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Signs of recovery from acid rain damage


October 18, 1999
Web posted at: 12:27 p.m. EDT (1627 GMT)

Lakes and streams in North America and Europe are beginning to recover from the damage inflicted by acid rain, scientists report.

The recovery is being attributed to the passage and enforcement of environmental regulations and international agreements that reduce the emissions that produce acid rain.

Emissions from burning fossil fuels steadily increased from the beginning of the Industrial Revolution in the 18th century until the 1970s. The sulfur and nitrates released into the atmosphere eventually return to the Earth as acid rain. This study provides the first conclusive evidence that international and regional agreements designed to reduce the emissions that cause acid rain, beginning with the United Nations' First Sulphur Protocol in 1985, are working.

Sulfur dioxide concentrations in north/central Europe air decreased by 63 percent between 1985 and 1996, according to the report. Sulfur dioxide is converted in the atmosphere to sulfuric acid, the main ingredient that produces acid rain. The United States and Canada experienced a 28 percent decline in the same emissions between 1980 and 1995. In Great Britain, emissions of sulfur also decreased by 32 percent between 1979 and 1993.

To determine whether emission regulations impacted the recovery of lakes and streams that had suffered from years of acid rain, scientists collected data from 205 lakes and streams from five regions in North America and three in Northern Europe. John L. Stoddard, a scientist with the Environmental Protection Agency, and colleagues then studied two components of acid rain - sulfate and nitrate.

The study found significant declines of one to six percent per year in sulfate levels in many lakes and streams in the 1990s, resulting in recovery for some waters and expected recovery in others. Recovery is defined as the return to pre-industrial levels of acidity and other components that counteract acidity. Great Britain was the only region that did not show a decrease in sulfate concentrations.

Reduced emissions don't automatically translate to immediate improvement in streams, lakes and rivers, though.

In Maine, for example, some waters continued to acidify even though sulfuric acid concentrations in rain decreased. The scientists concluded that several factors contributed to continued lake acidity: variations in climate; increasing levels of nitrogen compounds, such as nitric acid, in precipitation; declines in the ability of a watershed to neutralize acid and the short length of time data has been collected.

Recovery in alkalinity, expected in regions where sulfate concentrations declined significantly, was observed in all three regions of Europe, especially in the 1990s. Alkalinity is a marker for the ability a body of water had to resist damage from acid rain. Only the Vermont/Quebec region of North America showed a reduction in alkalinity. The scientists speculate that it is possible that the supply of acid neutralizing chemicals in rocks and soils in the other Northern Hemisphere regions has been depleted by decades of acid rain.

The study, titled "Regional trends in aquatic recovery from acidification in North America and Europe 1980-1995," was published in the journal Nature.. The research was conducted under the auspices of the United States Environmental Protection Agency.

Copyright 1999, Environmental News Network, All Rights Reserved

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