Concentration, seasonality, and sources of trace elements in atmospheric aerosols from Godavari in the southern Himalayas

Bakhat Rawat, Chhatra Mani Sharma, Lekhendra Tripathee, Xin Wan, Zhiyuan Cong, Rukumesh Paudyal, Aastha Pandey, Kshitiz Kandel, Shichang Kang, Qianggong Zhang

Abstract

Atmospheric pollution has detrimental effects on human health and ecosystems. The southern region of the Himalayas, undergoing rapid urbanization and intense human activities, faces poor air quality marked by high aerosol loadings. In this study, we conducted a two-year PM₁₀ sampling in the suburban area (Godavari) of Kathmandu, a representative metropolis situated in the southern part of the central Himalayas. The trace elements were measured to depict aerosol-bound element loadings, seasonality, and potential sources. The mean concentrations of trace elements varied considerably, ranging from 0.27 ± 0.19 ng m⁻³ for Tl to 1252.78 ng m⁻³ for Zn. The average concentration of Co and Ni was 1.2 and 22.4 times higher, respectively, than those in Lhasa city in Tibet in the northern Himalayas. The concentration of Pb was 38 times lower than that in Lahore, Pakistan, and 9 times lower than urban sites in India. For the seasonality, the trace element concentrations displayed remarkable variation, with higher concentrations during the non-monsoon seasons and lower concentrations during the monsoon season. This trend was primarily influenced by anthropogenic activities such as low-grade fuel combustion in vehicles, coal combustion in brick kilns, and biomass burning, along with seasonal rainfall that induced aerosol washout. The enrichment factors (EFs) analysis revealed that Cd, Zn, Sb, Ni, Cu, Cr, and Pb had higher EFs, indicating their significant contributions from anthropogenic sources. In contrast, elements like Tl, Co, V, Cs, U, Ba, Th, and Sr, characterized by lower EFs, were mainly associated with natural sources. The Pb isotopic ratio profiles exhibited the Pb in PM₁₀ are derived major contribution from legacy lead. Biomass burning contributed to the Pb source in winter. These findings provide policymakers with valuable insights to develop guidelines and strategies aimed at improving air quality and mitigating the impact of aerosol pollution on human health in the Himalayan region.

Authors and Affiliations

Bakhat Rawat^abc, Chhatra Mani Sharma^d, Lekhendra Tripathee^e, Xin Wan^a, Zhiyuan Cong^af, Rukumesh Paudyal^e, Aastha Pandey^ab, Kshitiz Kandel^ab, Shichang Kang^be, Qianggong Zhang^ab

^aState Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China
^bUniversity of Chinese Academy of Sciences, Beijing, 100049, China
^cCentre for Atmospheric Chemistry, University of Wollongong (UOW), NSW, 2522, Australia
^dCentral Department of Environmental Science, Tribhuvan University, Kritipur, Kathmandu, Nepal
^eState Key Laboratory of Cryospheric Science, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou, 730000, China
^fSchool of Ecology and Environment, Tibet University, Lhasa, 850000, China

DOI: https://doi.org/10.1016/j.envpol.2024.123359