Acid Rain

Asia is currently the region most affected by acidification.
Acid rain primarily results from the transformation of sulphur dioxide (SO2) and nitrogen oxides into sulphuric acid (H2SO4), ammonium nitrate (NH4NO3) and nitric acid (HNO3). The transformation of SO2 and NO2 to acidic particles and vapours occurs as these pollutants are transported in the atmosphere over distances of hundreds to thousands of kilometres. Wet deposition is acid rain, the process by which acids with a pH normally below 5.6 are removed from the atmosphere in rain, snow, sleet or hail. The gases can then be converted into acids when they contact water.
A pH scale is used to measure the amount of acid in liquid-like water. Because acids release hydrogen ions, the acid content of a solution is based on the concentration of hydrogen ions and is expressed as "pH." This scale is used to measure the acidity of rain samples.
The smaller the number on the pH scale, the more acidic the substance is. Rain measuring between 0 and 5 on the pH scale is acidic and therefore called "acid rain." Small number changes on the pH scale actually mean large changes in acidity.

Causes of Acid rain
Sulphur dioxide (SO2) is generally a by-product of industrial processes and burning of fossil fuels. Ore smelting, coal-fired power generators and natural gas processing are the main contributors.
The main source of NOx emissions is the combustion of fuels in motor vehicles, residential and commercial furnaces, industrial and electrical-utility boilers and engines, and other equipment.
Effect of acidic rain on aquatic ecosystems
Most biological life survives best within a narrow range of pH levels, near neutral or 7.0. Aquatic vegetation and animal life vary in their susceptibility to changes in pH; some species are more acid-tolerant than others. Species higher up the food chain that relies on these organisms for food will be affected. If the pH levels drop below 5.0 most fish species are affected.
Effect of acidic rain on soils and plant growth
Some plants are tolerant of acidic conditions, while others are not. Acidic soils may affect microorganisms in the soil, which play important roles in plant growth. Acidity affects the availability of nutrients that are essential for plant growth . Nitrogen is a nutrient and at certain levels, nitrogen deposition from air emissions has increased growth of vegetation; however, at higher levels, excess nutrients can reduce plant growth. Plant leaves get burnt and dry.
Effect of acid rain on buildings and materials
Acidic rain is corrosive of metals and alkaline building materials such as marble and limestone. Urban areas subject to high levels of automobile exhaust and other sources of acidic rain have experienced significant weathering of statues and building materials. The important example of this is Taj Mahal, which looks darkened or yellow due to Acid rain caused by oil refinery near by.
Effect of acid rain on health
Acidic rain does not affect human health directly; however, the particulate matter associated with acid rain has been shown to have adverse health effects, particularly among those who have respiratory disorders. There is also some concern that acidic rain could contribute to leaching of toxins such as mercury that could be carried by runoff into bodies of water, contributing to environmental sources of this toxin.
The following are some more specific suggestions on what you, as an individual, can do:
In the home
* Run the washing machine with a full load.
* Hang dry some-or all-of the laundry.
* Buy energy-efficient appliances.
* Avoid the use of air conditioners altogether.
* Turn out the lights in empty rooms and when away from home.
* Consider installing compact fluorescent bulbs instead of high-wattage incandescent bulbs.
* If you have a forced-air furnace, change or clean its filters at least once a year.
* Avoid burning trash or leaves

While shopping
* Look for products bearing the EcoLogo. They minimize the use of environmentally hazardous substances and maximize energy efficiency and the use of recycled materials.
* Buy locally produced or grown items from local stores and businesses. They don't require the transportation energy of imported products.
* Transportation
* Walk, ride your bike or take a bus to work.
* Share a ride with a friend or co-worker.
* Have your engine tuned at least once every six months.
* Check your car tyre pressure regularly.
* Use alternative fuels, such as ethanol, propane or natural gas.
* Avoid unnecessary idling.
* Reduce the number of trips you make in your car.
* Drive at moderate speeds.
* Take the train or bus on long trips.
* Go CFC-Free. Control emission from vehicle. Check it regularly.
Conserve energy. Reduction in demand for oil and coal reduces the amount of acid rain.