Wintertime trends of particulate-bound polycyclic aromatic hydrocarbons (PAHs) at north-east site of India: chemical characterization and source identification

Particulate-bound Polycyclic Aromatic Hydrocarbons (PAHs) have been identified as pollutants of serious concern due to their severe health impacts on human and animal life. In the present work, 16 USEPA (United States Environmental Protection Agency) identified PAHs present in PM_2.5 at Jorhat, India during the winter months (Jan-March, 2020) were analyzed. Apart from the temporal variability of these compounds, the impact of varying meteorological factors like temperature, wind speed, relative humidity, and planetary boundary layer height on PAHs concentration have also been studied. It has been observed that the effect of ambient air temperature and planetary boundary layer on PAHs concentration are significant compared to other meteorological parameters during the winter season. The average concentration of total PAHs during this period was 157.2 ± 127.7 ng/m³ with dominance of high molecular weight aromatics compared to the low molecular weight ones. Among all 16 PAHs studied, the contribution of benzo(b,j)fluoranthene (27.26%) to total PAHs concentration was found to be the highest followed by di-benzo(a,h)anthracene (10.37%). Source identification analysis using isomeric PAHs ratios indicated that crop residue burning, vehicular emission, coal, and wood combustion are the major emission sources of PAHs. A comparative study of PAHs emission at the present site with other northern cities of India has been performed and it is observed that vehicular emission contributing to PAHs is common to all cities but in Kolkata, wood and coal combustion were also responsible for PAHs emission. Biomass burning is also seen to be a contributor to Amritsar. Whereas in Jorhat, crop residue and coal/wood combustion are seen to be major contributors to PM_2.5 bound PAHs unlike other cities.

Graphical abstract