Efficacy of acetic acid leaching in removing heavy metals from soil and assessment of its effects on groundwater
In order to elucidate the efficiency of acetic acid leaching in the removal of heavy metals from soil and its environmental impacts,we conducted a soil column leaching experiment that simulates in-situ flushing.We assessed the efficacy of three acetic acid concentrations(0.8,1.0 mol·L-1,and 1.5 mol·L-1),and used four contaminated soils to assess the removal rate,downward migration characteristics,and changes in heavy metal speciation.The effects of acetic acid leaching on the main nutrient elements in soil were also investigated.The results showed that acetic acid leaching had a high removal efficiency for heavy metals in the acidic and slightly acid soils,particularly in the case of Cd,for which the removal rate reached 40%-60%at acetic acid concentrations of 1.0 mol·L-1 and higher.Comparatively,the removal of Pb,Cu,and Zn was relatively poor,at less than 20%.Acetic acid leaching mainly removed the exchangeable and reducible Cd from top-soil,which was partially retained in the 20-40 cm sub-soil layer.Leaching with acetic acid at 1.0 mol·L-1 had no significant effect on contents of the main nutrients in the top-soil(P<0.05),although the concentrations of Cd and Pb in the leachate were higher than the gradeⅣgroundwater standard limit.These results indicate that 1.0 mol·L-1 is the optimal acetic acid concentration for the leaching of soil Cd and could be used to effectively clean up slightly contaminated soils with Cd concentrations lower than 0.6 mg·kg-1.However,attention should be paid to the risk of groundwater pollution with Cd and Pb.In practice,of acetic acid leaching of contaminated soils should be combined with countermeasures such as sub-soil fixation.
heavy metalchemical leachingacetic acidchemical speciationgroundwater
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