N. American and European Streams Show Signs of Recovery from Acid
Rain Damage
10/18/99
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RELAYED TEXT STARTS HERE:
Title: Signs of Recovery from Acid Rain Damage
Source: Environmental News Network
Status: Copyright 1999, contact source for permission to reprint
Date: October 18, 1999
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.