11 June 2009 New evidence on disruption of nitrogen cycle
Scientists are getting a better grip on the nitrogen cycle. They
are learning about sources of nitrogen and how this element
changes as it loops from the nonliving to the living. Scientists
have determined humans are disrupting the nitrogen cycle by
altering the amount of nitrogen stored in the biosphere. The
chief culprit is fossil fuel combustion, which releases nitric
oxides into the air that combine with other elements to form
smog and acid rain. However, it has been difficult to know
precisely the extent to which such emissions have altered the
nitrogen balance. Researchers from Brown University and the
University of Washington have found a new way to make the link.
The scientists show that comparing nitrogen isotopes in their
deposited form, nitrates, can reveal the sources of atmospheric
nitric oxide. In a recently published paper in Science, the
group traces the source of nitrates to nitric oxides released
through fossil fuel burning that paral