Migration And Transformation Of Chromium In Soil And Theinteraction Between Chromium And Seleniumits

Chromium(Cr)is one of the most common heavy metal pollutants in soil.Its adsorption characteristics and existence in soil determine its migration.In this paper,applying isotherm method adsorption of exogenous Cr were measured in cinnamon soil,fluvo-aquic soil and loessial soil.The effects of oscillation time and temperature on the adsorption were studied.The soil column leaching test was used to investigate the distribution,migration and morphological transformation of chromium in soil under different time.The growth,physiological characteristics and chromium absorption of eggplant were studied under different chromium levels(0,10,20,40,80 mg/kg)with different concentrations of selenium(12,24,48 mg/kg).The research conclusions were as follows:1.Adsorption equilibrium times and adsorption capacities for Cr were different for soil of different types and layers.The oscillation equilibrium time of the three tested soils was yellow loessal soil(16 h)fluvo-aquic soil(8 h),cinnamon soil(8 h).After 24 h,the adsorption capacity of the three tested soils showed fluvo-aquic soil > cinnamon soil > loessial soil.With the increasing of temperature,the amount of adsorption gradually decreased,and the rate of decline of different types of soils was different,which was characterized by fluvo-aquic soil > loessial soil > cinnamon soil.The isotherms of Cr adsorbed by different soil were consistent with the Freundlich equation and the Langmuir equation,and the Freundlich equation was better.2.Under leaching conditions,the migration and transformation of Cr were different in different types and different layer of soil.After 115 days,the Cr content of the remaining soil in the soil was different.It was mainly distributed in the surface layer of soil(0~20 cm)in cinnamon soil and fluvo-aquic soil,and mainly distributed in the bottom layer in loess soil(40~60 cm).The total residual rates of the three different soils were 4.96%,7.95%,and 3.43%,respectively,and the residual rate of fluvo-aquic soil was the largest.After leaching test had finished,the morphological distribution of the three tested soils was changed to a stable form,mainly composed of residual state and sulfide organic combination.Among them,the morphological transformation of fluvo-aquic soil was the smallest.During the leaching process,the risk of migration of fluvo-aquic soil was the lowest.3.The results of pot experiment showed that under the single Cr treatment,with the increasing of Cr concentration,the plant height,root length,shoot and shoot dry weight of eggplant were significantly inhibited,chlorophyll and soluble protein in leavesand the content of malondialdehyde(MDA)increased,and the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased first and then decreased.The results of Se-Cr mixed treatment showed that Se could alleviate Cr toxicity of eggplant.Under different Cr concentrations,the effect of different concentrations of Se was different.The plant height,root length and biomass of eggplant increased,and the Cr in plants decreased at 10,20,40,80 mg/kg of Cr,and at 12,24,48,48 mg/kg of Se.