青狮潭库区沉积物/稻田土壤中有机氯农药残留与释放规律

The residue and release pattern of organochlorine pesticides in sediments and paddy soils in the Qingshitan reservoir region in Guilin, China

为了解青狮潭库区沉积物和土壤中有机氯农药(OCPs)残留及其释放特征,采用气相色谱法(GC-ECD)测定了青狮潭库区水库沉积物、池塘沉积物、河流沉积物和稻田土壤中OCPs含量,并运用室内模拟装置探讨了沉积物和稻田土壤在静置和悬浮两种情景下OCPs的释放规律。结果表明:水库沉积物、池塘沉积物、河流沉积物和稻田土壤中总OCPs残留量分别为81.55、88.60、68.96 ng·g^-1和92.62 ng·g^-1(干质量)。HCHs和DDTs是两类残留量较高的OCPs,其含量分别达到23.26~39.89 ng·g^-1和12.22~17.20 ng·g^-1。上覆水为超纯水时,静置组与扰动组的底物中OCPs向上覆水释放表现出先快后慢的特征,且扰动组的底物中OCPs释放量明显多于静置组;其中HCHs和β-硫丹的释放量最高。OCPs的理化性质、底物组成特征和外力扰动使各种OCPs在上覆水中的检出率和检出浓度存在明显差异,其中稻田土壤中OCPs向上覆水释放量最高而河流沉积物中OCPs向上覆水释放量最低。十二烷基硫酸钠可使底物中的OCPs快速向上覆水中释放(尤其促进了DDTs的释放),在扰动和静置情形下,上覆水OCPs浓度最少可提升134.44%和118.41%。因此,外界扰动和十二烷基硫酸钠汇入均可促进底物中OCPs的溶出释放。

In order to understand the residues and release characteristics of organochlorine pesticides(OCPs)in sediments and soils in the Qingshitan reservoir region, the concentrations of OCPs in the sediments of reservoir, pond, river and paddy soils are determined by a gas chromatography–election capture detector(GC-ECD). Under static and suspended conditions, the release patterns of OCPs in sediments and paddy soils are investigated using an indoor simulation device. The results show that the residues of OCPs in the sediments of reservoir,pond, river and paddy soils are 81.55, 88.60, 68.96 ng·g^-1 and 92.62 ng·g^-1(dry weight), respectively. Among all the OCPs, the concentrations of DDTs and HCHs are found to be at higher levels, being 23.26~39.89 ng·g^-1 and 12.22~17.20 ng·g^-1, respectively. When the overlying water is ultrapure water, the OCPs initially release quickly and then slowly in the static group and suspended group. The concentration of OCPs in the suspended group is found to be significantly higher than that in the static group. The release of HCHs and β-endosulfan is the highest. The physical and chemical properties of OCPs, substrate compositions and external disturbance results in significant differences in the detection rate and concentration of OCPs in the overlying water. The release rate of OCPs from paddy soils to overlying water is the highest, while the river sediments show the lowest release rate. Sodium dodecyl sulfate(SDS)can help OCPs in the substrate release into the overlying water quickly, especially for the DDTs. Under static and suspended conditions, the concentrations of OCPs in the overlying water increase by 134.44% and 118.41%, respectively. Therefore, both external disturbance and sodium dodecyl sulfate can promote the release of OCPs from the substrate to overlying water.