Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-TT Technology & Techniques

[M-TT28] Frontiers in Geochemistry : Prospect for geochemistry and cosmochemistry in future

Sun. May 22, 2016 10:45 AM - 12:15 PM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Hajime Obata(Marine inorganic chemistry division, Atmosphere and Ocean Research Institute, University of Tokyo), Hirochika Sumino(Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo), Tetsuya Yokoyama(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Takafumi Hirata(Graduate School of Science, Kyoto University), Urumu Tsunogai(Graduate School of Environmental Studies, Nagoya University), Yoshio Takahashi(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Shogo Tachibana(Department of Natural History Scieces, Hokkaido University), Katsuhiko Suzuki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Gen Shimoda(Geological Survey of Japan, AIST), Hiroyuki Kagi(Geochemical Research Center, Graduate School of Science, University of Tokyo), Yusuke Yokoyama(Atmosphere and Ocean Research Institute, University of Tokyo), Chair:Hirochika Sumino(Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo), Tetsuya Yokoyama, Hajime Obata(Marine inorganic chemistry division, Atmosphere and Ocean Research Institute, University of Tokyo)

11:00 AM - 11:15 AM

[MTT28-08] Investigetion of atmospheric mercury isotopic compositions: technical development and applications

★Invited papers

*Akane Yamakawa1, Katsutoshi Moriya2, Jun Yoshinaga2, Yuanzhu Li2, Hitoshi CHIBA3, Katsuyuki Yamashita3, Atsushi Matsuki4 (1.National Institute for Environmental Studies, 2.The University of Tokyo, 3.Okayama University, 4.Kanazawa University)

Keywords:Mercury isotopes, MC-ICP-MS, atmospheric mercury

Mercury (Hg) is a toxic heavy metal, which exists in various chemical forms in the environmental system. In the atmosphere, Hg exists in three forms (Hg0(g), gaseous elemental Hg (GEM); Hg2+(g), gaseous oxidized Hg compounds; and Hg(p), particulate/aerosol bound Hg). Hg0(g) is the dominant species of atmospheric Hg, accounting for >95% of the total Hg in the atmosphere. Because Hg0(g) is highly volatile and has limited solubility in water, it cannot be easily removed by wet or dry deposition processes. Therefore, the residence time of Hg0(g) in the atmosphere is relatively long (0.5 to 1 years), which allows long-range transport from mercury emission source(s). Conversely, Hg+2(g) and Hg(p) are effectively removed from the atmosphere through wet and dry depositions. Because Hg0(g) deposit upon oxidation to Hg2+(g) far from its emission source(s), deposition on local/regional scales represents a combination of multiple sources of Hg (global, regional, or local; natural or anthropogenic).
Over the last decade, the development of analytical methods of highly precise Hg isotopic measurements demonstrated mass dependent fractionation (MDF) and mass independent fractionation (MIF) of Hg isotopes in environmental samples. MDF of Hg isotopes occur during various natural and industrial Hg transformations. MIF of Hg isotopes is observed during abiotic reduction, photochemical and non-photochemical, and physical and chemical processes. Such processes lead to differences in the Hg isotopic composition of different emission sources, both natural and anthropogenic, and atmospheric processes (i.e., transportation, oxidation/reduction, deposition, and reemission). Therefore, Hg isotopic compositions could be used as a tracer of the sources and processes of atmospheric Hg. In this study, we aimed to develop the methods of collection and pretreatment for isotopic measurement of Hg0(g), and then isotopic composition of Hg0(g) was investigated for various regions in Japan.
To identify potential mercury sources, air mass back trajectories were calculated for each sample using the NOAA HYSPLIT model. We divided the back trajectory patterns observed in the results into three groups of air masses predominantly derived from (1) a marine source derived from the Pacific Ocean, (2) coastal and land sources that probably contain anthropogenic mercury emitted from urban-industrial regions, and (3) continental sources associated with northwesterly flow at higher altitude (>1500 m) and long-range transportation. Although multiple sources were possibly impacted during the 24 hr ambient sampling, we were able to observe a correlation between the back-trajectory types and Hg isotopic composition.