| [Objective]Cadmium（Cd）pollution is a serious threat to agricultural production and ecological security,and has been paid more attention at domestic and international.Traditional methods for remediation of Cd contaminated soil are expensive and difficult to popularize.However,plant extraction technology is easy to operate and environmentally friendly,which can be used as an important means for remediation of Cd contaminated soil.In this study,phytoremediation was taken as the breakthrough point.Firstly,the plants suitable for Cd remediation were selected.On this basis,organic acids were applied to the simulated Cd contaminated soil to explore the effects of organic acids on the transformation of Cd Forms in soil,the accumulation of Cd in plants and the removal efficiency of Cd in soil The interaction between soil and soil.The purpose of this study was to reveal the phytoremediation effect of organic acids on Cd contaminated soil,and to provide reference for remediation of Cd contaminated soil and guarantee agricultural production.[Method]Hydroponic experiments and pot experiments were carried out in 2019 with Chinese cabbage,Solanum nigrum and cotton as materials to screen Cd tolerant plants.In the hydroponic experiment,six Cd concentration gradients（CK,T1,T2,T3,T4,T5）were set for the three plants,with a total of 18 treatments;in the pot experiment,three Cd pollution gradients(1 mg·kg-1（A1）,5 mg·kg-1（A5）,10 mg·kg-1（A10）were set for the three plants,with the natural soil as the control（CK）,with a total of 12 treatments.In 2020,the pot experiment of applying organic acid in root bag was carried out,and the experimental material was cabbage.In this experiment,natural soil（CK）and 5.36 mg·kg-1Cd contaminated soil（Cd）were used as control,and 7.5 mmol·kg-1citric acid（BC1）,15 mmol·kg-1citric acid（BC2）,7.5 mmol·kg-1oxalic acid（BO1）and 15 mmol·kg-1oxalic acid（BO2）were applied to Cd contaminated soil,respectively.[results]（1）In the hydroponic experiment,the growth of cotton was inhibited first under Cd stress,and its biomass decreased significantly by 9.5%～35.5%;both cabbage and Solanum nigrum had certain tolerance and Cd accumulation ability;the Cd accumulation of cabbage was the largest under 5 mg·L-1Cd treatment, reaching 205.90μg·Pot-1,and that of Solanum nigrum was the largest under 20 mg·L-1Cd treatment, reaching 67.73μg·Pot-1.（2）In the pot experiment,with the increase of exogenous Cd,the biomass of cotton and Solanum nigrum was significantly reduced by 20.98%～23.03%and 60.90%～71.92%,and the Cd content in the upper part of cabbage increased 3.47～13.17 times compared with the control.The Cd enrichment coefficient of the upper part was cabbage>Solanum nigrum>cotton,and all were greater than 1,and the highest Cd accumulation in the upper part of cabbage was 630.3μg·Pot-1,Among the three plants,the accumulation ability is the strongest,which can be used for the remediation of cadmium contaminated soil.（3）Compared with the control,the activities of catalase,urease and sucrase in rhizosphere and non rhizosphere soil were increased by 3.72%～17.73%,8.33%～38.89%and 74.58%～138%in the rhizosphere soil,and by 1.32%～4.33%,33.33%～57.78%and 78.02%～102%in the non rhizosphere soil,respectively;The content of acid soluble cadmium in rhizosphere and non rhizosphere soil increased by 9.0%～16.2%and 8.99%～13.48%,respectively.（4）Compared with Cd treatment,the total biomass of cabbage was significantly increased by 27.79%and 14.56%under BO1 and BO2 treatments;Compared with Cd treatment,BC1,BC2,BO1 and BO2 treatments,the total accumulation and soil Cd removal efficiency increased by 38.2%～131%and 38.24%～136%,respectively.[Conclusion]（1）Among the three plants,Cabbage has the strongest cadmium tolerance and accumulation ability,which is more suitable for remediation of cadmium contaminated soil.（2）The application of citric acid and oxalic acid could increase the content of soil organic matter and the activities of catalase,urease and sucrase;The pH value of soil was reduced and the transformation of residual cadmium to acid soluble cadmium was promoted.（3）Organic acid application alleviated the growth inhibition of Cd on cabbage,and significantly increased the Cd accumulation capacity of cabbage and the Cd removal efficiency of soil;The effect of oxalic acid treatment was stronger than that of citric acid treatment.The transformation ability of residual cadmium to acid soluble cadmium and the removal efficiency of cadmium in 15 mmol·kg-1oxalic acid treatment were the highest. |
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