title: Characterizations of atmospheric particulate-bound mercury in the Kathmandu Valley of Nepal, South Asia.
abstract: The Kathmandu Valley, located in the Himalayan foothills in Nepal, is heavily polluted. In order to investigate ambient particulate-bound mercury (Hg) in the Kathmandu Valley, a total 64 total suspended particulates (TSP) samples were collected from a sub-urban site in the Kathmandu Valley, the capital region of Nepal during a sampling period of an entire year (April 2013-April 2014). They were analyzed for ambient particulate-bound Hg (PBM) using thermal desorption combined with cold vapor atomic spectroscopy. In our knowledge, it is the first study of ambient PMB in the Kathmandu Valley and the surrounding broader Himalayan foothill region. The average concentration of PBM over the entire sampling period of a year was found to be 850.5 (±962.8) pg m-3in the Kathmandu Valley. This is comparable to those values reported in the polluted cities of China and significantly higher than those observed in most of urban areas in Asia and other regions of world. The daily average Hg contents in TSP (PBM/TSP) ranges from 269.7 to 7613.0ngg-1with an average of 2586.0 (±2072.1) ng g-1, indicating the high enrichment of Hg in TSP. The average concentrations of PBM were higher in the winter and pre-monsoon season than in the monsoon and post-monsoon season. The temporal variations in the strength of anthropogenic emission sources combined with other influencing factors, such as ambient temperature and the removal of atmospheric aerosols by wet scavenging are attributable to the seasonal variations of PBM. The considerably high dry deposition flux of PBM estimated by using a theoretical model was 135μgm-2yr-1at the Kathmandu Valley. This calls for an immediate attention to addressing ambient particulate Hg in the Kathmandu Valley, including considering it as a key component of future air quality monitoring activities and mitigation measures.
authors.affiliation: Key Laboratory of Tibetan Environment Changs and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli, Finland; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Junming
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: shichang.kang@lzb.ac.cn.
authors.forename: Shichang
authors.initials: S
authors.lastname: Kang
authors.affiliation: Key Laboratory of Tibetan Environment Changs and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Huang
authors.affiliation: Key Laboratory of Tibetan Environment Changs and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Qianggong
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Institute for Advanced Sustainability Studies, Potsdam 14467, Germany.
authors.forename: Maheswar
authors.initials: M
authors.lastname: Rupakheti
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Sun
authors.affiliation: Key Laboratory of Tibetan Environment Changs and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli, Finland.
authors.forename: Lekhendra
authors.initials: L
authors.lastname: Tripathee
authors.affiliation: Key Laboratory of Tibetan Environment Changs and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Dipesh
authors.initials: D
authors.lastname: Rupakheti
authors.affiliation: International Centre for Integrated Mountain Development, Kathmandu, Nepal.
authors.forename: Arnico K
authors.initials: AK
authors.lastname: Panday
authors.affiliation: Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130 Mikkeli, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Sillanpää
authors.affiliation: State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; Graduate University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Rukumesh
authors.initials: R
authors.lastname: Paudyal
keywords: Atmospheric particulate-bound mercury; Dry deposition flux; Kathmandu Valley; South Asia; Temporal variation