Mechanism Of Microorganisms On Migration And Transformation For Heavy Metal Cr In The Sediment-water Of The Wei River

Based on outdoor investigation and indoor-simulational experiment,in single and continuous extraction method,this paper reasearched the way how to release the potential and the geometrical shape of the Cr in the sediments distributed in Weihe river and weinan,and then analyzed the way how sediments affect the reduction and the adsorption of Cr.From the studies on experiments in anaerobic condition and aerobic condition,it analyzed the changes of Cr migration and the geometrical shape,that exists in sediment-water interface.And the same time,we used the means of microbial cultivation,purification,microscope observation and strain identification research,revealed the microbial influential mechanism about Cr migration and the geometrical shape.Then we can obtain valuable results shown as below:1)The basic characteristics of the sediments are:the pH of the sediments with different clay contents is neutral,with strong oxidizability,the conductivities is mostly above 600?m/cm,and the Cr in the sediments are higher than their environmental background values.The content of clay and organic matter in the Weinan sediments is higher than Xianyang sediments.At the same time,the water quality of the two sections of the Weihe River is good,and there is no excessive phenomenon at present.2)Sediments of the Weinan and Xianyang sections with different clay contents,the proportion of the Cr bioavailable state?exchangeable,carbonate bound,iron-manganese oxide bound,and organic bound state?of the sediment during continuous extraction Both are much smaller than the stable state of the residue,and the percentage of its residual state is mostly above>97%.The chromium adsorption and reduction experiments showed that the reduction rate of chromium was mostly above 40%,and the adsorption rate was lower,which was lower than 15%.The sediments with different clay contents have different effects on the extraction of chromium by a single extractant.The higher clay content in the Weinan part of the sediment is higher than the extraction rate of heavy metals Cr in the sediments CaCl2>DTPA>HCl,and the Xianyang section clay The lower content sediments were HCl>CaCl2>DTPA.Besides,the lower clay content in the Xianyang section was more likely to be released into the water environment than the sediments with lower clay content in Weinan section.3)Under the condition of high chromium water renewing,microorganisms adapt to the new environment and their numbers and population changes mainly through four periods:initial adaptation period,fewer microbial species and more miscellaneous species;during rapid growth period,the number of microorganisms continues to increase by more More;competitive growth period,the number of microorganisms gradually decreased,less bacteria;stable period,the number of microorganisms are stable high-Cr bacteria species?Bacillus cereus,Fusarium,Bacillus subtilis,and Bacillus falciparum?.And there is a higher concentration of microbial colonies and population in the higher levels of surface sediments in Weinan than sandy sediments in Xianyang.4)The contents of Cr⁶⁺at the sediment-water interface of the different clay contents in the Weinan segment and the Xianyang segment under the aerobic and anaerobic conditions both increased rapidly with the renewal rate of the water and then stabilized,and the content of Cr³⁺changed rapidly with the renewal rate of the water.After the growth,it continued to grow,but its growth rate was slower than before;under anaerobic conditions,the total Cr⁶⁺and Cr³⁺contents were higher than those under aerobic conditions.The contents of Cr⁶⁺and Cr³⁺in the Weinan segment were lower than those in Xianyang.This is mainly due to the high microbiological effects of clay and organic matter content in the sediments of the Minnan Section.The content of clay and organic matter in the sediments of the Xianyang Section is relatively low,and the valence of chromium is susceptible to changes in anaerobic environmental conditions.The release of chromium from the clay sediments in the southern segment of the province is smaller than that from the Xianyang section.5)Under the hydrodynamic effect,in the simulation experiment of sinks with different clay content sediments,the chromium in the surface layer of the sediment mainly exists in the residue state and the proportion is more than 95%.When the water body renewal rate increases gradually,the heavy metal chromium organism is effective.The proportion of states increases gradually,especially the proportion of Fe-Mn oxide bound and organic bound states.Under the aerobic and anaerobic conditions,the proportion of heavy metal Cr migration and transformation in the sediments of the Weinan Section and the Xianyang Section is as follows:the oxygen-Weinan Section,the anaerobic-Xianyang Section,the oxygen-Xianyang Section,and the anaerobic-Weinan Section.Compared with the chromium deposit form of the original sediment,in the simulation experiment of the sink,the chromium speciation increases from the stable residue state to the Fe-Mn oxide bound state and the organic bound state,and the release ratio is more easily released into the water environment.6)The reason why the chromium migration and conversion mechanism is due to the combined effects of microbes and physicochemical effects in the sediment-water interface of clayey soil sediments on the Weinan.Its microbial effect is manifested as Bacillus cereus and Bacillus subtilis release reducing enzymes,and that converts Cr⁶⁺to Cr³⁺to form Cr?OH?3.At the same time,the physical and chemical functions are mainly reducing ions to reduce Cr⁶⁺to Cr³⁺.Finally,part of the trivalent chromium precipitates naturally settles to the surface of the sediment,and part of the trivalent chromium precipitates and complexes with microorganisms to form micelles.The micelles are suspended in the water,thereby reducing the Chromium content in water.However,the migration and transformation of chromium at the sediment-water interface with small clay content in the Xianyang section is mainly affected by physical chemistry.The reducing ions convert hexavalent chromium into trivalent chromium and form a flocculent precipitate that is colloidally aggregated by organic matter to form colloidal aggregates,then it will be suspended in water.