岩溶地下河流域表层土壤有机氯农药分布特征及来源分析

为研究有机氯农药(OCPs)在重庆南山老龙洞地下河流域表土中的分布趋势、组成特征、来源及污染水平,采用气相色谱-微池电子捕获检测器(GC-μECD)分析了6个代表性表层土样中20种OCPs.结果表明,研究区表层土壤中20种OCPs均有不同程度检出,其中(除DDE、顺式氯丹、反式氯丹、狄氏剂)16种检出率高达100%,氯丹类和DDTs是主要污染物,不同采样点有机氯农药含量差异较大.OCPs总量变化范围在5.57~2 618.57 ng·g~(-1)之间,平均值为467.28 ng·g~(-1),与国内外其它区域相比,研究区表层土壤中HCHs和DDTs含量处于中上水平.有机氯农药总量和HCHs、DDTs、氯丹类农药总量分布具有相似的空间变化趋势,均为:上游中游下游,并且上游与中、下游的差距尤为显著.来源分析表明,HCHs主要来源于林丹的使用,DDTs既来源于历史农药残留,也来源于近期工业DDT的非法使用和三氯杀螨醇的输入,氯丹主要来自历史残留和大气沉降.结合中外土壤质量标准,新力村土壤属于有机氯农药严重污染土壤,下龙井湾、夏家咀和赵家院子土壤受到有机氯农药轻度污染,龙井旁和高中寺土壤属于无污染土壤.

Distribution Characteristics and Source Identification of Organochlorine Pesticides in Surface Soil in Karst Underground River Basin

Six typical surface soil samples were taken in Laolongdong underground river basin, and 20 OCPs were analyzed by gas chromatography equipped with micro-⁶³Ni electron capture detector. The purpose of this study was to investigate the distribution, composition and source of organochlorine pesticides (OCPs) in the surface soil of Laolongdong underground river basin, and to further evaluate the pollution level. The results showed that 20 OCPs were inordinately detected in the soil samples and the detection rate of 16 OCPs (except for p,p'-DDE, cis-Chlordane, trans-Chlordane, dieldrin) was 100%. Moreover, the CHLs and DDTs were the main contaminants, and there were obvious differences in the concentrations of organochlorine pesticides between different sampling points. The concentration range of total OCPs was 5.57-2618.57 ng ·g^-1 with a mean of 467.28 ng ·g^-1. Compared with other regions both at home and abroad, the concentrations of HCHs and DDTs in the surface soil samples of the studied area were arranged from high to middle levels. The total concentrations of OCPs, HCHs, DDTs and CHLs had a similar variation tendency in spatial distribution, upstream > midstream > downstream, and the concentrations of OCPs in upstream were obviously higher than those in midstream and downstream. Source analysis indicated that the HCHs mainly came from the use of lindane. DDTs in soil came from not only the early residues but also recently illegal use of industrial DDTs and the input of dicofol. In addition, chlordan was mainly from the early residues and atmospheric deposition. Compared with the Environmental Quality Standard for Soils of China and Netherlands, the level of OCPs in Xinli vilage soil was categorized as highly polluted, but the levels of OCPs in Longjing bay, Xia spit, and Zhao courtyard soils were classified as slightly polluted, while the Longjing adjacency and gaozhong temple soils belonged to unpolluted ones.