Assessment of entrainment of key PAHs emanating from major combustion sources into the ambient air

Abstract

Increasing health problems owing to air pollution is the major cause of concern in the present time, especially in regions with exceptionally high particulate matter (PM) namely Indo-Gangetic Plains (IGP). In the ambient PM, polycyclic aromatic hydrocarbons (PAHs) have been reported to be carcinogenic in nature and its dominant sources are diesel emissions, coal combustion, agricultural waste burning, wood, and cow-dung cake burning. The chemical characteristics of particulate-bound PAHs from all the mentioned sources, their intercomparison, and entrainment into the atmosphere have been assessed in this study. High-molecular weight (HMW) PAHs fraction is highest in emissions from coal combustion (∼95%), followed by agricultural waste burning (83%), wood burning (83%) and cow-dung cake (77%) combustion. Among all the PAH compounds, benzo (b,j) fluoranthene (B[bj]F) was found to be predominant (highest in wood combustion ∼20.3%) in all source samples except exhaust from diesel and bio-diesel engine installed with diesel oxidation catalyst (DOC). Dominant PAH compounds contributing to the carcinogenic potential (CP) are benzo (a) pyrene (B[a]P), dibenzo (a,h) anthracene (D[ah]A), benzo (b,j) fluoranthene (B[bj]F), benzo (a) anthracene (B[a]A) and indeno (1,2,3-c,d) pyrene (IP). Wood combustion (CP = 1.4 ± 0.8) emission is observed to be the most carcinogenic followed by coal combustion (0.8 ± 0.2), diesel exhaust emission (0.4 ± 0.3), cow-dung cake burning (0.2), and agricultural waste burning (0.2 ± 0.1). Further, the range of various diagnostic ratios for each of the source samples has been reported that can be utilized in future studies for more comprehensive source apportionment.