Acid Rain

Acid Rain

Rain tends to be naturally acidic with a PH of 5.6 to 5.7. This is due to the reaction of atmospheric CO2 with water to produce carbonic acid. Other atmospheric substances from volcanic eruptions, forest fires, and other natural phenomenon also contribute to the natural acidification of rain. This natural level of acidity is sufficient enough to dissolve minerals into the earth's crust and make them available to plant and animal life and not acidic enough to inflict any damage.
Formation:
The contribution of sulfur dioxide (SO2) and Nitrogen dioxide (NO2) from anthropogenic sources disturbs the acid balance of rain and converts the natural and mildly acidic rain into precipitation with far reaching environmental consequences. The reactions of SO2 and NOx in the atmosphere yield H2SO4 (sulfuric acid) and HNO3 (nitric acid) droplets. These acids are formed in a series of photochemical and chemical reactions and are catalysed by other substances present in the atmosphere. The acidic droplets are partly neutralized by bases (salts) such as particulate lime and ammonia (NH3). These salts and the remaining H2SO4 and HNO3 droplets along with hydrochloric acid (HCl) released into the atmosphere by man-made and natural activities give rise to acidic precipitation, popularly known as acid rain. Acid rain comprises of more H2SO4 than HNO3.
Occurrence:
Acid rainfall may occur at a place far away from pollution sources (up to 1000 km) Events of acid rain in Sweden and Canada have been traced to large SOx emissions from densely populated areas of the United Kingdom and United States, respectively.
Damage:
Acid rain is a manifest of major consequences of air pollution because of the large amounts of SOx and NOx. It may cause extensive damage to materials and ecosystems. Following are some of the damages caused by acid rain:

• Damage to buildings, structural material, and valuable ancient sculptures carved from marble, limestone, sandstone etc.
• Damage to crops and forests, leaching of nutrients from leaves, and alteration of seed germination characteristics. Damage to young growing plant tissues and the process of photosynthesis, hence hindering the development of plants and threatening their very survival.
• Acidification of soils with consequent effects on microbial and soil fauna and nitrogen fixation
• Alterations of soil chemistry leading to reduced forest productivity· Potential effects on aquatic systems such as acidification, decreased alkalinity, and mobilization of metals like aluminium
• Other biological effects on aquatic biota such as altered species composition among plankton, vegetation, and invertebrates; decline in productivity of fish and amphibians; skeletal deformity; and increased fish mortality
• Corrosive damage to steel, zinc, oil-based paints and automobile coatings
• Possible effects on human: lungs, skin, and hair may be affected; acidification of drinking water reservoirs and concurrent increases in heavy metals may exceed public health limits