北江枯水期多环芳烃的污染分布特征与风险评估

Pollution distribution characteristics and risk assessment of polycyclic-aromatic hydrocarbons in surface water and sedment of Beijiang River

2016年12月北江清远段采集19个水和表层沉积物样品,采用气相色谱质谱(GC-MS)法测定了样品中的多环芳烃(PAHs),分析了枯水期北江水环境中PAHs的污染水平,并对生态风险进行了评价。结果表明,枯水期北江清远段水中PAHs浓度范围为41.2~413.8 ng·L-1,主要以二环芳烃和三环芳烃为主,与国内外已报道河流湖泊相比,北江清远段水中PAHs污染处于中等污染水平;沉积物中PAHs浓度范围为54.8~951.5 ng·g-1,以三环芳烃和四环芳烃为主,与国内外河流湖泊沉积物相比较,处于低污染水平。运用特征比值法对PAHs来源进行分析,北江清远段水和沉积物中枯水期PAHs污染来源主要由燃烧源所致,部分采样点存在混合源。通过计算终生致癌风险(ILCR)模型对北江清远段水体进行健康风险评价,结果表明,枯水期各采样点的致癌风险可忽略,婴幼儿的PAHs致癌风险高于青少年和成人。采用效应区间低、中值法(ERL/ERM)对枯水期表层沉积物中PAHs进行生态风险评价,个别点位表层沉积物中Dib超出ERL值,对生态环境潜在负面效应较小。

A total of 19 water and surface sediment samples were collected from the Qingyuan section of Beijiang River in December 2016,the polycyclic aromatic hydrocarbons(PAHs)in the samples were determined by GC-MS(gas chromatography-mass spectrometry).The pollution level of PAHs in the water environment of Beijiang River was analyzed and the ecological risk was evaluated.The result shows that PAHs concentration was ranged from 41.2 to 413.8 ng·L-1 mainly dicyclic and tricyclic aromatic hydrocarbons,which were in moderate pollution level compared with the reported rivers and lakes at home and abroad;PAHs concentration in sediments was ranged from 54.8 to 951.5 ng.g-1.Tricyclic and tetracyclic aromatic hydrocarbons are the main pollutants,which are at a lower pollution level compared with river and lakes sediments at home and abroad.The sources of PAHs in the Qingyuan section of Beijiang River were analyzed by the characteristic ratio method.The main pollution in the basin was caused by combustion sources,and mixed sources appeared in some sampling points.By calculating the lifetime carcinogenic risk(ILCR)model,the health risk of the Qingyuan section of the Beijiang River was evaluated.The carcinogenic risk of each sampling point in dry season can be neglected,and the carcinogenic risk of PAHs in infants was higher than that of adolescents and adults.The ecological risk assessment of PAHs in surface sediments was carried out by Effects Range Low and Effects Range Median(ERL/ERM)method.Dih,Ant and Dib in surface sediments at individual sites exceeded ERL values and had less potential negative effects on the ecological environment.