The Environmental Chemical Effect Of Dissimilitary Iron Reduction On Cr(â…¥) Reduction In Paddy Soils

With the chromate used of industry in a wide range, the contaminants in river, soil and ground water have been become more and more serious. Cr(VI) could be directly reduce to Cr(III) by some microbes. This course can decrease the toxicity and migrate of Cr(VI). But this reduced ability may be weaken, because the toxicity of chromate and other factors in practice. Finding a way of repair the chromium(VI) in environment has became a pressing issue. Dissimilatory iron reduction is a microbial anaerobic respiration, Which with Fe(III) as the terminal electron acceptor and oxidize organic matter to gain energy. Dissimilatory iron reduction showed important environmental significances. It could promote some heavy metals change to the low valence by redox. Dissimilatory iron reducers could promote decomposition of some organic contaminants, so get the purpose of repair the polluted environment. At present , there seldom have the study connect Dissimilatory iron reduction and Cr(VI) reduction. Fe(III) and Cr(VI) may be generated a competition relation to electron when they consist in one system, and these two reduction process also been affected. So there has certain environmental significance to recover Cr(VI) contaminants in anaerobic conditions that study the relation between Fe(III) and Cr(VI) reduction.Through Co-culture experiment and slurry experiments in this paper, the interrelation of Fe(III) and Cr(VI) reduction was investigated; the difference in the carbon utilized of microbes from different paddy soils through the test of different carbon sources utilized; investigated the effect of electron shuttle (AQDS) on Cr(VI) and Fe(III) reduction; primary explore effect of iron reduction on soil remediation. Some results were obtained following:(1) Microbes could directly reduce Cr(VI) to Cr(III) through Cr(VI) as the sole electron acceptor. The reducing ability of microbes from different paddy soils is different. The reducing rate and quantity of microbes from Sichuan paddy soil was greater. The Cr(VI) reducing rate was decreased with the increase of Cr(VI) concentration. When the concentration of Cr(VI) up to 0.2 mmol/L, it could not be completely reduced in Co-culture experiment. And the organic matters and Fe(III) oxides in slurry experiments enhanced the reducing ability, Cr(VI) of 250mg/kg could be completely reduced. The reduced effect was better than in Co-culture experiment.