热解吸对土壤中POPs农药的去除及土壤理化性质的影响

为探索土壤热解吸修复技术对POPs污染土壤的修复效果及修复后土壤可耕作性,选择北京某农药厂旧址的POPs农药污染土壤,研究了不同温度下热解吸处理后土壤中滴滴涕(DDTs)和六六六(HCHs)各组分的去除率以及土壤理化性质的变化。结果表明,热解吸修复技术可有效去除土壤中POPs农药,其中,p,p’-DDE与α-HCH组分去除率受热解吸温度的影响比其他组分更为明显。∑HCH与∑DDT在310℃、340℃时分别达到97%、99%的去除率,且此时土壤中的污染物含量低于我国《展览会用地土壤环境质量评价标准》,此后去除率受温度的影响不明显。热解吸温度对修复后土壤的理化性质有一定的影响,不同温度影响的程度各不相同,其中,有机质含量与全氮含量分别由0.78%、0.0352%降至0.14%、0.0107%;pH波动幅度较小,由7.80变至8.25;阳离子交换量变化存在波动,但呈整体下降趋势,由7.87 mg/kg降至5.00mg/kg;土壤中速效磷显著增加,由7.59 mg/kg升至21.8 mg/kg。而在最优温度条件下,土壤理化性质受热解吸温度的影响较小。由此可以说明,热解吸技术可以用于POPs污染土壤的修复,选择适当的热解吸温度对土壤的可耕作性影响有限,因而是一种潜在的绿色修复技术。

Removal of POPs pesticides from soil by thermal desorption and its effect on physic-chemical properties of the soil

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.