Urbanization and Air pollution are one of the biggest challenges the world is facing at present. The study mainly focuses on urbanization and air pollution of Bengaluru urban area, India, which is one of the fastest growing metropolitan cities in the world. The world is facing rapid urbanization and increase in the number of mega cities from 3 to 31 during 1975 – 2016. Air pollution is crossing the national ambient air quality standards in most of the urban areas. The same can be observed in Bengaluru at present. Decade 2001–2011 marked a population growth rate of 47.18% for Bengaluru urban agglomerate reaching a population of 9,621,551. It has a vehicular population of 7,028,067 and 13 Industrial areas in and around Bengaluru urban area at present. Ambient air quality parameters like SO2, NO2, Particulate Matter 2.5 (PM2.5), Particulate Matter 10 (PM10) and Air Quality Index (AQI) for 15 sampling stations of Bengaluru urban area covering industrial area, mixed urban area, sensitive areas were analyzed for the year 2011-2016. The PM10 concentration at 14 locations has crossed the national ambient air quality standard (60.0 µg/m3) by 30%-120%. The PM2.5 concentration at 9 locations has crossed the national ambient air quality standard (40.0 µg/m3) by 3%-45%. The concentration of SO2 is within the national ambient air quality standards (50.0 µg/m3). The concentration of NO2 at one station has crossed the national ambient air quality standards (50.0 µg/m3). The concentration of Pb varies between 0.1–0.3 µg/m3 at 13 locations. NH3, Pb and CO concentrations in ambient air are within the limits of national ambient air quality standards (100 µg/m3, 0.5 µg/m3 and 2 mg/m3). The ambient Air Quality Index of 15 sampling stations were in Satisfactory (51-100) and Moderate (101-200) range. During the nationwide strike, 22%-41% of reduction in the concentration of SO2 and 38%-77% of reduction in the concentration NO2 was observed. Industrial emissions, vehicular emissions and construction activities are identified as the major source of air pollution. The wet precipitation samples collected at Bengaluru during the 2013 monsoon season reported a pH of less than 5.6 and the presence of metals such as Fe, Mn, Zn, Al, Cr, Ni, Cd, Pb and Cu. Concentration of Fe was 0.27 mg/l in some of the wet precipitation samples and 0.01-0.41 mg/l in the harvested rainwater samples collected from the building roof catchment. This maximum concentration is higher than the acceptable drinking water standards. The source of metals was identified as particulate matter in atmosphere. It is an alarming situation.
Keywords : Urbanization, Air pollution, Harvested Rainwater, Metals.