PITTSBURGH, Oct. 24 (UPI) -- A U.S. study suggests nitrogen oxides produced by burning fossil fuels might pollute urban water supplies and roadside waterways more than thought.

   A three-year study led by University of Pittsburgh Professor Emily Elliott recommends urban areas and roadways be specifically monitored for nitrogen deposition. Nitrate, which forms when exhaust from vehicles and smokestacks oxidizes in the atmosphere, can result in stream and soil acidification and a variety of health maladies.

   Elliott and colleagues conducted the first large-scale application of a method for determining the source of atmospheric nitrate at 33 precipitation collection sites across the Midwestern and Northeastern United States.

   The researchers determined the primary sources of nitrates were stationary sources, such as power plants and factories, located hundreds of miles away. Vehicle exhaust is more likely deposited over shorter distances near roadways.

   Elliott said future research will further characterize the isotopic ratios of nitrogen oxides from various sources and quantify how the values change with different emission controls.

   The study -- which involved scientists from U.S. Geological Survey, the University of California-Berkeley, Cornell University and the Institute of Ecosystem Studies in New York -- is reported in the online edition of the journal Environmental Science and Technology.
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