微生物生成水酸化鉄の地球化学：無機水酸化鉄と異なる結晶構造や微量元素の吸着能

抄録

Adsorption chemistry of Fe(III) oxyhydroxides is one of the important topics because of their considerable impacts on trace element geochemistry in the surface environment. Although inorganic Fe(III) oxyhydroxides have been used as an absorbent for laboratory studies, there is a growing recognition that biogenic iron oxyhydroxides (BIOS) are dominant in the environment. The microbial organic materials in BIOS can dramatically change mineralogical and adsorptive characteristics of Fe(III) oxyhydroxides, but the details and their differences from inorganic Fe(III) oxyhydroxides have not been specified well. In this review, we introduce our recent findings of BIOS especially focusing on their crystal structure, mineral transformation during early diagenesis, and trace element adsorption. The microbe-mineral interactions in BIOS (i) change the mineral structure of ferrihydrite, (ii) limit the ratio of BIOS reduced under anoxic condition, and (iii) enhance adsorption of cesium cation whereas inhibit anion adsorption of selenate and selenite ions compared to inorganic Fe(III) oxyhydroxides. These results will provide new insight into the geochemical role of BIOS and also contribute to other scientific fields such as environmental engineering, environmental microbiology, and ore geology.