Study On The Process Of Straw Decomposition And The Adsorption And Desorption Of Antimony In Yellow Soil

China is one of the world's major antimony depositing and producing countries.The mining and smelting of antimony mine bro?ght serious pollution of soil,which is harmful to human health.China is an agricultural country with a large number of straws producing every year.Generally,the straw returning is a more environmentally friendly way to input the organic matter into the soil,which can cause significant environmental effects of soil elements.The rapid humification process will take place after straw returning to the field under suitable conditions,which will lead to the change of soil organic matter properties,thus affecting the migration and transformation of heavy metals.Therefore,the batch culture experiment(240 d)with the experiment group(adding 2%rice straw powder passing 100 mesh sieve)and the control group(without straw)were cultivated to explore the changes of p H value,organic matter,humic acid and theelement content(C,H,N)in yellow soil during straw humification.The optimum conditions of soils with the highest organic matter content(20 d)and the maximum p H value(40 d)during the middle stage(120 d)and the later stage(240 d)of growth after straw returning were used to explore the adsorption and desorption characteristics of Sb(V)in the soil.In order to understand the change of properties,the process of straw humification and the influence and mechanism of sb(?)adsorption and desorption in soil during the process of straw returning in yellow soil,some results are summarized as following:1.With the increase of culture time,the p H of soil in the experimental group increased firstly at the maximum value of 5.73 and then decreased,stablilizing between5.10 and 5.20.the p H of soil in the control group showed a downward trend,and finally stabilized between 4.80 and 4.90.The change trend of soil organic matter content in the experimental group and the control group all increased firstly,reached the maximum of36.36 g/kg and 29.51 g/kg after 20 days,and then decreased,and finally fluctuated up and down at 31.00 g/kg and 26.00 g/kg respectively.On the one hand,after 130d,the content of fulvic acid and humic acid increased by 0.72 g/kg and 0.32 g/kg respectively,and the total amount of humic acid increased by 1.04 g/kg.2.The degree of soil humification was increased,and the value of H/C in soil showed a downward trend,decreasing from 0.483 to 0.283 and 0.312 respectively in the experimental group and the control group.Beside,the degree of soil humification in the experimental group was higher than that in the control group.Compared with the initial soil,the content of C and N were increased in the experimental group,while the content of H did not change significantly.With the increase of culture time,the content of C and N in the experimental group and the control group increased and decreased,respectively.The content of H element in the experimental group and the control group decreased firstly and then increased slightly.3.The adsorption of antimony on soil can be divided into two stages:fast adsorption and slow adsorption.The fast adsorption was completed in the first 120minutes.In the experiment of adsorption kinetics,the p H of supernatant increased with the increase of adsorption time.The soil adsorption experiment basically reached equilibrium within 7 days.The decomposition of soil organic matter promoted the adsorption of Sb(V)which increased by 12%?21%compared with the initial soil adsorption amount in the experimention.Under the condition of 1mg/L concentration in this experiment,When the adsorption reached equilibrium,the adsorption amount of Sb(V)in the control group was slightly higher than that in the experimental group,but it was not obviously.in this experiment,the Elovich equation has the best fitting effect,and the R~2 is between 0.86 and 0.97.4.The best fitted theoretical model for the adsorption is Freundlich isotherm model,and the R~2 is above 0.947.The results of desorption experiment after isotherm adsorption in experimental group and control group showed that the desorption rate of Sb(V)was very low in soil,between 1%and 10%,and the lower the concentration of antimony solution,the higher the desorption rate was.5.In this experiment,Sb(V)complexed with the substances containing hydroxyl,carboxyl and carbonyl in the soil.