The Migration And Transformation Of Arsenic In Soil By Iron And Manganese Compounds

In recent years,the problem of arsenic（As）pollution in the soil of rice fields in south China has attracted more and more attention.As has strong toxicity and migration in the soil,which is easy to be absorbed by crops and enter the human body through the food chain,thus causing serious damage to the human body.At present,it is considered to be an economical and effective treatment plan to control soil As pollution and reduce crop As content by adding motivation agent.However,most studies focus on the migration and occurrence morphology of As in soil by observation agents,while few studies on the distribution characteristics and morphological transformation of As in soil solution after the application of motivation agents.Among the motivation agents,iron and manganese oxides are the most active minerals in the soil,which can significantly control the migration and transformation of oxygen-containing anions in the soil.Therefore,this study to some As typical of arsenic pollution in paddy soil in hunan province As the research object,to the soil exogenous add iron,manganese oxide（iron manganese acid,ferric sulfate,ferrous sulfate,polymeric ferric sulfate,manganese dioxide and the manganese oxide,manganese oxide）,probe into its basic physical and chemical properties of soil（p H and Eh）,Fe and Mn element content,pore water and soil As（III）and As（V）,As always,and solid phase in soil As the changing rule of the form over time,discusses the typical manganese iron material of arsenic pollution in soil As the influence of the migration and transformation,Further pot experiments were conducted to investigate the effect of iron and manganese oxide on inhibiting rice enrichment of As.The thesis mainly obtains the following research results:The physical and chemical properties of pore water can be significantly affected by the addition of ferric material.The potential（Eh）in pore water under the treatment of different iron-bearing materials increased to different degrees compared with that without the application of observation agent（CK）.The change of 1.0%iron sulfate was the most obvious,which was 184m V after 45d cultivation.Iron is decomposed into Fe³⁺and Fe²⁺in the water body,and the combination with OH-ions in the water body will cause the p H of soil pore water to decrease.Iron material to add impact the total As content in pore water,compared with CK,the soil pore water under different iron material handling the total As concentrations are reduced to some extent,of which 1.0%1.0%ferric sulfate,ferrous sulfate,1.0%polymeric ferric sulfate,1.0%iron manganese acid treatment under the total As content reduced by 45.8%,38.7%,41.3%and 90%,respectively,showed that iron material inhibits flooded soil under the condition of solid phase As the reduction of release behavior;The contents of As（III）and As（V）in pore water treated with iron-bearing materials were significantly reduced compared with CK,among which,manganese ferrite had the most prominent reduction effect,with a decrease of 90%compared with CK.The effect of iron on the horological transformation of solid As in soil was investigated in detail.Iron material in the soil under the processing As the unstable state（obligate adsorption state and not obligate adsorption state）content decreased,As the steady state（iron manganese appreciation,crystalline iron appreciation state and amorphous appreciation state）,increased levels of the addition of ferrous material make higher Fe³⁺content of pore water,the As（III）oxide for the As（V）and compared with the reactions such As appreciation,therefore in the soil As unstable not obligate adsorption state and obligate adsorption state content decreased,the stability of the amorphous appreciation stat.2.)Exogenous addition of manganese oxide has little effect on the basic geophysicist properties of pore water.Manganese oxide is relatively stable in pore water,and does not separate a large number of Mn ions and affect the geophysicist properties of pore water.Manganese oxide added affect the total As content in pore water,compared with CK,the soil pore water under different manganese oxide processing the total As concentrations are reduced to some extent,1.0%manganese dioxide,1.0%of the manganese oxide,1.0%1.0%manganese,iron dioxide acid manganese processing under the total As content decline in more than 90%,shows that manganese oxide inhibits flooded soil under the condition of solid phase As the reduction of release behavior;The contents of As（III）and As（V）in pore water treated with manganese oxide decreased significantly compared with CK,among which manganese ferrite had the most prominent reduction effect,with a decrease of 90%compared with CK.Detailed explored the manganese oxide for the modal transformation of solid phase in soil As manganese oxide processing under the influence of the soil As the unstable state（obligate adsorption state and not obligate adsorption state）content decreased,As the steady state（iron manganese appreciation,crystalline iron appreciation state and amorphous appreciation state）,increased levels of manganese oxide to join that higher Mn content of pore water,As happens with Mn complex adsorption,adsorption oxidation by the amount of precipitation also increases accordingly,so As the stable state of content in soil increased3)Through the rice pot experiment showed that adding iron to the As contaminated soil acid manganese is advantageous to the resistance of rice to absorb the As,can effectively reduce the rice As content of different parts,reduce the As content in rice grains,improve the content of rice root iron film,of which 1.0%treatment under acid manganese iron under the roots As reduced 50.19%As a50.19%reduction in calm and sheath,leaf As reduce 54.58%;As decreased by51.21%in the shell part and 70.63%in the brown rice.