Distribution of PM2.5 and PM10-2.5 in PM10 fraction in ambient air due to vehicular pollution in Kolkata megacity

This research paper aims at establishing baseline PM10 and PM2.5 concentration levels, which could be effectively used to develop and upgrade the standards in air pollution in developing countries. The relative contribution of fine fractions (PM2.5) and coarser fractions (PM10-2.5) to PM10 fractions were investigates in a megacity which is overcrowded and congested due to lack of road network and deteriorated air quality because of vehicular pollution. The present study was carried out during the winter of 2002. The average 24h PM10 concentration was 304 mu g/m(3), which is 3 times more than the Indian National Ambient Air Quality Standards (NAAQS) and higher PM10 concentration was due to fine fraction (PM2.5) released by vehicular exhaust. The 24h average PM2.5 concentration was found 179 mu g/m(3), which is exceeded USEPA and EU standards of 65 and 50 mu g/m(3) respectively for the winter. India does not have any PM2.5 standards. The 24 h average PM10-2.5 concentrations were found 126 mu g/m(3). The PM2.5 constituted more than 59% of PM10 and whereas PM10-PM2.5 fractions constituted 41% of PM10. The correlation between PM10 and PM2.5 was found higher as PM2.5 comprised major proportion of PM10 fractions contributed by vehicular emissions.