Effects of Biochar and Citric Acid on Calcareous Soil Cadmium Form Transformation and Cadmium Accumulation in Alfalfa
A pot experiment was conducted with cadmium(Cd)contaminated soil(7.15 mg/kg Cd)as substrate,and biochar prepared by different pyrolysis temperature(250 and 480℃)(B1 and B2),different dosage(1 and 10 mmol/kg)of citric acid(N1 and N2)and their combinations(B1N1,B1N2,B2N1,B2N2)were set with only planting alfalfa as control(CK).Their effects on soil properties,Cd form transfor-mation and Cd accumulation in alfalfa were studied.The results showed that both biochar and citric acid treat-ments could increase the content of soil available nutrients and the soil enzyme activities,and change the com-position of low molecular weight organic acids,and the effects of high-temperature pyrolysis biochar and high-dose citric acid treatment were more significant.Biochar and citric acid treatments affected the transformation of Cd form in soil and the enrichment of Cd in alfalfa,but their effect level and mechanism were different.The biochar with different pyrolysis temperatures had the adsorption passivation effect on Cd,while low concentra-tion of citric acid had slight passivation effect on Cd,and high concentration of citric acid activated soil car-bonate-bound Cd(CA-Cd)and exchangeable Cd(EX-Cd)to increase the effective Cd content.Under the combined application of biochar and citric acid,compared with CK,the soil available Cd content,plant Cd content and bioconcentration factor of B1N2 treatment were significantly increased by 40.01%,57.48%and 12.40%respectively,while those of B2N1 were significantly decreased by 26.79%,49.38%and 30.81%re-spectively.In summary,the effect level and mechanisms of biochar prepared by different pyrolysis tempera-tures and different doses of citric acid on Cd remediation were different.High-temperature biochar combined with low-dosage citric acid could passivate soil Cd,while low-temperature biochar combined with high-dosage citric acid could activate soil Cd and promote the Cd enrichment in alfalfa.
万方数据
维普
