Profile of Atmospheric PAHs in Rawalpindi, Lahore and Gujranwala Districts of Punjab Province (Pakistan)

ABSTRACT

In this study, polyurethane foam passive air samplers (PUF-PAS) were deployed to evaluate the atmospheric concentration levels and ambient exposure of polycyclic aromatic hydrocarbons (PAHs) in Gujranwala, Lahore and Rawalpindi districts of the Punjab Province (Pakistan). The PAHs were extracted from the PUFs disks using Soxhlet extraction assembly, and were further concentrated using rotary evaporator, purified on a column, packed with alumina/silica, and eluted with a solution of dichloromethane:hexane (1:1 v:v). The PAHs quantification was carried out gas-chromatograph equipped with a mass-spectrometer (GC-MS). Regression scatter plots and molecular diagnostic ratios were used to identify and characterize the emission of PAH species from different sources. Among all detected PAHs, a high concentration of naphthalene (Naph) was observed in Lahore (327 pg m^–3) and Rawalpindi (316 pg m^–3) cities followed by phenanthrene, banzo(a)pyrene, pyrene, benzo(b)florenthene and benzo(k)flourenthene. Our findings revealed that the low molecular weight (LM)-PAHs in Rawalpindi and Gujranwala cities could have possibly originated from a local petroleum refinery and vehicular emissions respectively, whereas the high molecular weight (HM)-PAHs observed in Wazirabad, could be largely related to both biomass and traffic emissions. Results also showed that ~88 percent of the atmospheric PAHs could be attributed to the wood combustions (R² = 0.88), out of which more than 50 percent of wood combustion were possibly with the brick kiln sector (R² = 0.53).