Abstract
Abstract. To understand the ambient levels and sources of atmospheric mercury (Hg) in the Tibetan Plateau, a full-year continuous measurement of speciated atmospheric mercury was conducted at the Waliguan (WLG) Baseline Observatory (3816 m a.s.l.) from May 2012 to April 2013. Mean concentrations (± 1 SD) of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) during the whole study period were 1.90±0.80 ng m−3, 12.0±10.6 and 65.4±63.2 pg m−3, respectively. Seasonal variations of GEM were very small, while those of PBM were quite large with mean values being 4 times higher in the cold (102.3±66.7 pg m−3) than warm (22.8±14.6 pg m−3) season. Anthropogenic emissions to the east of the Tibetan Plateau contributed significantly to GEM pollution at WLG, while dust particles originating from desert and Gobi regions in Xinjiang province and the Tibetan Plateau to the west of WLG were responsible for PBM pollution at WLG. This finding is also supported by the significant positive correlation between daily PBM concentration and daily cumulative absorbing aerosol index (AAI) in air masses transported during the preceding 2 d.
Highlights
Mercury (Hg) is a toxic pollutant of global concern due to its long lifetime in air, bioaccumulation in aquatic systems, and detrimental impacts on human and animal health
The impact of regional and long-range transport of Hg originating from anthropogenic emissions on the elevated gaseous elemental mercury (GEM) level at WLG is discussed in detail in Sect. 3.2 and 3.3
This study presented the first full-year continuous speciated Hg dataset and identified potential sources causing high GEM and particulate bound mercury (PBM) at WLG in the Tibetan Plateau
Summary
Mercury (Hg) is a toxic pollutant of global concern due to its long lifetime in air, bioaccumulation in aquatic systems, and detrimental impacts on human and animal health. Atmospheric Hg is operationally defined in three forms, i.e., gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) These Hg species can be transformed among each other through complex physical and chemical processes (Selin, 2009; Lyman et al, 2020). GEM has a lifetime in air of 0.5–2 years, while GOM and PBM only have a lifetime of hours to weeks (Ariya et al, 2015; Murphy et al, 2006) Because of their different lifetimes, GEM can be transported globally via atmospheric circulation, whereas PBM is limited to regional transport (Pirrone et al, 2010). These Hg species can be removed from the atmosphere through dry and wet deposition processes. Once deposited to earth’s surface, Hg can be converted to methylmercury by biological processes, which can cause potential risks to ecological and human health
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