Study of precipitation chemistry over an industrial city

The growing trend of industrialization has marked impact on the atmospheric chemistry around the globe. Such impacts are also predicted for developing countries like India. Acid precipitation due to secondary pollutants is one of them. The present investigation was conducted with an aim of studying the precipitation chemistry over Asansol city, India during the monsoon season. The rain water samples, collected on event basis during the period of June to September 2006, were analyzed for HCO3-, Cl-, SO42-, NO3-, NH4+, K+, Na+, Mg2+, Ca2+ and pH using standard procedures. The study revealed that the precipitation was alkaline in nature with mean pH value of 6.08. Dominant anion in rain water samples was HCO3- (36%), whereas Ca2+ was highest among the cations (53%). The observed acidic events, based on pH value, were only 17%, indicating the alkaline components effectively neutralize rain water over the area. This was also supported by the total alkaline to acid ion ration of 1.05. The ratio of (NO3-+Cl-) and SO42- was >1, indicating that acidic properties were influenced by HNO3 and HCl. In the ratio between (Ca2++NH4+) and (NO3-+SO42-), values >1 were obtained, indicating significant alkaline influence, which effectively prevented acid depositions in the area.