Wintertime Variation in Carbonaceous Components of PM10 in the High Altitudes of Himalayas

Abstract

Carbonaceous aerosols play a significant role in the Earth’s atmospheric system by affecting visibility, the hydrological cycle, the climate, radiative forcing, and human health. The present study analyses PM10 samples that were collected at three distinct urban locations (Mohal-Kullu, Nainital, and Darjeeling) over the Himalayan region of India during winter 2019. The mass concentrations 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% of total carbon (TC) at Mohal-Kullu, Nainital, and Darjeeling, respectively. The respective mass concentrations of carbonaceous species [OC, EC, water-soluble organic carbon (WSOC), and total carbonaceous aerosol (TCA)] 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 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).