Size distribution and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in aerosol particle samples from the atmospheric environment of Delhi, India

Ambient aerosol particles were collected using a five-stage impactor at six different sites in Delhi. The impactor segregates the TSPM into five different sizes (viz. > 10.9, 10.9-5.4, 5.4-1.6, 1.6-0.7, and < 0.7 μm). Samples collected were chemically analyzed for all the five size ranges, for the estimation of 16 different PAHs. The particle size distribution of PAHs was observed to be unimodal in nature with the highest peak towards the smallest size aerosol particle (< 0.7 μm). The five size ranges were categorized into two broad categories viz. coarse (> 10.9 + 10.9 to 5.4 + 5.4 to 1.6 μm) and fine (1.6 to 0.7 + < 0.7 μm). It was observed that the dominant PAHs found were pyrene, benzo(a)pyrene, benzo(ghi)perylene and benzo(b)fluoranthene for both the coarse and fine fractions. Source apportionment of polycyclic aromatic hydrocarbons (PAHs) has been carried out using principal component analysis method (PCA) in both coarse and fine size modes. The major sources identified in this study, responsible for the elevated concentration of PAHs in Delhi, are vehicular emission and coal combustion. Some contribution from biomass burning was also observed.