Precipitation in Northeast, Midwest Contains Nitrate from Distant Industrial Facilities
Rain and snow in rural areas of the Northeastern and Midwestern
United States contain nitrate that has been traced to power plants and
other industrial facilities hundreds of miles away, according to a new
U.S. Geological Survey (USGS) study.
Although vehicles are the single largest emission source of nitrogen
oxides in the Northeast and Midwest, distant stationary sources may
have a greater impact on nitrate found in rain and snow, USGS officials
stated.
"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 eight
years," said Emily Elliott, former USGS scientist and current assistant
professor at the University of Pittsburgh.
The study, published recently on the Web site of the journal Environmental Science & Technology,
is 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.
"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," Elliott said.
The abstract of the Environmental Science & Technology article can be accessed at http://pubs.acs.org/journals/esthag/index.html, under the "Articles ASAP" tab.