DDT Vertical Migration and Formation of Accumulation Layer in Pesticide-Producing Sites

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• 作者：Li Liu ; Liping Bai ; Changgeng Man ; Wuhong Liang ; Fasheng Li ; Xiaoguang Meng
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：August 4, 2015
• 年：2015
• 卷：49
• 期：15
• 页码：9084-9091
• 全文大小：481K
• ISSN：1520-5851

文摘

Soil samples were collected at various depths (0.5鈥?1.5 m) from ten boreholes that were drilled with a SH-30 Model Rig, four of which were at a dicofol production site while six were at a dichlorodiphenyltrichloroethane (DDT) production site. In industrial sites, the shallow soils at depths of 0鈥? m were mostly backfill soils, which cannot represent the contamination situation of the sites. The contaminated levels in the deep original soil can represent the situation in contaminated sites. All the soil samples investigated at the DDT and dicofol production sites were found to be seriously polluted. The contents of both DDT (0.6鈥?071 mg/kg) and dicofol (0.5鈥?440 mg/kg) were much higher at the dicofol production site than at the DDT production site (DDTs, 0.01鈥?64.6 mg/kg; dicofol, <0.1 mg/kg), even in the deep soil. DDTs had a different distribution in the soil of the pesticide production site from that in the soil outside the sites and that in agricultural soils. The results of the investigation revealed that DDTs were easily enriched in cohesive soil and in the bottom zone of aquifers, where the concentration was higher than in above the layers. DDTs were found to be hard to degrade, and their degradation speed was slower than their vertical migration, despite the fact that hydrophobic DDTs did not migrate easily in soils. In the dicofol production site, the value of DDE/DDD cannot indicate the degradation condition of DDTs, nor can the value of (DDE + DDD)/DDT identify how long DDTs have remained in the soil. It is debatable that the half-life of DDT inputted to soils is about 20鈥?0 years, maybe longer than the generally recognized time.