Type | Working Paper |
Title | Interaction of Radioactive Substances, Salts and Microorganisms in Paddy Soils in Dodoma, Tanzania |
Author(s) | |
Publication (Day/Month/Year) | 2017 |
URL | http://dspace.lib.kanazawa-u.ac.jp/dspace/bitstream/2297/48037/1/Abstract-N-1123142404-kato-tomohiro.pdf |
Abstract | Microorganism tolerance to high radioactivity and salinity was discovered in the soils deposited from the weathered granite in Bahi Swamp of Dodoma Region, Tanzania, which has an area of 125 – 140 km2 and located approximately 50 km to the west of Dodoma. This swamp is underlain by layers of black clayey soils about 110 m thick. Some of the clay layers have been found to be radioactive due to their content of uranium-bearing minerals such as uranyl vanadates; (Ba, Pb)(UO2)2V2O8・5(H2O). The β(γ)-ray counts and trace elements were analyzed respectively by a scintillation counter and X-ray fluorescence (XRF) spectrometer. Salt and black clayey soils showed theirγ-ray radioactivity ranging from 130 to 200 cpm and contained Sr abundant, and Ga, Rb, Y, and Zr slightly less abundant, whereas La, Ce, Th and Ni detected slightly. Besides, their mineralogical characteristics were analyzed by using X-ray powder diffractometer (XRD), which identified clay minerals such as smectite, mica clay minerals and kaolin minerals whereas halite and bischofite in salts. The presence of microorganisms was observed with Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Analyzer (EDS), and Transmission Electron Microscopy (TEM). Filamentous bacteria were fully covered with flakes of clay minerals, which are recognized as kaolinite from its hexagonal particles. The clay minerals such as kaolinite, smectite, etc. could have functions to alleviate or even absorb the effect of the salinity and the radiation. This is the first report revealing high radioactivity of paddy soils and salt associated with microorganisms in Dodoma, Tanzania. |
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