Japan Geoscience Union Meeting 2016

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Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG09] Interrelation between Life, Water, Mineral, and Atmosphere

Mon. May 23, 2016 3:30 PM - 5:00 PM A02 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Yohey Suzuki(Graduate School of Science, The University of Tokyo), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Naganuma(Graduate School of Biosphere Science), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Fumito Shiraishi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Chair:Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo)

3:45 PM - 4:00 PM

[BCG09-07] Adsorption behavior of organoarsenic compounds in soils
– Influence of organic matters –

*Masato Tanaka1, Yoshio Takahashi1 (1.Graduate School of Science, The University of Tokyo)

Keywords:organoarsenic compound, adsorption, soil, XAFS

Anthropogenic originated organoarsenic compounds such as diphenylarsinic acid (DPAA) are a water pollution source as well as naturally occurring inorganic ones. For example, DPAA polluted well water caused serious health problems in Kamisu, Japan. However, their adsorption behavior in soils is still well unknown. In general, the adsorption property of chemical compounds influences its migration process in natural environments such as soil-water system. In soils, organic matters (OMs) affect adsorption behavior of trace metals on minerals. Thus, it is important to understand the adsorption mechanism of the arsenic compounds with taking account of influence of OMs to predict future fate of them in environment. In this study, we conducted adsorption experiments for several soils which have different contents of Fe/Al-(oxyhydr)oxides and OMs, and adsorption amounts and structures were analyzed by ICP-MS and As K-edge XAFS measurements. The same experiments and analysis were conducted with OM extracted soils to understand the influence of OMs.
The As K-edge EXAFS spectra for arsenic compounds adsorbed on soil samples were well fitted with corresponding EXAFS spectra As adsorbed on Fe- and Al-(oxyhydr)oxides. The fact indicates that these arsenic compounds adsorbed on these minerals mainly. The adsorption ratios for Fe- and Al-(oxyhydr)oxides were estimated by the fitting, and the deviation of the ratio from the Fe/Al content was larger with increasing the OM content in soils. In addition, in most cases, the adsorption amounts of arsenic compounds increased by removing OMs. Thus, it is considered that the OMs prevent arsenic compounds from being adsorbed on minerals by covering their surface. However, even though OMs were removed from soils, the adsorption ratios were still not always reflected Fe/Al content ratio by removing OMs depending on the arsenic compounds. This fact indicates that the affinity of arsenic compounds for Fe/Al-(oxyhydr)oxides is different.