Calcium carbonates particles have also been frequently
observed in airborne PM sample (Ro et al. 2001; Li et al.
2003). In this study, presence of calcite (CaCO3) and
dolomite (Ca Mg (CO3)2) have also been identified by
XRD study (Fig. 3). These alkaline particles can absorb the
acidic gases such as SO2 and NO2 (Li and Shao 2009b) and
help to reduce the acidity of PM. Even though, percentage
contribution of this mineral is relatively very low. SEM
and EDS mapping results are shown in Fig. 7 where
qualitative identification of the elemental composition of
the particles of a selected area of the filter paper showed
the distribution of the Ca, C and O along with some Si
particles implies the presence of CaCO3. The SEM
micrograph in Fig. 7 showed that the particle on the filter
paper tend to form large conglomerates of smaller Ca
particles interspersed with the significant amounts of C and
O. The elemental EDS scan also showed the amount of Si
in very small particles. Presence of these minerals in Pune
City may be due to the site, which is covered with the
rocky hills.