Journal of Geophysical Research: Atmospheres

Mercury in the marine boundary layer and seawater of the South China Sea: Concentrations, sea/air flux, and implication for land outflow

Authors

  • Xuewu Fu,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
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  • Xinbin Feng,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
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  • Gan Zhang,

    1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
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  • Weihai Xu,

    1. South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
    2. Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hong Kong
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  • Xiangdong Li,

    1. Department of Civil and Structural Engineering, Hong Kong Polytechnic University, Hong Kong
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  • Hen Yao,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
    2. Graduate University of the Chinese Academy of Sciences, Beijing, China
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  • Peng Liang,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
    2. Graduate University of the Chinese Academy of Sciences, Beijing, China
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  • Jun Li,

    1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
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  • Jonas Sommar,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
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  • Runsheng Yin,

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
    2. Graduate University of the Chinese Academy of Sciences, Beijing, China
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  • Na Liu

    1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
    2. Graduate University of the Chinese Academy of Sciences, Beijing, China
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Abstract

[1] Using R/V Shiyan 3 as a sampling platform, measurements of gaseous elemental mercury (GEM), surface seawater total mercury (THg), methyl mercury (MeHg), and dissolved gaseous mercury (DGM) were carried out above and in the South China Sea (SCS). Measurements were collected for 2 weeks (10 to 28 August 2007) during an oceanographic expedition, which circumnavigated the northern SCS from Guangzhou (Canton), Hainan Inland, the Philippines, and back to Guangzhou. GEM concentrations over the northern SCS ranged from 1.04 to 6.75 ng m−3 (mean: 2.62 ng m−3, median: 2.24 ng m−3). The spatial distribution of GEM was characterized by elevated concentrations near the coastal sites adjacent to mainland China and lower concentrations at stations in the open sea. Trajectory analysis revealed that high concentrations of GEM were generally related to air masses from south China and the Indochina peninsula, while lower concentrations of GEM were related to air masses from the open sea area, reflecting great Hg emissions from south China and Indochina peninsula. The mean concentrations of THg, MeHg, and DGM in surface seawater were 1.2 ± 0.3 ng L−1, 0.12 ± 0.05 ng L−1, and 36.5 ± 14.9 pg L−1, respectively. In general, THg and MeHg levels in the northern SCS were higher compared to results reported from most other oceans/seas. Elevated THg levels in the study area were likely attributed to significant Hg delivery from surrounding areas of the SCS primarily via atmospheric deposition and riverine input, whereas other sources like in situ production by various biotic and abiotic processes may be important for MeHg. Average sea/air flux of Hg in the study area was estimated using a gas exchange method (4.5 ± 3.4 ng m−2 h−1). This value was comparable to those from other coastal areas and generally higher than those from open sea environments, which may be attributed to the reemission of Hg previously transported to this area.

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