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 wer e made to study the influence of pollutants on acidification of rain w ater during the monsoon season of 1990 at Chembur-Trombay area, a high ly industrialized belt in Bombay region located on the west coast of I ndia. The concentrations of acid precursor gases, namely, SO2 and NO2 emanating from industries were low and their influence on acidificatio n was limited to a few kilometer radius of their sources. Whereas, the deposition of ionic components (Na+, K+, Ca2+, Mg2+ and Cl-) whose so urces are natural (sea and soil) were uniformly distributed throughout the region as compared to those released from man-made sources. The h igh concentration of alkaline components, especially Ca2+ from natural sources and NH3 released from a fertilizer plant, were responsible fo r neutralising H+ ion concentration generated from the acidic componen ts (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 th e use of fuel from coal to natural gas, which contains less sulphur an d also, the pollution control measures taken by the industries.