Measurements of Particulate (PM2.5), BC and Trace Gases Over the Northwestern Himalayan Region of India

Abstract

Ambient trace gases (NH3, NO, NO2 and SO2) and black carbon (BC) were measured along with particulate matter (PM2.5) over the northwestern Himalayan region (Palampur, Kullu, Shimla, Solan and Nahan) of Himachal Pradesh (HP), India in a campaign mode during 12–22 March 2013 to evaluate the ambient air quality of the region. The average mixing ratio of ambient NH3, NO, NO2 and SO2 were recorded as 7.1 ± 2.6, 3.1 ± 1.3, 3.9 ± 1.4 and 1.7 ± 0.7 ppb respectively over the northwestern Himalayan region. The average concentration of BC was estimated as 2.2 ± 0.5 µg m−3 over the region whereas average concentration of PM2.5 mass was estimated as 41.8 ± 7.9 µg m−3. The spatial variation of ambient trace gases (NH3, NO, NO2 and SO2), BC and PM2.5 over the northwestern Himalayan region, India reveals that the region is mainly influenced by local activities, i.e., tourism activities, agricultural activities, biomass burning and vehicular emission. A significant positive linear correlation of NH3 and NH4 + with SO4 2−, NO3 − and Cl− (NH4 + vs. SO4 2− , r 2 = 0.652; NH4 + vs. NO3 −, r 2 = 0.701; and NH4 + vs. Cl−, r 2 = 0.627) of the PM2.5 indicates the possible formation of (NH4)2SO4, NH4NO3 and NH4Cl aerosols over the region.