acid rain

Sulfur and nitrogen oxides do their damage not only in the form of airborne ozone and particulate, but in the form of acid rain, which threatens entire forest and aquatic ecosystems. Once emitted into the air, sulfur and nitrogen oxides form sulfates and nitrates, respectively, which are the principle components of acid rain. The victims to the impacts of acid rain are national treasures and forests.
Acid in rain, clouds and fog damage trees in two primary ways: (1) Directly damaging the needles and foliage, making them more vulnerable to adverse conditions including cold temperatures, and (2) Depleting nutrients from the soils in which the trees grow. Acid clouds and fog generally have even higher concentrations of damaging sulfates and nitrates than does acid rain. Thus, acid deposition is linked to the decline of red spruce growing at high elevations or in coastal areas which are immersed in acid clouds and fogs for long time periods.
Lake and stream ecosystems are also vulnerable to the effects of acid rain. As the acidity of the lakes and streams increases, the number of species that can live therein declines. It is not unusual to see episodic acidification of lakes and streams in the Great Lakes in which very few species can survive and nearly none can reproduce.
Moreover, acid rain in water causes an increase in aluminum concentrations, which is toxic to many fish species.
In 1990 Congress amended the Clean Air Act, calling for dramatic reductions in sulfur dioxide emissions to address the acid rain problem.
Despite the success of the acid rain program in reducing emissions of sulfur dioxide by about 25% thus far, eastern lakes have shown little or no improvement. Of 202 monitored lakes in Southeastern Canada, 67 percent have shown no improvement in acidity status. Moreover, forests at high elevations, while the stream water "can still pickle the leaves that fall from the trees" The reason for the program's failure to bring about the recovery of these ecosystems is simple, the program did not require deep enough cuts in SO2 or NOx.
What is Acid Rain
People make acid rain by putting pollutants in the air. Each day, automobiles exhaust pipes and chimneys from factories spew chemicals into the air. These chemicals become part of the rainwater in the clouds and form acids. When this acid rain falls, all the acids end up in our soil and in our lakes, rivers, and oceans.
When acid rain soaks into the ground, it dissolves valuable minerals in the soil and carries them away. Acid rain also damages tree leaves, slows plant growth, and changes the streams and lakes into which it falls. It destroys foods that fish eat and keep fish from hatching.
What is an Acid?
An acid is a chemical compound that tastes sour and will dissolve in water. An acid can irritate your skin and eyes. Some acids are so strong that they can actually dissolve rocks. The pH scale is used to describe the strength of an acid. This scale goes from 0, which means very acid, to 14, which means not acid at all.
What does acid rain do to trees and the environment?

The impact of acid rain on trees ranges from minimal to severe, depending on the region of the country and on intensity and type of air pollutant. Acid rain, acid fog and acid vapor damage the surfaces of leaves and needles, reduce a trees ability to withstand cold, and inhibit plant germination and reproduction. Consequently, tree vitality and regenerative capability are reduced.
When acid rain soaks into the ground, it dissolves valuable minerals in the soil. Acid rain also damages tree leaves, slow plant growth, changes streams and lakes into which it falls. It can also destroy foods that fish eat and keep fish eggs from hatching.
How does acid rain damage structures?

Many of the statues, bridges, and buildings in our cities are made of limestone. Limestone reacts with the chemicals in the acid rain by dissolving. After being exposed to acid rain year after year, these structures can become pitted, weakened and even destroyed.
How else does acid rain affect forests?
Prolonged exposure to acid rain causes forest soils to lose valuable nutrients. It also increases the concentration of aluminum in the soil, which interferes with the uptake of nutrients by the trees. Lack of nutrients causes trees to grow more slowly or to stop growing altogether.
More visible damage, such as defoliation, may show up later. Trees exposed to acid rain may also have more difficulty withstanding other stresses, such as drought, disease, insect pests and cold weather.
The ability of forests to withstand acidification depends on the ability of
the forest soils to neutralize the acids. This is determined by much the same geological conditions that affect the acidification of lakes.
Consequently, the threat to forests is largest in those areas where lakes are also seriously threatened – in central Ontario, southern Quebec, and the Atlantic provinces. These areas receive about twice the level of acid rain that forests can tolerate without long-term damage. Forests in upland areas may also experience damage from acid fog that often forms at higher elevations.
Are these effects reversible?
Acid rain induces irreversible changes to forest soils and their fertility in parts of Ontario, Quebec and the Atlantic provinces, as well as in the northeastern United States. For now, forests in affected areas where acid rain exceeds the critical loads are using the pool of minerals accumulated during pre industrial times although some monitoring sites are already deficient and visual damage has appeared. The loss of nutrients in forest soils may threaten the long-term sustain ability of forests in areas with sensitive soils.
What is an alkali?
An alkali is a chemical compound that is the opposite of an acid. By adding just the right amount of an alkali to an acid, it is possible for them to mix and become neutralized. This means the mixture is neither acid nor alkali.