Effects Of Phosphoric-acid Modified Biochar Combined With Chlorine On Lead And Cadmium Adsorption In Wheat

In recent years,with the development of social economy,the problem of heavy metal pollution has been a worldwide problem.It is urgent to solve the problem of food security by repairing contaminated farmland.In order to find a way to control calcareous lead and cadmium contaminated soil,field experiments and pot experiments were conducted to study the effects of modified-biochar and different doses of potassium chloride and calcium chloride on the remediation of calcareous lead and cadmium contaminated soil.The main results are as follows:Field experiments:1.The application of modified biochar in calcareous cadmium contaminated farmland could increase the yield of wheat in the field,and the effect was significantly increased in the amount of 15 t·hm-2.The mixture of potassium chloride and potassium chloride could increase the yield of wheat in the field.2.Application of phosphoric-acid modified biochar can promote the reduction of DTPA lead in soil,and BCR was used to analyze the different forms of lead in soil,phosphoric-acid modified biochar can promote the transformation of strong and weak acid extracted and reduced lead into stable oxidation state and residual lead in soil.Combined application of potassium chloride can significantly promote this phenomenon.3.The application of modified-biochar in calcareous cadmium contaminated soil can reduce DTPA cadmium in soil.With the increase of application amount,the reduction effect is significant.It has a positive correlation with the cadmium content of wheat grain,and mixed potassium chloride can further reduce the cadmium content in field wheat grain.4.The application of modified biochar made the cadmium content in different parts of wheat decreased significantly.The total amount of lead in soil was 6.68 mg·kg-1,which did not reach the pollution level,the application of phosphoric-acid modified biochar can reduce the available lead in soil,and lead in wheat does not reach the detection level.The cadmium content in different parts of the distribution of wheat for grain < glume < stem leaf < root,compared with the control group,15 t·hm-2 modified activated carbon and potassium chloride mixed biological methods of wheat grain Cd decreased by 59.45%.Pot experiments:1.The application of modified biochar can increase the yield of single pot wheat,and with the increase of applied amount,the yield of wheat increased.The addition of chloride can further increase the yield of wheat,and the effect of high-dose chloride is more significant.Comparing different chloride,it was found that adding calcium chloride increased wheat yield more significantly.2.Phosphate modified biochar significantly reduced soil available Pb and Cd content,low doses of chlorine addition in promoting soil available Pb decreased at the same time,soil available cadmium also significantly decreased;and the addition of high doses of chlorine can promote soil available Pb decreased,but the available Cd in extent increased.3.Adding phosphate in calcareous soil polluted by lead and cadmium in modified biological carbon and chlorine can change the soil lead and cadmium speciation,the bioavailability of strong acid extractable,reducible Pb and Cd conversion to oxidized and insoluble fraction,helps to reduce the lead and cadmium accumulation in wheat the characteristics of grain.4.Calcareous soil with phosphate modified biochar and chloride fertilizers can significantly reduce the content of lead and cadmium in different parts of wheat;the modified biochar application rate of 100 g·kg-1 combined application of low dose Ca Cl2 can make the wheat grain lead decreased 88.73%,cadmium decreased 65.69%,the lead content of grain reduced to 0.16 mg·kg-1(in accordance with the "hygiene standards" food GB2715-2016).