Effects of Activator Additions on Soybean Growth and Their Cd Enrichments in Calcareous Soil
With advantages of resource recyclability,low-cost,low carbon emissions and environmental friendliness,phytoremediation is gradually replacing other methods for in situ treatment of heavy metal pollution in the soil.However,the low biological effectiveness of heavy metals in the calcareous soil limits the application of phytoremediation technology.In order to investigate the efficiency of activator-strengthened phytoremediation tech-nology on the remediation of heavy metal contamination in the calcareous soil,effects of different concentrations of activators such as oxalic acid,ethylenediaminetetraacetic acid(EDTA)and citric acid on the soybean growth and their Cd enrichments were investigated by pot culture tests using soybean as the model plant.Results show that the addition of low and medium concentrations of activators has no significant effect on the soybean growth,while high concentrations of activators can,to a certain extent,inhibit the germination,growth and nutrient accumulation of soybean.The addition of activators promotes the uptake of Cd by soybean,with the most significant promotion effect achieving via adding 1.0 μmol·g-1 of EDTA and 3.0 μmol·g-1 of oxalic acid,and the Cd removal rate is 3.99 and 3.96 times higher than those of control group,respectively.The addition of activators lowers the soil pH and chan-ges the form of Cd in the soil.The addition of oxalic acid and a low concentration of EDTA can convert Cd in the soil from a stable form to a plant-absorbable state,thus promoting the removal of Cd in the soil by soybeans,while the addition of citric acid can promote the root-to-stem transport of Cd and thus improve the removal of Cd by soy-bean.Results of the research provide a scientific reference for the application and promotion of phytoremediation techniques toward heavy metal contamination in the calcareous soil.
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