METAL UPTAKE IN BENTHIC ORGANISMS AND ARGILLACEOUS SEDIMENTS AFFECTED BY MINE DRAINAGE IN OGOYA, ISHIKAWA, JAPAN

概要

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A unique ecosystem composed of liverworts, diatoms, bacteria and argillaceous sediments is able to thrive in spite of acidic, sulfur and heavy metal contaminated water below the abandoned Ogoya Copper Mine in Ishikawa, Japan. Sample analyses by optical microscope, ED-XRF, XRD, SEM, TEM and FE-TEM revealed that Fe and Cu were taken up by benthic organisms and sediments. Metal uptake and precipitation, including adsorption by clay minerals, improves the water quality for surrounding organisms. Liverworts shelter diatoms and bacteria, also trapping sediments and precipitates that would otherwise be washed away. Meanwhile bacteria are involved in metal accumulation and converting toxic aqueous metals to minerals. Liverworts displayed Cu and occasionally Fe and Zn content. Clay sediments were enriched in Fe and sometimes S, with traces of Ti, Mn, Cu, Zn, and occasionally As, Br, Sr and Zr. Based on XRD analyses, chlorite, mica minerals, feldspar, quartz and chloritoid were predominant in the <2μm fraction of the river sediments, along with traces of the sulfate minerals melanterite, chalcanthite and despujolsite. Mine drainage has compromised the health of surrounding communities and damaged river ecosystems. Clarification and optimization of natural metal uptake processes and the fate of mine-related elements could hold keys to sustainable remediation methods for use in the Ogoya mine area.
日本粘土学会の論文