Removal of POPs pesticides from soil by thermal desorption and its effect on physic-chemical properties of the soil
热解吸对土壤中POPs农药的去除及土壤理化性质的影响

Soil sample collected from a POPs pesticide-contaminated site in Beijing was treated with thermal desorption to investigate the efficiency of POPs removal and cultivability of the treated soil.Both residues of compositions of DDTs/HCHs and change of physicochemical properties of the treated soil were examined at different temperatures.The results showed that thermal desorption could eliminate DDTs and HCHs in the soils effectively.Removal efficiencies of p,p′-DDE and α-HCH were affected by temperature more seriously than others.More than 97%、99% of ∑HCH and ∑DDT could be removed from soil at 310 ℃ and 340 ℃,respectively,and the residue met Standard of Soil Quality Assessment for Exhibition Sites,and the removal rate did not increase apparently thereafter.Changes of physicochemical properties of the soils after thermal desorption varied depending on the degree of thermal desorption temperatures.SOM and TN decreased from 0.78%,0.0352% to 0.14%,0.0107%,respectively;pH fluctuated from 7.80 to 8.25;CEC decreased from 7.87 mg/kg to 5.00 mg/kg.However,rapid available phosphorus increased significantly,from 7.59 mg/kg to 21.8 mg/kg.With optimum temperature,acceptable change of physicochemical properties of the treated soils can be obtained.These results suggest that thermal desorption is an effective method for POPs-contaminated soil treatment,and process with suitable temperature has less effects on physicochemical properties of the treated soil.Therefore,thermal desorption is potentially a green remediation technology.