Publications

Bhattarai, H; Tripathee, L; Kang, SC; Chen, PF; Sharma, CM; Ram, K; Guo, JM; Rupakheti, M (2022). Nitrogenous and carbonaceous aerosols in PM 2.5 and TSP during pre-monsoon: Characteristics and sources in the highly polluted mountain valley. JOURNAL OF ENVIRONMENTAL SCIENCES, 115, 10-24.

Abstract
This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM 2.5 and TSP during pre-monsoon (March-May 2018) from a highly polluted urban Kathmandu Valley (KV) of the Himalayan foothills. The mean mass concentration of PM 2.5 (129.8 mu g/m 3 ) was only tilde 25% of TSP mass (558.7 mu g/ m 3 ) indicating the dominance of coarser mode aerosols. However, the mean concentration as well as fractional contributions of water-soluble total nitrogen (WSTN) and carbonaceous species reveal their predominance in find-mode aerosols. The mean mass concentration of WSTN was 17.43 +4.70 mu g/m 3 (14%) in PM 2.5 and 24.64 +8.07 mu g/m 3 (5%) in TSP. Moreover, the fractional contribution of total carbonaceous aerosols (TCA) is much higher in PM 2.5 ( tilde 34%) than that in TSP ( tilde 20%). The relatively low OC/EC ratio in PM 2.5 (3.03 + 1.47) and TSP (4.64 + 1.73) suggests fossil fuel combustion as the major sources of carbonaceous aerosols with contributions from secondary organic aerosols. Five-day air mass back trajectories simulated with the HYSPLIT model, together with MODIS fire counts indicate the influence of local emissions as well as transported pollutants from the Indo-Gangetic Plain region to the south of the Himalayan foothills. Principal component analysis (PCA) also suggests a mixed contribution from other local anthropogenic, biomass burning, and crustal sources. Our results highlight that it is necessary to control local emissions as well as regional transport while designing mitigation measures to reduce the KV's air pollution. (c) 2021 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

DOI:
10.1016/j.jes.2021.06.0181001-0742

ISSN:
1878-7320