南京市小河流表层沉积物中的有机氯农药残留及其分布现状

Residues and Distribution Character of Organochlorine Pesticides in Stream Sediments in Southwestern Suburb of Nanjing

2004年春,以南京市西南部4条通入长江的小河流为试区,采集不同断面表层沉积物和水样,以及相应流域内农田土壤样品,对所有样品中有机氯农药的残留及其分布状况进行研究,并讨论了农田土壤有机氯农药残留量和理化性质对河流表层沉积物中有机氯残留量的影响.结果表明:沉积物对水体HCHs和DDTs有明显的富集作用,不同河流富集状况不尽相同.农田土壤中HCHs与沉积物中HCHs残留量基本相近,土壤中DDTs残留量明显高于沉积物,可见土壤中HCHs更易迁移至水系.由于土壤有机质易于从偏碱性的土壤中淋出,吸附在有机质上的有机氯残留物易随之转移至沉积物中,因此在流经偏碱性土壤的河流沉积物中OCPs残留量较高.各流域内农田土壤与河水及沉积物中α/γ及DDE/DDT值的变化有一定程度的趋同性,反映了土壤是水体及沉积物中OCPs的主要来源.此外,有机氯各组分在土壤-水体-沉积物的迁移过程中,易迁移者在沉积物中含有较高比例.此外,沉降作用将大大降低小河流向长江输入的OCPs.

Sediments and water samples were collected from different cross sections Of 4 tributaries of Yangtze River in southwestern suburb of Nanjing city in spring 2004, and agricultural soil sample were collected also in those valleys. The residues and distribution of organochlorine pesticides in sediments from different streams were determined and the influence of soil character on organochlorine pesticides residues in sediments were studied. Result showed that accumulation of HCHs and DDTs occured significantly in the sediments and related to soll erosion. Residues of organochlorine pesticides in sediments may be influenced obviously by pH of agricultural soil in the valleys. In the alkaline soil, organic matters could be leached easily and entered the stream water and accumulated into sediments, resulting in accumulation of organochlorine pesticides adsorbed on soil organic matters in sediments. In the transfer process of materials from soil to water and sediment, constitutes of organochlorine pesticides in multiphase environmental medium were changed; usually those components easily leached from soils had higher residue levels in sediments. Meanwhile, sedimentation of soil in streams could reduce OCPs input to the Yangtze River.