Nitrogen derived from human activities has polluted lakes throughout the
Northern Hemisphere for more than a century and the fingerprint of
these changes is evident even in remote lakes located thousands of miles
from the nearest city, industrial area or farm.
The findings, published in the journal Science Dec. 16, are
based on historical changes in the chemical composition of bottom
deposits in 36 lakes using an approach similar to aquatic archeology.
More than three quarters of the lakes, ranging from the U.S. Rocky
Mountains to northern Europe, showed a distinctive signal of nitrogen
released from human activities before the start of the 20th
century, said Gordon Holtgrieve, a postdoctoral researcher at University
of Washington School of Aquatic and Fishery Sciences and lead author of
the report. The UW and a dozen other research institutions contributed
to the research.
"When it comes to nitrogen associated with humans, most studies have
focused on local and regional effects of pollution and have missed the
planetary scale changes," Holtgrieve said. "Our study is the first
large-scale synthesis to demonstrate that biologically-active nitrogen
associated with human society is being transported in the atmosphere to
the most remote ecosystems on the planet."
Burning fossil fuel and using agricultural fertilizers are two key
ways humans increase the amount of nitrogen entering the atmosphere.
Once in the atmosphere, this nitrogen is distributed by atmospheric
currents before being deposited back on Earth in rain and snow, often
thousands of miles from the source.
No comments:
Post a Comment