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Acid deposition, more commonly known as “acid rain”,
results from the emission of sulfur dioxide and nitrogen oxide compounds
by a variety of sources, primarily from power plants in the Midwestern
United States, and from vehicles. These acidic compounds are blown by
westerly winds and fall back to earth as dry deposition in the form of
particles and gases, cloud and fog deposition, or as wet deposition in the
form of rain or snow. Acid deposition changes soil chemistry, impacting
forest vegetation and reducing the ability of soils to buffer acidic
inputs, and acidifies lakes and streams, detrimentally affecting aquatic
life.
The poor buffering
capability of the thin, acidic soils, and the nutrient-poor water bodies
in the Adirondack Park makes the lakes and ponds within the Park
particularly susceptible to acidification. Acid deposition leads to
decreased prey diversity and abundance. Loons adapt to decreased prey
availability by feeding prey items to chicks that are smaller or larger
than normally preferred. Adult loons on acidic lakes spend more time
feeding their chicks and have longer dive times. Chicks beg more
frequently than those on less acidic water bodies, and aquatic insects are
substituted for the primary prey instead of fish species. On rare
occasions, adult loons raising chicks on acidic water bodies have even
been observed flying to nearby lakes to capture fish and returning to the
natal lake with prey for the young, a very unusual behavior for Common
Loons.
Acid deposition also contributes to increased availability
of methylmercury in affected water bodies, leading to greater
bioaccumulation of methylmercury in the food chain. In the Adirondacks,
mercury levels in yellow perch and loons correspond to the acidity of the
water body on which they are captured; the animals with the highest tissue
mercury levels being captured on acidic water bodies.
The Clean Air Act
Amendments of 1970 and 1990 have resulted in lowered deposition of sulfur
dioxide, but have had negligible effect on the deposition of nitrogen
oxide compounds. The Adirondacks and other affected areas are now more
sensitive to acid deposition due to the accumulation of acids and loss of
buffering capacity in the soil. Computer models indicate that current
emission regulations are not sufficient to achieve full recovery of
sensitive ecosystems, and that further reductions in emissions of acidic
compounds are needed to realize and accelerate effective recovery of the
environment.
Recognition of
the need to decrease emissions causing acid deposition has manifested
through legislative and legal action. Several bills have been recently
introduced to Congress to achieve these goals. Legal action by the federal
government and several states, including New York, against power companies
failing to meet the requirements of the 1990 Clean Air Act Amendment has
resulted in settlements to reduce acidic emissions and to provide funding
of environmental projects. New York State recently set stricter emission
standards for vehicles sold in the state, and passed the Acid Rain
Pollution Credits Trading Bill, which prohibits New York utilities from
selling pollution credits to fourteen states upwind from New York. |
