广州南沙红树林湿地水体和沉积物中有机氯农药的残留特征

红树林湿地对保护海岸生态环境起着重要作用,为研究有机氯农药(OCPs)在广州南沙红树林湿地水体和沉积物中的残留水平、来源和生态风险,于2015年3月采集该地区10个表层水体样品和7个表层沉积物样品,并采用GC-ECD测定其中OCPs的含量.结果表明,水体中OCPs含量为1.89~90.19 ng·L~(-1),平均值为30.16 ng·L~(-1);沉积物中OCPs含量为3.10~16.02 ng·g~(-1),平均值为8.58 ng·g~(-1).与其他河口、海湾地区相比,研究区有机氯农药污染处于中等水平.研究区水体和沉积物间HCHs和DDTs的分配系数平均值分别为857和368;在分配系数较高的区域,沉积物成为水体二次污染源的潜力较大.来源分析表明,研究区水体和沉积物中近期仍存在HCHs和DDTs输入,HCHs主要来源于林丹的使用,DDTs来源于三氯杀螨醇与工业DDT的混合输入;与水体相比,沉积物中的OCPs可能包含更多历史残留组分.风险评价结果显示,水体中OCPs的生态风险较小,但沉积物中OCPs存在较高的生态风险,可能危害红树林生态系统.

Residues of Organochlorine Pesticides (OCPs) in Water and Sediments from Nansha Mangrove Wetland

Mangrove wetland plays an important role in coastal environment. A total of 10 surface water samples and 7 surface sediments samples were collected in March, 2015 from Nansha mangrove wetland, and 8 compounds of organochlorine pesticides (OCPs) were determined by GC-ECD to investigate residues level, source, and ecological risk of these compounds in the study region. The result showed concentrations of OCPs in water ranged from 1.89 to 90.19 ng·L^-1 (mean 30.16 ng·L^-1), and concentrations of OCPs in sediments varied from 3.10 to 16.02 ng·g^-1 (average 8.58 ng·g^-1). Compared with other estuaries and harbors around the world, concentrations of OCPs in this study stayed at a median pollution level. The mean values of distribution coefficient of HCHs and DDTs between water and sediments were 857 and 368, respectively. Sediments in some parts of the area, whose distribution coefficient was relatively high, may bring water the secondary pollution. Source analysis indicated that HCHs mainly originated from the application of Lindane, and DDTs originated from mixed sources of dicofol and technical DDT. Compared with OCPs in water, OCPs in sediments might contain more historical residual components. OCPs in water had light ecological risk, but OCPs in sediments posed a potential high risk to mangrove ecosystem.