Characteristics and Sources of PAHs, Hopanes, and Elements in PM 10 Aerosol in Tulsipur and Charikot (Nepal)

Concentration of PAHs, hopanes, and elements in PM 10 aerosol samples was measured in two Nepalese urban centers, Tulsipur (725 m above sea level; 150,000 inhabitants) and Charikot (1,550 m above sea level; 23,000 inhabitants) in the monsoon period (August 2018) and pre-monsoon period (April–May 2019). The 24-h PM 10 limit value of 50 µg m −3 for human health was significantly exceeded at all locations, and the Nepal concentration limit of 150 µg m −3 was exceeded at Tulsipur-bus station, Tulsipur-village, and Charikot-hospital in the pre-monsoon season. The average daily PM 10 and PAHs concentrations showed seasonal variations, with lower concentrations in the monsoon season and the higher values in pre-monsoon season. The average daily PM 10 and PAHs concentrations in the both sites were 133 μg m −3 and 23.8 ng m −3 in the pre-monsoon period and 49.6 μg m −3 and 2.30 ng m −3 in the monsoon period, respectively. The average daily hopane concentration during the pre-monsoon period was 1.40 ng m −3 in Tulsipur and 0.70 ng m −3 in Charikot. The IndP / (IndP + BghiP) ratio was higher than 0.5 during monsoon period, indicating combustion of biomass and charcoal burning. IndP / (IndP + BghiP) between 0.2 and 0.5 during pre-monsoon season indicates petroleum combustion. Fla / (Fla + Pyr) ratio between 0.3 and 0.5 during pre-monsoon and monsoon periods indicates high proportion of petroleum product combustion. The biomass burning associated with dense traffic in the center of the two cities was the main source of PAHs. The average daily element concentration was 6.80 ng m −3 in both locations during the monsoon period.