Acid Rain is a type of air pollution, formed when oxides of sulfur and nitrogen combine with atmosphere moisture to yield sulfuric and nitric acids, which may then be carried long distances from a source before they are deposited by rain. This pollution may also be snow, fog, or a dry form of precipitation. Acid rain is currently a subject of great controversy because of widespread environmental damage for which it has been blamed, including eroding structures, injuring crops and forests, and threatening or killing life in freshwater lakes.
The Effect Of Acid Rain
When the environment can't neutralize the acid rain, damage will occur to forests, crops, lakes, and fish. Toxic metals such as copper and lead can also be leached from water pipes into drinking water.
Research published in 1996 suggested that forests and forest soils are more susceptible to the effects of acid rain than previously believed, and recovery from these effects is very slow. In light of this information, many scientists believe that the 1990 amendments to the Clean Air Act will not be sufficient to protect lakes and forest soils of the northeastern United States from further acidification.
Effects In The Aquatic Ecosystems
The interactions between living organisms and the chemistry of their aquatic habitats are extremely complex. If the number of one species or group of species changes in response to acidification, then the ecosystem of the entire water body is likely to be affected through the predator-prey relationships of the food web. At first, the effects of acid deposition may be almost imperceptible, but as acidity increases, more and more species of plants and animals decline or disappear.
As the water pH approaches 6.0, crustaceans, insects, and some plankton species begin to disappear.
As pH approaches 5.0, major changes in the makeup of the plankton community occur, less desirable species of mosses and plankton may begin to invade, and the progressive loss of some fish populations is likely, with the more highly valued species being generally the least tolerant of acidity.
Below pH of 5.0, the water is largely devoid of fish, the bottom is covered with undecayed material, and the near-shore areas may be dominated by mosses.
Terrestrial animals dependent on aquatic ecosystems are also affected. Waterfowl, for example, depend on aquatic organisms for nourishment and nutrients. As these food sources are reduced or eliminated, the quality of habitat declines and the reproductive success of the birds is affected.
Affects Of Terrestrial Plant Life
Both natural vegetation and crops can be affected from acid rain:
- It can alter the protective waxy surface of leaves, lowering disease resistance.
- It may inhibit plant germination and reproduction.
- It accelerates soil weathering and removal of nutrients.
- It makes some toxic elements, such as aluminum, more soluble. High aluminum concentrations in soil can prevent the uptake and use of nutrients by plants.
Affects of Animal Life
The effects on terrestrial wildlife are hard to assess. As a result of pollution-induced alteration of habitat or food resources, acid deposition may cause population to decline through stress (because of decreases in available resources) and lower reproductive success.
We eat food, drink water, and breathe air that has come in contact with acid deposition.
Canadian and U.S. studies indicate that there is a link between this pollution and respirator problems in sensitive populations such as children and asthmatics.
Acid deposition can increase the levels of toxic metals such as aluminum, copper, and mercury in untreated drinking water supplies.
Is Acid Deposition Occurring To The Same Extent Across Canada?
No. Sulphur emissions tend to be concentrated in relatively few locations, while the sources of nitrogen emissions are widely distributed; however, where they are deposited depends on more than just where they are produced. Airborne acidic pollutants are often transported by large scale weather systems thousands of kilometers from their point of origin before being deposited. In eastern North America, weather systems generally travel from southwest to northeast. Thus, pollutants emitted from sources in the industrial heartland of the midwestern states and central Canada regularly fall on the more rural and comparatively pristine areas of the northeastern U.S. and southeastern Canada.
Did you know?
- That about 40% of nitrogen oxides come from transportation (cars, trucks, buses,trains), about 25% from thermoelectric generating stations, and the balance from other industrial, commercial, and residential combustion processes.
- That more than 80% of all Canadians live in areas with high acid rain-relatedpollution levels.
- That it has been estimated that about 50% of the sulphate deposited in Canada is derived from sources in the U.S.