoring sites operated by the National Atmospheric Deposition Program (NADP). The NADP measures pollution levels in precipitation at 250-plus stations around the country, most of them in rural areas to eliminate city-origin pollution.

While distant power plants and other industrial sources seem to contribute significant amounts of precipitation-borne nitrates, pollution from vehicles shouldn't be discounted when considering local environmental impacts of pollution, the researchers cautioned.

"Our results highlight the need to improve our understanding of the fate of vehicle emissions," Elliott said. "One way we can do this is by expanding monitoring networks to include more urban sites."

Developing better ways of tracking the sources of nitrogen pollution is important to help develop improved environmental regulations and pollution-reduction strategies, according to the USGS. The USGS's nitrate precipitation research was support by the New York State Energy Research and Development Authority and the Electric Power Research Institute.

U.S. Geological Survey, "USGS Study Identifies Major Source of Nitrate in Precipitation." URL:(http://www.usgs.gov/newsroom/article.asp?ID=1809&from=rss)