Observation and analysis of speciated atmospheric mercury in Shangri-La, Tibetan Plateau, China
- 1State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
- 2University of Chinese Academy of Sciences, Beijing 100049, China
- 3Department of Civil Engineering, Lamar University, Beaumont, Texas 77710, USA
- 4College of Energy and Environment, South China University of Technology, Guangzhou 510006, China
Abstract. This study reports the concentrations and potential sources of speciated atmospheric mercury at the Shangri-La Atmosphere Watch Regional Station (SAWRS), a pristine high-altitude site (3580 m a.s.l.) in Tibetan Plateau, China. Total gaseous mercury (TGM, defined as the sum of gaseous elemental mercury, GEM, and gaseous oxidized mercury, GOM), GOM and particulate-bound mercury (PBM) were monitored from November 2009 to November 2010 to investigate the characteristics and potential influence of the Indian summer monsoon (ISM) and the Westerlies on atmospheric transport of mercury. The mean concentrations (± standard deviation) of TGM, PBM and GOM were 2.55 ± 0.73 ng m−3, 38.82 ± 31.26 pg m−3 and 8.22 ± 7.90 pg m−3, respectively. A notable seasonal pattern of TGM concentrations was observed with higher concentrations at the beginning and the end of the ISM season. High TGM concentrations (> 2.5 ng m−3) were associated with the transport of dry air that carried regional anthropogenic emissions from both Chinese domestic and foreign (e.g., Myanmar, Bay of Bengal, and northern India) sources based on analysis of HYSPLIT4 back trajectories. Somewhat lower PBM and GOM levels during the ISM period were attributed to the enhanced wet scavenging. The high GOM and PBM were likely caused by local photo-chemical transformation under low RH and the domestic biofuel burning in cold seasons.