Ammonia emissions have become a serious concern for
scientists at Harvard University. Of particular note, thirty eight U.S.
national parks are experiencing “accidental fertilization” at or above a
critical threshold for ecological damage according the study recently published
in Atmospheric Chemistry and Physics.
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The environmental
scientists, experts in air quality, atmospheric chemistry, and ecology, have
been studying the fate of nitrogen-based compounds that are blown into natural
areas from power plants, automobile exhaust, and—increasingly—industrial
agriculture. Nitrogen that finds its way into natural ecosystems can disrupt
the cycling of nutrients in soil, promote algal overgrowth and lower the pH of
water in aquatic environments, and ultimately decrease the number of species
that can survive.
“The vast
majority, 85 percent, of nitrogen deposition originates with human activities,” explains principal investigator Daniel J. Jacob, Vasco
McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering
at the Harvard School of Engineering and Applied Sciences (SEAS). “It is fully
within our power as a nation to reduce our impact.”
Existing air
quality regulations and trends in clean energy technology are expected to
reduce the amount of harmful nitrogen oxides (NOx) emitted by coal
plants and cars over time. However, no government regulations currently limit
the amount of ammonia (NH3) that enters the atmosphere through
agricultural fertilization or manure from animal husbandry, which are now
responsible for one-third of the anthropogenic nitrogen carried on air currents
and deposited on land.
“Ammonia’s pretty
volatile,” says Jacob. “When we apply fertilizer in the United States, only
about 10 percent of the nitrogen makes it into the food. All the rest escapes,
and most of it escapes through the atmosphere.”
The team of
scientists—comprising researchers from Harvard SEAS, the National Park
Service, the USDA Forest Service,
the U.S. Environmental Protection Agency, and
the University of California, Irvine—presents evidence that unchecked increases
in nitrogen deposition are already threatening the ecology of federally
protected natural areas.
In many previous
studies, environmental scientists have identified the nitrogen levels that
would be ecologically harmful in various settings. The new Harvard-led study
uses a high-resolution atmospheric model called GEOS-Chem to
calculate nitrogen deposition rates across the contiguous United States, and
compares those rates to the critical loads.
The findings
suggest that many parks may already be suffering.
Read
more at Harvard
School of Engineering and Applied Sciences.
Sol
Duc falls trail, Olympic national park, WA image via Shutterstock.