Effects Of Three Kinds Of Organic Acids On Cd And Zn Contaminated Soil Restoration For Two Plants

The aim of this study was to evaluate the capacity of Euphorbia thymifolia L. and Bidens pilosa L. to absorb Cd and Zn in the polluted soil from a city in southern China. Under the treatment of exogenous citric acids,malic acids and oxlic acids. The effects of organic acids on Cd and Zn forms and soil environment quality were also studied.The main results are as follows:(1)The concentration of Cd and Zn in Euphorbia thymifolia L. reached 0.777 mg·kg-1 and 64.9 mg·kg-1 when the addition of malic acid were 16.5 mmol·kg-1 and 11.0 mmol·kg-1,respectively. The concentration of Zn in Bidens pilosa L. reached 136 mg·kg-1 when the addition of oxalic acid were 11.0 mmol·kg-1. Exogenous organic acids with certain amount help to remove heavy metals from the polluted soil by Bidens pilosa L. and Euphorbia thymifolia L.(2)Citric acid,malic acid and oxalic acid could increase the translocation factor of Cd for Euphorbia thymifolia L. and the translocation factor increased from 0.396 to 1 when addition of malic acid was 16.5 mmol·kg-1. The translocation factor of Cd for Bidens pilosa L. could reach above 1 with the maximum 1.49 when organic acids were added. Organic acids had no significant effect on the translocation factor of Zn for Euphorbia thymifolia L. Citric acid significantly decreased the translocation factor of Zn for Bidens pilosa L. while malic acid and oxalic acid increased the translocation factor of Zn.(3)The extractable Zn content increased by 3.24%-13.4% with the addition of organic acids. The concentration of Zn in Euphorbia thymifolia L. and Bidens pilosa L. had significance positive correlation with the extractable Zn content with correlation coefficients 0.448 and 0.664, respectively.(4)The microbial activity, urease activity and sucrase activity in soil increased with organic acids added. The concentration of Lipid-P increased from 6.29μg·kg-1 in the control to 13.2μg·kg-1, and the urease activity and sucrase activity increased from 0.157 mg·kg-1·h-1 to 0.262 mg·kg-1·h-1 and 1.36 g·kg-1·h-1 to 1.90 g·kg-1·h-1 respectively.