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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-448
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 May 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Atmospheric organochlorine pesticides and polychlorinated biphenyls in urban areas of Nepal: spatial variation, sources, temporal trends and long range transport potential
Balram Pokhrel1,3,4, Ping Gong1,2, Xiaoping Wang1,2,3, Sanjay Nath Khanal4, Jiao Ren1,3, Chuanfei Wang1,2, Shaopeng Gao1, and Tandong Yao1,2 1Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
3University of Chinese Academy of Sciences, Beijing 100049, China School of Science
4Kathmandu University, Dhulikhel, Nepal
Abstract. The study of persistent organic pollutants (POPs) in low latitude tropical and subtropical urban cities is necessary to assess their local and global impacts on ecosystems and human health. Despite studies on levels of POPs in water, soils, and sediments, analysis of the distribution patterns, seasonality and sources of POPs in urban regions of Nepal remain limited. Polyurethane foam (PUF)-based passive air samplers were deployed in three major cities in Nepal: Kathmandu (the capital city), Pokhara and Hetauda (agricultural cities). Dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) were the dominant organochlorine pesticides in the atmosphere at all sites. The average concentrations of POPs were: ∑DDTs, 11.0–885.2 pg/m3; ∑HCHs, 4.0–2623.8 pg/m3; HCB, 2.7–186.2 pg/m3; ∑endosulfan, 1.4–34.8 pg/m3; and ∑6PCBs, 1.4–29.2 pg/m3. Isomer and metabolite ratio analyses suggested that the concentrations present were from both new and historical applications of the POPs. Vegetable production sites and their market places appeared to be the major DDT and HCH source areas. Higher atmospheric concentrations of DDT and HCH occurred during the pre-monsoon and monsoon seasons, and winter, respectively, closely associated with their local application for soil preparation and vegetable spraying. The estimated travel distances of the POPs (HCB, α-HCH, γ-HCH, and p,p'-DDT) under the Nepalese tropical climate were all above 1000 km, suggesting that high precipitation levels in the tropical climate were not enough to scavenge the POPs and that Nepal could be an important source region for POPs. Due to their close proximity and cold trapping (driven by low temperatures), the high Himalayas and the Tibetan Plateau are likely the key receptors of POPs emitted in Nepal. These results add to the information available on POPs from tropical developing countries.

Citation: Pokhrel, B., Gong, P., Wang, X., Khanal, S. N., Ren, J., Wang, C., Gao, S., and Yao, T.: Atmospheric organochlorine pesticides and polychlorinated biphenyls in urban areas of Nepal: spatial variation, sources, temporal trends and long range transport potential, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-448, in review, 2017.
Balram Pokhrel et al.
Balram Pokhrel et al.
Balram Pokhrel et al.

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Short summary
As a tropical country close to the Himalayas, it is essential to investigate concentration levels, and long range transport potential of persistent organic pollutants (POPs) in Nepalese cities to assess whether these pollutants can contaminate the high Himalaya. We found high concentration and long travel distance (> 1000 km) of dichlorodiphenyl- trichloroethane (DDT) and hexachlorocyclohexane (HCH) in atmosphere of Nepal cities, suggesting Nepal can be an important regional source region for POPs.
As a tropical country close to the Himalayas, it is essential to investigate concentration...
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