Size distribution of atmospheric aerosols in Kolkata, India and the assessment of pulmonary deposition of particle mass

Aerosol size distributions were measured at three stations in Kolkata city, during December 2003 to February 2004 using an 8-stage cascade impactor with a back-up filter. Hi-volume samplers were used at the 3 sites for measuring PM2.5 and PM10 concentration. The results showed that the total average number distributed in the size range of 0 to 10 mu m for particulates of size Dp could be represented as a Junge distribution dN/d log(Dp) = 1282.6 (Dp)(-3.803). Aerosol mass distribution by size showed that of the collected fractions most of the PM10 were in the size range of 0<0.43 mu m (15.73%) followed by 0.65<11.1 mu m (15.72%) and then 0.43 < Dp < 0.65 mu m (14.73%). Particle size distributions were trimodal with fine mode Dp<1.1% mu m (MMAD = 0.51 mu m, GSD = 2.15), medium mode 1.1<4.7 mu m (MMAD=2.53 mu m, GSD=1.54) and coarse mode 4.7<10 mu m (MMAD=8.16 mu m, GSD = 1.38). Average concentrations of PM2.5 and PM10 were in the range of 96.31-363.63 mu g.m(-3) and 140.50-637.70 mu g.m(-3), respectively. Correlation analysis showed that the highest correlation (0.91) was observed between the particle ranges of 9.0-10.0 mu m and 3.3-4.7 mu m followed by 0.89 between 9.0-10.0 and 5.8-9.0 mu m. Regression analysis showed that PM2.5 was about 60% of PM10 concentration. A widely used ICRP model was used to estimate pulmonary deposition. The result showed that 36% of deposited PM10 was accumulated in the alveolar region and nearly 49% of deposited PM10 was accumulated in the tracheobronchial region.