Source Attributes of PM2.5 Over the Indian Himalaya Using PMF and CWT Analysis
摘要
To develop management strategies to control human-induced air pollutants, it is important to examine the chemical species that influence PM2.5 concentrations and to quantify PM2.5 concentrations in urban environments. The present study examined the 24h average PM2.5 levels from July 2018 to December 2019 at three locations in the Indian Himalayan Region: Darjeeling, Almora, and Mohal-Kullu. During the measurement period, the average mass concentrations of PM2.5 were as follows: Mohal-Kullu, 39 ± 21 (range: 13–98 µg m−3); Almora, 27 ± 18 (range: 11–109 µg m−3); and Darjeeling, 38 ± 13 µg m−3 (range: 16–89 µg m−3). A significant positive correlation among NH4+, SO42−, NO3−, and Cl− in PM2.5 at the p < 0.05 significance level indicated formation of secondary inorganic aerosols (SIA) at the study sites. PMF 5.0 identified three to five major sources over the study sites: fossil fuel combustion, secondary aerosols, vehicular emissions, soil dust, and biomass burning. In Darjeeling, the five dominant sources were coal combustion (26%), vehicular emissions (24%), secondary aerosols (22%), soil dust (15%), and biomass burning (13%). PMF identified three mixed-type sources at Mohal-Kullu: soil dust plus vehicular emissions (35%), secondary aerosols (37%), and biomass burning (28%). At Almora, sources were soil dust (36%), biomass burning (28%), and secondary aerosols plus fossil fuel combustion (36%). The concentration-weighted trajectory (CWT) shows that significant emission sources were distributed across IHR. High concentrations and grid-cell values indicate strong local emission sources near the study sites. Additionally, transboundary transport of continental pollutants results in pollutant loading across the Himalayan region.