蠡湖水环境综合整治工程实施前后水质及水生态差异

为探讨水环境综合治理工程措施对蠡湖水生态环境的改善效果,对工程实施前后蠡湖水生态环境的变化及趋势进行了分析. 结果表明,水环境综合治理工程实施后,蠡湖水质明显好转,水体中ρ(TN)、ρ(TP)、ρ(COD_Mn)和ρ(Chla)年均值显著下降(P<0.01),ρ(TN)、ρ(TP)、ρ(Chla)分别由综合治理前 (1992—2002年平均值) 的5.77、0.19 mg/L和59.90 μg/L降至综合治理后的3.13、0.13 mg/L和27.12 μg/L,ρ(COD_Mn)则由7.09 mg/L降至5.00 mg/L以下；表层沉积物中w(OM)、w(TN)和w(TP)分别由2001年的40.40、1.19、2.61 g/kg降至2012年的19.60、1.16、0.59 g/kg；2012年生态修复工程区内初步形成了一个水生植物较为完整的生态系统. 综合整治后,水质改善效果明显,但部分水体感观指标〔如ρ(TSS)、SD(透明度)〕改善效果不明显,底栖动物优势种群仍为耐污种,生态系统完全恢复还需时日. 因此,有必要进一步开展以提高透明度、恢复沉水植物为核心的生态优化调控,促进蠡湖由藻型浊水稳态向草型清水稳态转变. 

Change in Water Quality and Ecosystem of Lihu Lake before and after Comprehensive Water Environmental Improvement Measures

To study the effects of comprehensive water environmental improvement measures on the aquatic ecological environment of Lihu Lake, changes and trends of the aquatic ecological environment before and after the measures were analyzed. Results showed that the water quality of Lihu Lake was remarkably improved, with the annual values of ρ(TN), ρ(TP), ρ(COD_Mn) and ρ(Chla) decreased significantly (P<0.01). ρ(TN), ρ(TP) and ρ(Chla) dropped from 5.77,0.19 mg/L and 59.90 μg/L, mean values in 1992-2002, to 3.13,0.13 mg/L and 27.12 μg/L,respectively, and ρ(COD_Mn) dropped from 7.09 mg/L to below 5.00 mg/L. The values of w(OM), w(TN) and w(TP) in the surface sediments decreased from 40.40 g/kg, 1.19 and 2.61 mg/kg in 2001 to 19.60 g/kg, 1.16 and 0.59 mg/kg in 2012, respectively. An entire ecosystem with aquatic macrophytes was set up in the ecosystem restoration areas in 2012. The effect of the projects on improving water quality was obvious after the improvements. However, some water sensory indicators, such as suspended particulate matter and transparency, did not change much, and tolerant species were still the dominant species of benthic animals. A full recovery for the ecosystem of Lihu Lake is still needed. Therefore, ecological optimization regulation focusing on increasing transparency and recovering submerged macrophytes must be further developed to accelerate the change in the stable state of Lihu Lake from algae-dominated turbid water to macrophytes-dominated clear water.