Recovery from acid rain speeding up in Northeast lakes
Strock KE, SJ Nelson, JS Kahl, JE Saros, WH McDowell. 2014. Decadal trends reveal recent acceleration in the rate of recovery from acidification in the Northeastern U.S. Environmental Science and Technology. dx.doi.org/10.1021/es404772n
Lakes in the U.S. Northeast are recovering from acid rain faster now than in the past, according to a new study.
In many parts of the world, lakes turned more acidic beginning in the 1970s due to sulfur dioxide and nitrogen oxides emitted by power plants, factories and vehicles. In upstate New York and New England, some lakes have been recovering very slowly or not at all, even though acid rain has declined.
Acid rain can kill fish and other aquatic life, deplete forest soils of nutrients and increase toxic metals, such as aluminum and mercury, in lakes and streams.
For the new study, researchers analyzed 43 sites in New York’s Adirondack Mountains and 31 sites in New England. Sulfate concentrations, which are a measure of acidity, declined at a rate nearly three times faster between 2002 and 2010 than during the 1980s and 1990s. Nitrates, which also acidify, showed a decline for the first time after 2000.
Total emissions of sulfur and nitrogen in the United States decreased by 51 and 43 percent between 2000 and 2010 after regulations targeted vehicle exhaust and power plant emissions.
“The results suggest a recent acceleration in recovery, but continued monitoring is warranted,” wrote the study authors from the University of New Hampshire and University of Maine in the journal Environmental Science & Technology.
However, pH levels have remained variable. They have increased, or become less acidic, in some lakes, but decreased or remained the same in others.
One reason for the slow and uneven recovery is that soils in the region continued to become more acidic in the early 2000s even as pollution levels dropped, the researchers said. Some variability could be due to human development, such as use of road salts, along those lakes, the study authors said.
An increase in extreme precipitation events could be increasing runoff into lakes and streams. Climate-related changes in soil moisture also might alter how much sulfur in forest soils flows into waterways, wrote the authors.