USGS Study Identifies Major Source of Nitrate in Precipitation

Monday October 22nd 2007
Filed Under USGS 



Nitrate found in precipitation occurring in rural areas of the
Northeastern and Midwestern United States is primarily caused by
emissions from stationary sources located hundreds of miles away,
according to a new U.S. Geological Survey (USGS) study.

Stationary sources include coal-burning power plants and other
industrial facilities. Although vehicles are the single largest emission
source of nitrogen oxides in this region, distant stationary sources may
have a greater impact on nitrate found in rain and snow.

“These results demonstrate that we have a new chemical analysis tool for
tracing the influence of emissions from stationary sources. This could
be a powerful method for monitoring the effects of stationary source
emission reductions slated for this region over the next 8 years,” says
Emily Elliott, former USGS scientist and current assistant professor at
the University of Pittsburgh.

The study, published in the journal Environmental Science and
Technology, presents the first large-scale investigation of nitrogen
isotopes in precipitation.  The authors analyzed stable nitrogen
isotopes at 33 long-term National Atmospheric Deposition Program (NADP)
monitoring sites. The NADP is a cooperative nationwide program that
measures air pollutant concentrations in rain and snow at more than 250
stations across the United States, most of which are deliberately
located in relatively rural settings away from urban, industrial or
agricultural centers.

Nitrogen oxides originate from the burning of fossil fuels, including
emissions from motor vehicles, electric utilities and other sources.
Power plants and other stationary sources emit pollutants high in the
atmosphere that can be transported for long distances before falling to
the ground, while vehicles emit pollutants through tail pipes close to
the ground where they are more likely to be deposited over shorter
distances near roadways.  Further, a portion of emissions from all
sources may be deposited on the landscape in gaseous forms such as
aerosols and particles in addition to precipitation.  Thus the authors
urge caution when interpreting their results, stating that both
stationary sources and vehicles are important contributors to air
pollution throughout the region.  “Our results highlight the need to
improve our understanding of the fate of vehicle emissions; one way we
can do this is by expanding monitoring networks to include more urban
sites,” says Elliott.

Nitrogen oxides in the atmosphere are a primary societal concern, given
their contributions to a wide variety of environmental and health
impacts. Nitrate is an important contributor to acid rain and can result
in acidification of streams and soils, forest decline and coastal water
degradation.  Determining the fate of major sources of nitrogen
emissions is necessary to develop sound regulatory and mitigation
strategies.

The research was supported by the New York State Energy Research and
Development Authority (www.nyserda.org/programs/Environment/EMEP/) and
the Electric Power Research Institute.

The abstract of the ES&T article is available on-line at
http://pubs.acs.org/journals/esthag/index.html, under the Articles ASAP
tab. Full text for the ES&T article can be obtained from Michael
Bernstein, Office of Communications, American Chemical Society,
(202)-872-6042 (m_bernstein@acs.org).

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