Earth System Science Programme and Graduate Division of Earth and Atmospheric Sciences, The Chinese University of Hong Kong, Hong Kong, China; Himalayan Environment Research Institute (HERI), Kathmandu 44602, Nepal.
State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou 730000, China; Himalayan Environment Research Institute (HERI), Kathmandu 44602, Nepal.
J Environ Sci (China). 2022 May;115:10-24. doi: 10.1016/j.jes.2021.06.018. Epub 2021 Aug 1.
This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM 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 (129.8 µg/m) was only 25% of TSP mass (558.7 µg/ m) 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 µg/m (14%) in PM and 24.64±8.07 µg/m (5%) in TSP. Moreover, the fractional contribution of total carbonaceous aerosols (TCA) is much higher in PM (34%) than that in TSP (~20%). The relatively low OC/EC ratio in PM (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.
本研究首次全面分析了喜马拉雅山麓高度污染的加德满都谷地（KV）前季风期（2018 年 3 月至 5 月）同时采集的 PM 和 TSP 中含氮和含碳气溶胶。PM 的平均质量浓度（129.8μg/m）仅约为 TSP 质量浓度（558.7μg/m）的 25%，表明粗颗粒模式气溶胶占主导地位。然而，水溶性总氮（WSTN）和含碳物质的平均浓度及其分数贡献表明，它们在细颗粒模式气溶胶中占主导地位。PM 中 WSTN 的平均质量浓度为 17.43±4.70μg/m（14%），TSP 中为 24.64±8.07μg/m（5%）。此外，总碳质气溶胶（TCA）在 PM 中的分数贡献（34%）远高于 TSP（20%）。PM（3.03±1.47）和 TSP（4.64±1.73）中 OC/EC 比值相对较低，表明碳质气溶胶主要来源于化石燃料燃烧，其次是二次有机气溶胶。HYSPLIT 模型模拟的五天空气团后向轨迹，以及 MODIS 火灾计数表明，当地排放以及从印度-恒河平原地区向南输送的污染物都对该地区产生了影响。主成分分析（PCA）也表明，其他当地人为、生物质燃烧和地壳来源也有混合贡献。研究结果强调，在设计减轻措施以减少 KV 的空气污染时，有必要控制当地排放以及区域传输。
