Wintertime characteristics of carbonaceous species of PM₁₀ over the Himalayan region of India

The present study analyses the carbonaceous species of PM₁₀ collected at Mohal-Kullu (31.9 °N, 77.11 °E; 1154 m asl), Nainital (29.39 °N, 79.45 °E; 1959 m asl) and Darjeeling (27.01 °N and 88.15 °E; 2200 m asl) during winter (January- February 2019). The concentration of PM₁₀ were recorded as 51 ± 16 μg m^-3, 38 ± 9 μg m^-3 and 52 ± 18 μg m^-3 for Mohal-Kullu, Nainital and Darjeeling, respectively. Organic carbon (OC) dominated over elemental carbon (EC) and was found to be 50.2%, 42.8% and 47% in total carbonaceous aerosols (TCA) at Mohal-Kullu, Nainital and Darjeeling, respectively. The concentrations of carbonaceous species were higher at Mohal-Kullu (OC: 11.1 ± 5.3, EC: 4.2 ± 1.9, WSOC: 5.3 ± 1.3 μg m^-3 and TCA: 22.1 ± 10.4 μg m^-3) followed by Darjeeling (OC: 5.4 ± 2.0, EC: 2.7 ± 1.0, WSOC: 3.9 ± 1.3 μg m^-3 and TCA: 22.1 ± 10.4 μg m^-3) and Nainital (OC: 2.9 ± 1.0, EC: 1.3 ± 0.6, WSOC: 2.1 ± 0.6 μg m^-3 and TCA: 6.7 ± 2.4 μg m^-3). The diagnostic ratios (OC/EC and WSOC/OC) are used to characterize the pollution sources and provides information on the ageing of aerosols and their emission sources The OC/EC and WSOC/OC ratio at Mohal- Kullu (2.6 ± 0.3, 0.6 ± 0.2), Nainital (2.0 ± 0.4, 0.7 ± 0.2) and Darjeeling (2.3 ± 0.5, 0.7 ± 0.2), respectively, indicates the dominance of fossil fuel combustion (coal and vehicular exhaust), with signified additional contribution from secondary organic carbon (SOC).