Acid Rain

Acid rain is the mixture of wet and dry decomposition (decomposed material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. The precursors, or chemical forerunners of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide(S02) and nitrogen oxides(N0x) resulting from fossil fuel combustion.
In Nigeria roughly 95% of all the S02 and N0x comes from the electric power generators and automobiles that relies on burning fossil fuel like coal, petrol and deseil. This statistics does not apply to the Niger Delta region of the country.
Researchers (Nduka JK et al) from the pure and Industrial Chemistry Department, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria collected rain samples from Warri and Port Harcourt, two major oil-producing cities in Nigeria in April-June, July-August, and September-October 2005 and 2006. Awka a ‘‘non-oil’’ city was used as control. Results showed that the rain samples were acidic. That the pH values for the 2years under study show that the rainfall in Warri was more acidic than that in Port Harcourt. Oil exploration and other anthropogenic sources may be responsible for the Acid rain in Port Harcourt and Warri.
Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. The result is a mild solution of sulfuric acids and nitric acid. When sulfur dioxide and nitrogen oxide are released from power plant, automobile and other sources, prevailing winds blow these compounds across state and national borders, sometimes over hundreds of miles.
NOTE: Combustion of fuels creates sulfur dioxide and nitric oxides, they are converted into sulfuric acid and nitric acid.
Adverse effects
Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing insect and aquatic life-forms as well as causing damage to buildings and having impacts on human health.
Surface waters and aquatic animals
Both the lower pH and higher aluminium concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals. At pHs lower than 5 most fish eggs will not hatch and lower pHs can kill adult fish. As lakes and rivers become more acidic biodiversity is reduced. Acid rain has eliminated insect life and some fish species, including the brook trout in some lakes, streams, and creeks in geographically sensitive areas. The United States Environmental Protection Agency's (EPA) website states: "Of the lakes and streams surveyed, acid rain caused acidity in 75 percent of the acidic lakes and about 50 percent of the acidic streams"
Soils
Soil biology and chemistry can be seriously damaged by acid rain. Some microbes are unable to tolerate changes to low pHs and are killed. The enzymes of these microbes are denatured (changed in shape so they no longer function) by the acid. The hydronium ions of acid rain also mobilize toxins such as aluminium, and leach away essential nutrients and minerals such as magnesium.
2 H+ (aq) + Mg2+ (clay) f/b rx 2 H+ (clay) + Mg2+ (aq)
Soil chemistry can be dramatically changed when base cations, such as calcium and magnesium, are leached by acid rain thereby affecting sensitive species, such as sugar maple (Acer saccharum).
Forests and other vegetation
Adverse effects may be indirectly related to acid rain, like the acid's effects on soil (see above) or high concentration of gaseous precursors to acid rain. High altitude forests are especially vulnerable as they are often surrounded by clouds and fog which are more acidic than rain.
Other plants can also be damaged by acid rain, but the effect on food crops is minimized by the application of lime and fertilizers to replace lost nutrients. In cultivated areas, limestone may also be added to increase the ability of the soil to keep the pH stable, but this tactic is largely unusable in the case of wilderness lands. When calcium is leached from the needles of red spruce, these trees become less cold tolerant and exhibit winter injury and even death.
Human health
Scientists have suggested direct links to human health. Fine particles, a large fraction of which are formed from the same gases as acid rain (sulfur dioxide and nitrogen dioxide), have been shown to cause illness and premature deaths such as cancer and other diseases. For more information on the health effects of aerosols see particulate health effects.
Other adverse effects
Acid rain can also damage buildings and historic monuments, especially those made of rocks such as limestone and marble containing large amounts of calcium carbonate. Acids in the rain react with the calcium compounds in the stones to create gypsum, which then flakes off.
CaCO3 (s) + H2S04(aq) f/b rx CaSO4 (aq) + CO2 (g) + H20(l)

The effects of this are commonly seen on old gravestones, where acid rain can cause the inscriptions to become completely illegible. Acid rain also increases the oxidation rate of metals, in particular copper and bronze.
Affected areas
Places with significant impact by acid rain around the globe include most of eastern Europe from Poland northward into Scandinavia, the eastern third of the United States, and South Western Canada. Other affected areas include the South Eastern coast of China and Taiwan.
Potential problem areas in the future
Places like much of Southeast Asia (Indonesia, Malaysia and Thailand), Western South Africa (the country), Southern India and Sri Lanka and even West Africa (countries like Ghana, Togo and Nigeria) could all be prone to acidic rainfall in the future.
Posted by.... Ma'ruf Umar