Investigation of physical and optical properties of aerosol over high altitude stations along the sub-Himalayan region of North-Eastern India

• Published in: Atmospheric pollution research 2020-02, Vol.11 (2), p.383-392
• Main Authors: Borgohain, Arup, Kundu, S.S., Barman, Nilamoni, Raju, P.L.N., Roy, Rakesh, Saha, Biswajit, Ajay, P., Pathak, Binita, Bhuyan, P.K.
• Format: Article
• Language: English
• Subjects: Absorption Ångström exponent; Biomass burning; Compensation parameter; Ångström exponent
• ISSN: 1309-1042; 1309-1042
• DOI: 10.1016/j.apr.2019.11.010

The present study focuses on exploring the spectral dependency of atmospheric extinction, the size distribution of aerosols, black carbon concentration and absorption and compensation parameter along the sub-Himalayan region of northeastern India, a field campaign was conducted from 1st February to 20th February 2018. Measurements were taken at three different stations in Arunachal Pradesh i.e., Tawang (2990 m a.s.l), New Palin (1300 m a.s.l.), and Geku (200 m a.s.l.). Techniques of Ångström exponent's curvature effect has been used to determine the aerosol size distribution over the stations. The mean black carbon concentration was 3.98 ± 1.03 μg m−3, 4.27 ± 1.22 μg m−3 and 2.38 ± 1.05 μg m−3 at Tawang, New Palin, and Geku respectively. The daily mean absorption coefficient at 370 nm (σ370) was (1.46 ± 0.56) × 10−4, (1.84 ± 0.42) × 10−4, and (1.85 ± 1.8) × 10−4 at Tawang, New Palin, and Geku. Whereas daily mean absorption coefficient at 880 nm (σ880) was (0.33 ± 0.08) × 10−4, (0.42 ± 0.05) × 10−4, and (0.2 ± 0.17) × 10−4. The σ370 was 126%, 125%, and 164% higher than the absorption at the longer wavelength (880 nm) which indicates a higher biomass burning BC. The average Absorption Ångström Exponent (AAE) at 370–880 nm were 1.59 ± 0.23, 1.63 ± 0.23 and 2.28 ± 0.57 at Tawang, New Palin, and Geku. In addition, at Tawang, New Palin, and Geku, the average AAE in the shorter spectral range (370–520 nm) were 2.43 ± 0.97, 2.41 ± 1.22 and 3.09 ± 1.54, whereas in longer spectral range (520–880 nm) were 1.05 ± 0.05, 1.13 ± 0.18 and 1.44 ± 0.33, respectively. •Investigation of aerosol physical and optical properties along the sub-Himalayan region of northeastern India.•Biomass burning has a significant impact on the aerosol activities over the stations.•The variation in biomass causes the variation in Absorption Ångström Exponent values.