Characterization of particulate-bound polycyclic aromatic hydrocarbons and trace metals composition of urban air in Delhi, India

The concentrations of sixteen polycyclic aromatic hydrocarbons (PAHs) and trace metals adsorbed to respirable particulate matter (PM ≤ 10 μm) and the fine fraction of particulate matter (PM ≤ 2.5 μm) were determined at a site in Delhi (India) during the winter and summer periods in 2007–2008. The annual mean concentrations for PM10 and PM2.5 were 138.5 ± 40.4 μg m−3 and 50.6 ± 20.4 μg m−3, respectively, with higher concentrations during winter than summer period. Concentrations of PM10 and PM2.5 have been found that were higher than the prescribed limits of the WHO and the NAAQS given by CPCB, India. The trace metals detected in the PM10 and PM2.5 were Al, Ca, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn and their concentrations were similar to those observed in heavily polluted urban areas from local traffic and other anthropogenic emissions. Total PAH concentrations for PM10 and PM2.5 were much higher in winter (81.5 and 96 ng m−3, respectively) compared to summer (33.1 and 45.8 ng m−3, respectively) with high molecular weight homologues (4–6 ring PAHs), which account for 80–95.8% of total PAHs. In general, the PM2.5 PAH concentrations were higher than PM10 particles. The results of diagnostic ratio and enrichment factor analyses showed that vehicular and anthropogenic emissions related to combustion, industrial processes as well as natural sources associated with the transport of dust from the roadside area were the main pollutant sources for PAHs and trace metals.