One Earth, One Future Our Changing Global Environment (1990) / Chapter Skim
Currently Skimming:
11. Lakes, Forests, and Acid Deposition
11. Lakes, Forests, and Acid Deposition
Pages 131-144
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 131... ...
In addition, it has become a key suspect in the declining health of some species of forest trees in North America and Europe. Acid deposition results when pollutants, particularly oxides of nitrogen and sulfur, are emitted from smokestacks, smelters, and automobile exhausts into the atmosphere.
|
From page 132... ...
China, which is embarking on ambitious plans for industrial development, will build factories and power plants drawing on that country's large reserves of high sulfur coal. Coal that contains high concentrations of sulfur is also burned elsewhere in the world, such as in some Eastern European countries.
|
From page 133... ...
Since then, scientists have conducted millions of measurements and produced thousands of publications to understand the causes and consequences of acid deposition. THE ACIDIFICATION PROCESS Nearly all of the acidification causing environmental damage comes from sulfur dioxide (SO2)
|
From page 134... ...
Scientists have determined that in soils receiving doses of acid deposition, the excess hydrogen ions displace other elements, including nutrients such as potassium, magnesium, and calcium, and retard plant growth. High concentrations of hydrogen also release aluminum, a metal naturally occurring in soil.
|
From page 135... ...
Surveys reveal that in Canada, half of the 700,000 lakes in the six eastern provinces are extremely sensitive to acid deposition. So are large stretches of Canada's western anct northwestern provinces, as well as much of northern Europe and vast expanses of Asia, Africa, and South America.
|
From page 136... ...
Much of the understanding about the effects of acid deposition on lake ecosystems has been obtained from studies in laboratories and artificial acidification of experimental lakes. Lakes in or near populated areas may be affected by numerous chemical pollutants from a variety of sources including recreational uses, agriculture, and nearby mining.
|
From page 137... ...
After ~ years, the trout the top of the food chain in the lake were no longer reproducing, and their mortality rates had gone up considerably. Scientists believe that the number of species in a lake declines continuously with increasing acidity below pH values of 6.5 to 7.0 and that many species that are foraged by fish higher in the food chain are lost at pH values near 6.0.
|
From page 138... ...
In the late 1970s, extensive discoloration of needles and declining rates of growth in forests in northeastern Bavaria in the Federal Republic of Germany suggested to scientists that acid deposition, and the ground-level ozone producecl by the chemical reactions involved in acid deposition, play a major role in what has come to be known as "forest dieback" or, in German, waZd:ersterben (forest death)
|
From page 139... ...
(Photo taken ~ 1987 by Y ~ US Forest sliced
|
From page 140... ...
Red spruce that grows at high elevations of the northern Appalachians in the eastern United States has drawn special attention because analyses of tree rings reveal that in the past quarter century, the growth rate of the trees has declined substantially and over half of the mature red spruce trees in the high elevations of the Adirondack and Green mountains have died. In New York, Vermont, and New Hampshire, stands of red spruce began to decline between the late 1950s and mid-1960s.
|
From page 141... ...
Emissions from Mexico's refineries are corroding Mayan artifacts. In southwestern Colorado, air pollutants from several power plants and a nearby smelter are suspected in the quickening deterioration of ancient sandstone cities of the Ansazi Indians Of course, factors other than acid deposition contribute to aging and deterioration of materials, including sunlight, wind, and water.
|
From page 142... ...
Progress has been made over the last 15 years. In the northeastern United States, the sulfate content of rain and the concentration of sulfur compounds in the air have decreased, reflecting pollution control measures mandated by the 1970 Clean Air Act and efforts of individual states to limit emissions.
|
From page 143... ...
Fuel switching may displace coal miners; coal cleaning techniques typically remove only 10 to 30 percent of the sulfur; anc! conventional flue-gas desulfurization is expensive and reduces the efficiency of the plant.
|
From page 144... ...
Meanwhile, limestone is mixect with coal in the combustion process and efficiently captures sulfur ctioxide. Such techniques are improving and eventually could yield very large reductions in the emissions responsible for acid deposition.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.