嵌入式水库在饮用水源水质提升和水生态保护中的作用及风险分析

Function and Risk Analysis of Embedded Reservoir in Water Quality Upgrading and Water Ecological Protection for Drinking Water Sources

为探讨嵌入式水源水库在水源品质提升和生态健康保障中的作用及潜在的生态风险,以东太湖中嵌入式水源水库为研究对象,于2018年9月—2019年8月对该水库内外水质和浮游植物群落进行综合调查分析。通过对比分析,揭示了水库内外水质和浮游植物群落结构差异。结果表明:嵌入式水源水库内水质得到明显提升,TP、TN和Chl-a浓度分别下降16.9%、33.3%、32.6%,透明度提升48.3%;综合营养指数(TSI)库内为50.25,相较于库外的65.1明显下降,营养状态得到显著改善。原水进入水库后,藻类密度从3.13×10^(7)cell/L显著下降到2.32×10^(7)cell/L(p<0.05);蓝藻仍然占优,但总体相对丰度从74.1%下降到52.4%。通过前置湿地净化和增加水力停留时间提升水质和水生态健康状况,通过物理沉降、水生植物吸收等作用有效降低原水体氮、磷含量,对微污染水源水有较好的净化作用。但是,该水库仍存在一定的生态风险,如冬季候鸟导致的水体营养盐升高和水体流动性下降导致的产嗅丝状蓝藻大量繁殖的问题,应制定有效的对策(如利用生态湿地强化净化效果和增加水体流动性等手段)防范潜在的风险。

To explore the role of embedded water resource in upgrading water quality and its potential water ecological risk,taking embedded water source reservoir in East Taihu Lake as the research object,water quality and phytoplankton communities inside and outside the reservoir were investigated from September 2018 to August 2019.Through comparative analysis,differences of water quality and phytoplankton community structure inside and outside the reservoir were revealed.The results showed that water quality in embedded water source was significantly upgrading,concentration of TP,TN and Chl-a decreased by 16.9%,33.3%,and 32.6%,respectively,and transparency increased by 48.3%.Average trophic state index(TSI)was 50.25(inside),far less than 65.1(outside),and trophic state inside the reservoir was significantly improved.The algae density decreased significantly from 3.13×10^(7 )cell/L to 2.32×10^(7) cell/L(p<0.05)after the raw water entering the reservoir,and Cyanobacteria were still dominant,while the relative abundance decreased from 74.1%to 52.4%.Embedded reservoir mainly improved water quality and water ecological health by pre-wetland purification and increasing hydraulic retention time(HRT),and the nitrogen and phosphorus content of raw water were effectively reduced by physical sedimentation and aquatic plant absorption,which showed a good purification effect on the slightly polluted water source of the embedded reservoir.However,there were still some water ecological risks in the reservoir,such as the increase of nutrients caused by migratory birds in winter and large scale reproduction of odor-producing algae caused by the decline of water mobility.Effective measures should be formulated in the future in order to prevent potential risks,such as using wetland to enhance purification effect and water mobility.