| Significant anthropogenic perturbations of the nitrogen cycle are the result of rapid
population growth, with mounting need for food and energy production. The increase of
reactive nitrogen compounds (such as NOx, HNO3, NH3, and N2O) has a significant impact
on human health, environment, and climate. NOx emissions contribute to O3 chemistry,
aerosol formation and acidic precipitation. Ammonia is a notable atmospheric pollutant that
may deteriorate ecosystems and contribute to respiratory problems. It reacts with acidic gases
to form aerosols or is deposited back to ecosystems. The application of fertilizers accounts
for most of the N2O production, adding to greenhouse gas emissions. We analyze the change
of some reactive nitrogen compounds based on observations, in eastern United States. Results
show that the control of NOx and SO2 emissions over the last decades caused a
significant decrease of acidic deposition. The nitrate deposition is highest in eastern US,
while the ammonium ion concentration is highest in central US regions. Overall, the
inorganic nitrogen wet deposition from nitrate and ammonium is enhanced in central,
and eastern US. Research shows that sensitive ecosystems in northeastern regions
exhibit a slow recovery from the accumulated effects of acidic deposition. Given
the growing demand for nitrogen in agriculture and industry, we discuss possible
pathways to reduce the impact of excess reactive nitrogen on the environment. |