Academic investigation of hot spring's microbial mats included high concentration of heavy metals (Au,Ag,Hg,Sr).

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In 2002 and 2003,field researches were carried out to investigate biomats in geothermal area and in hot springs in Kamchatka, Russia. We have observed bacteria in all cases which precipitate a significant amount of various heavy metals. In 2004,filed studies were achieved focusing biomats in Hokuto Hot Springs, Taiwan, and Tamagawa Hot Springs, Japan. The both hot springs are famous of precipitation of hokutolite, radioactive barite. In this study we observed γ-ray radioactivity of ^<226>Ra (42.2 Bq/g) and ^<228>Ra (1.35 Bq/g), and this indicate that ^<226>Ra of uranium series is predominant. In 2005,a collaborative research with the group of Prof.Muhongo, Dar Es Salaam University, Tanzania, was carried out targeting a mercury-pollution caused by the small-scale gold mining around Geita, on the south coast of Lake Victoria, Tanzania. Samples of water, sediments, soil, biomats and aerial dusts were collected around ten small-scale mining sites, and many observations were made such as mineral identification, analyses of chemical compositions, etc. Optical microscopy and electron microscopy elucidated mercury distribution concentrated around the cell of microorganisms and clay mineral particles. All these field researches and laboratory works on biomats found in geothermal area, hot springs and metal mines elucidated atmosphere-water-soil-microorganisms interactions and biomineralization. An important role of microorganisms and mechanisms in formation of heavy metal minerals were clarified in nanometer-scale using electron microscopes. These results are fundamental data valuable for application of bioremediation in heavy metal-polluted area.