Analysis of wet precipitation of air pollutants in Mumbai (India).

Bulk precipitation samples at Mumbai (India) were collected during the monsoon seasons of 1991 to 1996 and analysed for ionic concentrations using an Ion Chromatograph DIONEX model 100. The variability of sulphate to nitrate ratio in rainwater fluctuates in a wide range from 1.5 to 20 and governed by the sulphate concentrations in the sample. The regression analysis of the data reveals that in the bulk precipitation at Mumbai, SO4(2-) is becoming increasingly important relative to NO3-. The role of meteorological influences on scavenging of air pollutants by rain water has been tried to explain the phenomena. The computed wet deposition rates for S and N during 1991-1996 show that the S deposition is higher than N in all the years. There is a wide fluctuation in deposition rates of S ranging from 2 to 55 kg km2 per annum.