太湖胥口湾表层水和沉积物中多环芳烃的浓度水平及生态风险

The Contamination Levels of Polycyclic Aromatic Hydrocarbons in Surface Water and Sediments in Xukou Bay of Taihu Lake and the Associated Ecological Risk

多环芳烃(polycyclic aromatic hydrocarbons,PAHs)是环境中普遍存在的稠环类化合物,由于其对人体健康和生态环境产生较大危害,美国环保局将16种PAHs列为优先控制的污染物。PAHs也是太湖流域的主要污染物之一。作为华东地区的重要水系和水源地,研究太湖环境质量的变化对改善太湖流域水生生态系统和提高沿岸居民身体健康具有重要意义。论文研究了太湖胥口湾水域表层水和沉积物的PAHs。结果显示,表层水和沉积物的PAHs总浓度分别为7.2~83 ng·L^(-1)和66~620ng·g^(-1)干重;年均值为29 ng·L^(-1)和218 ng·g^(-1)干重;年均毒性当量浓度为2.4 ng·L^(-1)和28 ng·g^(-1)干重。沉积物中的主要污染物为荧蒽、芘和,影响毒性当量浓度的主要是苯并(a)芘和二苯并(a,h)蒽。4环PAHs在沉积物中占主要,其浓度百分比为44%~48%,而5环PAHs则占毒性当量总浓度的90%以上,说明其危害主要来自5环PAHs。PAHs特征化合物比值分析表明,胥口湾沉积物中PAHs主要来源于煤和木材燃烧,表层水大部分为燃烧和石油的混合来源。污染水平的时空变化特点为丰水期(8月)表层水PAHs浓度偏高,沉积物偏低。湖区和湖岸的PAHs浓度只在丰水期有显著差异,表层水PAHs浓度湖区高于湖岸,沉积物相反;其他时期湖区和湖岸PAHs浓度无显著差异。根据加拿大沉积物环境质量标准,胥口湾整体生态风险水平较低。从时空分布特征来看,个别生态风险较高的点主要分布在湖岸,5月平水期可能是沉积物中PAHs生态风险较高的频发期。

Polycyclic aromatic hydrocarbons（PAHs）, a class of condensed ring compounds, are widely detected invarious environmental matrices. Because of their adverse effects on human health and ecological environment, 16 PAHs were listed as priority controlled pollutants by the United States Environmental Protection Agency. Studies showed that PAHs were the main contaminants in Taihu Lake. It is important to investigate the quality of water in Taihu Lake where is an important hydrographic net and urban drinking water supply in East China. The investigation is also very important to improve the aquatic ecosystem qualities and human health of the coastal residents. In the present study, the spatial and temporal variations of PAHs in surface water and sediments in Xukou Bay, Taihu Lake,were investigated. The results showed that the total concentrations of PAHs ranged from 7.2 to 83 ng·L-1for surface water, and from 66 to 620 ng·g-1dry weight for sediments. The average annual concentrations of PAHs in the two matrices were 29 ng·g-1and 218 ng·g-1dry weight, respectively. The mean benzo（a）pyrene toxicity equivalent concentrations（Ba Peq） were 2.4 ng·g-1and 28 ng·g-1dry weight in them, respectively. The main pollutants were fluoranthene, pyrene, and chrysene in sediments, while benzo（a）pyrene and dibenz（a,h）anthracene were the most abundant compounds when Ba Peqwas considered. The concentrations of 4-ring PAHs accounted for 44% ～48% of the total PAHs in sediments, and 5-ring compounds contributed to more than 90% of the total Ba Peq. The ratio analysis of the characteristic PAHs showed that PAHs in sediments in Xukou Bay are mainly from burning coal and wood, while PAHs in surface water mainly have fossil fuel and combustion sources. Relatively higher concentrations in surface water and lower concentrations in sediments were observed during the flood season（August）. There was no significant difference of the PAH contamination between dry season and ordinary level season. According to the Canadian sediment environmental quality standards, the ecological risks of PAHs in Xukou Bay were low. The spatial and temporal ecological risks showed that the locations with higher ecological risks were mainly at the nearshore. Higher ecological risks of PAHs in sediments might be observed during the ordinary level season（in May）, generally.