U.S. Clean Air Act successful in Greenland ice cap
The samples collected from the Greenland ice sheet show that the US Clean Air Act had played an important role in changing the conditions of the Earth's atmosphere.
The atmospheric scientists at University of Washington studied the samples and found a link between air acidity and nitrogen preservation in snow.
The research team was trying to study smog and it discovered a link in the geologic record between smog and acid rain. The US Clean Air Act was passed in 1970 following rising air pollution and incidences of acid rain.
This Act makes it mandatory for coal power plants and other polluters to stop using sulfur.
"How much the nitrate concentrations in ice core records can tell about NOx and the chemistry in the past atmosphere is a longstanding question in the ice-core community," said Lei Geng, a University of Washington researcher in atmospheric sciences, and lead author of the new research published in Proceedings of the National Academy of Sciences.
Earlier research by co-author Eric Steig, a UW professor of Earth and space sciences, suggested that comparing amounts of the two stable forms of nitrogen - nitrogen-15 and nitrogen-14 - in nitrate could help in finding out the emission sources of NOx.
"The isotope records really closely follow the atmospheric acidity trends," said co-author Becky Alexander, a UW associate professor of atmospheric sciences. "You can really see the effect of the Clean Air Act in 1970, which had the most dramatic impact on emission of acid from coal-fired power plants."