天津郊区土壤与作物中有机氯农药残留现状与来源初析

通过在天津塘沽和宁河地区野外实地采样分析,了解研究区域有机氯农药各异构体在土壤及作物各部位的残留水平,并通过特征比值推测其来源。结果表明,塘沽和宁河地区土壤中六六六的残留浓度均值分别为88.76μg·kg^-1与98.46μg·kg^-1,β-HCH占绝对优势而γ-HCH均未在土壤样品中检出,α-HCH手性分析结果显示为非消旋体,均表明土壤中六六六来自历史残留而非新近输入或林丹的使用。塘沽和宁河地区滴滴涕的残留浓度均值分别为30.87μg·kg^-1与1.30μg·kg^-1,亦来自历史残留,在个别点位可能曾使用过三氯杀螨醇。作物样品中六六六与滴滴涕的含量较高,经对数变换的生物富集系数变化范围分别为0.24～0.73与2.02～2.90。六氯苯、七氯、艾氏剂、异艾氏剂、反式氯丹、顺式氯丹、狄氏剂与异狄氏剂在大部分土壤与作物样品中也有不同程度的检出。

Residual Levels and Chiral Signatures of Organochlorine Pesticides in Soil and Plants in Tianjin,China

Residual level and enantiomeric composition of organochlorine pesticides（OCPs）,including Hexachlorobenzene,Heptachlor,Aldrin,Isodrin,trans-chlordane,cis-Chlordane,Dieldrin,Endrin,Dichlorodiphenyl trichloroethane（DDT） and Hexachlorocyclohexane（HCH） in soil and plant samples from Tanggu and Ninghe in Tianjin,China were analyzed by GC/ECD. The results showed most of the OCPs were detectable in these samples. Mean levels of ∑HCHs in soil were 88.76 μg·kg^-1 in Tanggu and 98.46 μg·kg^-1 in Ninghe,respectively. The composition of β-HCH was in strongly dominated,accounting for 91.9%-99.9% of HCHs,and γ-HCH was undetected in soil samples,which suggested that source of HCHs was from historic residue but not recent input of technical HCHs or lindane. Average concentrations of ∑DDTs in soil were 30.87 μg·kg^-1 in Tanggu and 1.30 μg·kg^-1 in Ninghe. Metabolites of DDT（DDE＋DDD） accounted more than 50% in all the samples and the ratio of o,p＇-DDT and p,p＇-DDT was higher than that in technical DDTs in samples from Tanggu,which implied that the residue of DDTs originated from historical usage of both dicofol-type DDT and technical DDT rather than new input. Besides isomer ratios,enantiomer ratio（ER） of chiral compounds could also provide helpful information about whether it was being currently applied or residue from past application. ER=1 meaned new input of parent chiral compound,and no metabolism had occurred. α-HCH displayed the non-racemic signatures in all samples,also indicating the old source with the usage of technical HCHs,suggesting the effectively management for restricting the application of HCHs and DDTs. Accumulation by plants was an important step for OCPs into the food chains. In this study,the accumulative abilities,expressed as logarithmic transformed bioconcentration factor（lg BCF） ranged from 0.24 to 0.73 for HCH and 2.02 to 2.90 for DDT,respectively. It was noticeable that the concentration of Dieldrin in Tanggu was obviously higher,that needed additional work to find its source. The levels of other organochlorine pesticides were within the ranges reported in other literatures.