蓝藻水华暴发期间太湖贡湖湾某水厂水源水及出厂水中微囊藻毒素污染分析及健康风险评价

水体富营养化导致的有害蓝藻水华仍是目前全世界普遍面临的水环境问题,而有害蓝藻水华所引起的饮用水安全问题亦受到人们的广泛关注.为了解太湖水源地水源水及自来水厂出厂饮用水中微囊藻毒素(MCs)的污染现状,于2014年8月期间对贡湖湾某水厂水源水及出厂水中浮游植物胞内及胞外MCs浓度进行了调查,并同时检测了相关的理化指标.结果表明,水源水中胞内MCs总浓度平均值为7165.5 ng/L,以MC-LR和MC-RR为主,平均浓度分别为3408.7和3398.8 ng/L,其中MC-RR占总MCs比例的平均值为56.1%;而胞外溶解性MCs浓度相对较低,平均浓度为142.6 ng/L,最高浓度仅为512.8 ng/L.水厂出厂水中胞内MCs的检出浓度(平均值为0.77 ng/L)和检出频率都很低,去除率达99.8%以上;而胞外溶解性MCs的检出浓度(平均值为21.71 ng/L)和检出频率相对较高,但浓度仍远低于国家标准1.0μg/L,其去除率相对较低,仅为62.9%~81.8%.数据分析发现,水源水中胞内与胞外MCs浓度之间呈显著正相关,胞内MCs浓度与总氮(TN)浓度、铵态氮(NH+4-N)浓度、总磷(TP)浓度、高锰酸盐指数(CODMn)和浊度呈显著相关,而胞外MCs浓度与TN浓度、TP浓度、CODMn、浊度和叶绿素a浓度呈显著正相关;逐步回归结果显示,TP对胞内MCs浓度变化的解释率最高,而胞外MCs浓度变化主要与胞内MCs浓度相关.最终,通过对出厂饮用水中MCs浓度非致癌风险指数的计算发现,出厂饮用水对人类健康的威胁较小,但致癌风险相对较高.

Temporal microcystin dynamics of the source water and finished water in a waterworks of Lake Taihu

Harmful cyanobacteria blooms, which are caused by water eutrophication, is still one of the serious water environment problems encountered by the whole world. In order to estimate the current status of microcystins (MCs) in the source water and finished water of Lake Taihu, we examined the concentrations of intracellular MC (intraMCs) and extracellular MC (extraMCs) and related physiochemical parameters of the source water and finished water in a waterworks in August 2014. Our results showed that the mean concentration of intraMCs in the source water was 7165.5 ng/L, dominated by MC-LR and MC-RR, with the mean concentration of 3408.7 and 3398.8 ng/L, respectively, and MC-RR accounted for 56.1% of the total MCs. The extraMCs in the source water were still on a low level with the mean and maximum value of 142.6 and 512.8 ng/L, respectively. However, the concentrations of intraMCs in finished water were relatively on a low level (mean value of 0.77 ng/L) with the removal efficiency above 99.98%. Although extraMCs in finished water were also detected on a low level (mean value of 21.71 ng/L), the concentration and detection frequencies of extraMCs were significantly higher than those of intraMCs with removal efficiency of 62.9%-81.8%. Data analysis showed that the significant and positive correlation was observed between concentrations of intraMCs and extraMCs in source water. Meanwhile, intraMCs were significantly correlated with total nitrogen (TN), ammonium (NH₄⁺-N), total phosphorus (TP), chemical oxygen demand (COD_Mn) and turbidity, while extraMCs were significantly and positively correlated with TN, TP, COD_Mn, turbidity and chlorophyll-a. In addition, according to stepwise multiple linear regression analysis, TP could explain most of the variance of intraMCs in source water, while the variations of extraMCs could be primarily explained by intraMCs. Finally, according to non-carcinogenic risk index, MCs in finished water presented a relative low threat to the people there, while the risks will be higher when considering carcinogenic risk.