挖掘扰动对污染场地空气中六六六、滴滴涕分布的影响

以某废弃有机氯农药厂污染场地的修复过程为对象,应用被动空气采样技术研究了挖掘扰动对污染场地及周边区域空气中ρ(HCHs)(HCHs为六六六)、ρ(DDTs)(DDTs为滴滴涕)分布的影响. 结果表明:在挖掘扰动过程中污染场地及周边空气中ρ(HCHs)和ρ(DDTs)显著增加,其中污染场地挖掘区空气中ρ(HCHs)和ρ(DDTs)抬升最大, ρ(HCHs)为23.36~494.39 ng/m3,平均值为(141.54±114.54)ng/m3；ρ(DDTs)为14.78~539.09ng/m3,平均值为(201.69±143.88)ng/m3. 居民区空气中ρ(HCHs)和ρ(DDTs)抬升最小, ρ(HCHs)为(4.36~29.00 ng/m3),平均值为(13.59±7.75)ng/m3;ρ(DDTs)为3.03~42.88 ng/m3,平均值为(13.37±11.53)ng/m3. 挖掘扰动增强了空气流动,使空气中扬尘增加,从而改变了空气中污染物单体的组成比例,其中β-HCH、δ-HCH、o,p′-DDT、p,p′-DDT所占比例升高,而其余单体所占比例降低. 空气中污染物ρ(HCHs)和ρ(DDTs)与温度呈正相关,与风速呈负相关. 因此,在对该类污染场地修复过程中,应该尽量避免在高温或强对流气候条件下挖掘施工,施工时应减少扬尘,以降低二次污染风险. 

Distribution Characteristics of HCHs and DDTs during Excavation of a Contaminated Site

Using passive samplers, the temporal variations of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were investigated during the excavation process of an abandoned pesticide-contaminated site. HCH and DDT concentrations in the air samples from the contaminated site and its surrounding area significantly increased with the excavation process. The HCH and DDT concentrations in the air samples were 23.36-494.39 ng/m3 (average 141.54±114.54) and 14.78-539.09 ng/m3 (average 201.69±143.88), respectively, with highest values in the core area of the excavation. The minimum values of the pollutants-HCH of 4.36-29.00 ng/m3 (average 13.59±7.75) and DDT of 3.03-42.88 ng/m3 (average 13.37±11.53) were found in the residential air samples. The monomer composition in the air changed during the excavation process; β-HCH, δ-HCH, o,p′-DDT and p,p′-DDT composition ratio increased. The HCH and DDT concentrations in the air samples were positively correlated with temperature, and negatively correlated with wind speed. Therefore, excavaion under high temperature or strong conrective weather conditions should be avoid to reduce fugitive dust as possible, and decrease the risk of secondary pollution.