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Sources and environmental processes of polycyclic aromatic hydrocarbons and mercury along a southern slope of the Central Himalayas, Nepal


Semi-volatile pollutants can undergo long-range atmospheric transport from low-altitude source regions to high-altitude regions and then accumulate in surface matrices (soil and plants). The Himalayas is the highest mountain range worldwide, but there have been limited studies on the source, transport, and deposition of polycyclic aromatic hydrocarbons (PAHs) and mercury (Hg) in the region. In this study, atmospheric PAHs, and the PAHs and Hg in soil and foliage were determined along a transect on a southern slope of the Himalayas, Nepal. The study showed anthropogenic emissions of PAHs and Hg occurred in the lowland areas of Nepal, and upslope transport to the high-altitude regions happened for both pollutants. During the upslope transport, forest filter effect and snow scavenging may be the important factors that enhance the deposition of PAHs, contributing to the negative pattern between concentrations of PAHs and altitudes. On the contrary, more Hg accumulated in the high Himalayas, relating to the enhanced deposition in the high altitude caused by the higher input from upper atmosphere.

Distribution and environmental processes of PAHs and Hg along the southern slope of Himalayan mountain

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This work was supported by the National Natural Science Foundation of China (41571463, 41222010, and 41201489) and the Third Pole Environment (TPE) Program. We would like to thank the Kathmandu Center for Research and Education, Chinese Academy of Sciences and Tribhuvan University (KCRE, CAS & TU) for their help with the fieldwork. We also thank Lei Wang, who was at China University of Mining and Technology, Beijing, for analyzing the Hg concentrations in the samples. In addition, B.P. would like to thank Dr. Krishna Prasad Pokhrel for his assistance in preparing the map and other suggestions.

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Correspondence to Xiaoping Wang.

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Responsible editor: Hongwen Sun

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Pokhrel, B., Gong, P., Wang, X. et al. Sources and environmental processes of polycyclic aromatic hydrocarbons and mercury along a southern slope of the Central Himalayas, Nepal. Environ Sci Pollut Res 23, 13843–13852 (2016).

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  • Emission sources
  • Upslope transport
  • Deposition
  • Persistent toxic substances
  • Forest filter effect
  • Snow scavenging
  • Himalayas