ATMOSPHERIC POLLUTANTS AND THEIR INFLUENCE ON ACIDIFICATION OF RAIN WATER AT AN INDUSTRIAL-LOCATION ON THE WEST-COAST OF INDIA

The chemical analysis of rain water samples at 11 locations along with measurements of atmospheric aerosols and their size distributions were made to study the influence of pollutants on acidification of rain water during the monsoon season of 1990 at Chembur-Trombay area, a highly industrialized belt in Bombay region located on the west coast of India. The concentrations of acid precursor gases, namely, SO2 and NO2 emanating from industries were low and their influence on acidification was limited to a few kilometer radius of their sources. Whereas, the deposition of ionic components (Na+, K+, Ca2+, Mg2+ and Cl-) whose sources are natural (sea and soil) were uniformly distributed throughout the region as compared to those released from man-made sources. The high concentration of alkaline components, especially Ca2+ from natural sources and NH3 released from a fertilizer plant, were responsible for neutralising H+ ion concentration generated from the acidic components (SO4(2-) and NO3-). The variation from acidic (1970s) to alkaline (1990s) nature of rain water in the area may be due to the change in the use of fuel from coal to natural gas, which contains less sulphur and also, the pollution control measures taken by the industries.