(File photo)

PUNE: Pollution is causing ‘life-giving’ rain to become increasingly acidic in many parts of the country , particularly in the last decade, research by India Meteorological Department and Indian Institute of Tropical Meteorology has revealed.

Analysis of rainwater samples from Nagpur, Mohanbari (in Assam), Allahabad, Visakhapatnam and Kodaikanal in the decade 2001-2012 showed a pH level varying from 4.77 to 5.32, indicating that these places have actually been receiving ‘acid rain’.

Rainwater with pH below 5.65 is considered acidic. Potential of hydrogen, or pH, is a scale to measure acidity or alkalinity of a solution, where 7 is ‘neutral’. For lesser values, acidity increases with decreasing count. Acid rain is a result of rain water in the atmosphere mixing with polluting gases such as oxides of sulphur and nitrogen emitted from power plants, automobiles and some industrial units.

Acid rain can reduce soil nutrition, corrode buildings (such as Taj Mahal), kill aquatic life and increase heavy metal concentration in soil and water, impacting human health.

Acid rain causes leaching of soil nutrients, which means that these nutrients are not available to plants and crops grown in the soil, affecting productivity. Acid rain has had a corrosive effect on monuments,” experts said. Acid rain can also dissolve salts of heavy metals found in rocks and soil. These heavy metals then find their way into agriculture fields, water sources and ultimately human physiologies. According to the study by scientists V Vizaya Bhaskar and P S P Rao, which was published in the Journal of Atmospheric Chemistry, almost all global atmosphere watch (GAW) stations in India showed a decreasing trend in pH levels with each passing decade during the period of analysis (1981 to 2012).

