贵州草海重污染区生态修复水质效果评估

对比分析贵州草海重污染湖区沉水植物生态修复区与对照区沉积物内源磷释放通量，探讨外源负荷得到有效控制后草海重污染区沉水植物生态修复效果，为草海综合污染治理与生态恢复提供一定的数据支撑和科学依据。2018年在草海修复区内和对照区各布设3个采样点， 10月至次年10月每个月分别对修复区和对照区水质开展连续跟踪监测。利用薄膜梯度扩散技术（DGT）对比分析了修复区和对照区内源磷释放通量，综合评估了草海重污染区生态修复效果。结果表明，沉水植物修复工程实施一年后，修复区水体氨氮（NH3-N）、总磷（TP）和溶解活性磷（SRP）浓度分别降低为对照区的65%、42%和67%。修复区沉水植物生长茂盛，水体DO含量稳定在8 mg/L以上，透明度显著提高，水质明显改善，CODMn 、NH3-N、TP浓度分别降低至5.7、0.39 、0.05 mg/L，达到地表水Ⅲ类标准。生态修复工程对内源磷释放量削减30% 以上，修复区内源磷贡献率38%，远低于对照区（74%）。当草海流域外源污染得到有效控制后，沉水植物生态系统恢复成为重污染区内源污染控制与水环境修复有效的手段。

Improvement of Water Quality by Ecological Restoration in Heavily Polluted Area of Caohai Lake, Guizhou Province

Caohai Lake is a typical grass-type shallow lake with abundant submerged plants. However, submerged macrophytes are nearly absent in the heavily polluted areas due to high nutrient concentrations (nitrogen and phosphorus). As a result, an ecological restoration project to replenish submerged macrophytes was conducted in a heavily polluted area of the lake. To assess project effectiveness, water quality was monitored for a year (October 2018 to October 2019) in the restored area and in a control area. Three sampling sites were located in each area and the following parameters were measured: dissolved oxygen (DO), pH and transparency; total phosphorus (TP) in the overlying water and sediment interstitial water; soluble reactive phosphorus (SRP), ammonia nitrogen (NH3-N) and CODMn of lake water samples; the release?flux of internal phosphorus using the diffusive gradient in thin films (DGT) method. Water quality in September 2018 was used as the baseline. Based on the monitoring results, we compared the release?flux of internal phosphorus in the restoration area with the control area, and assessed the effectiveness of restoring the submerged macrophytes. The project objective was to provide assessment data on the ecological restoration in Caohai Lake. One year after the restoration project was initiated, the concentrations of NH3-N, TP, and SRP in the restoration area were reduced, respectively, to 65%, 42%, and 67% of those in the control area. The newly introduced submerged macrophytes clearly enhanced water quality in the restored area of the lake. Dissolved oxygen in the lake increased and remained above 8 mg·L-1 and water transparency also improved. The concentrations of CODMn, NH3-N and TP decreased to 5.7 mg/L, 0.39mg/L and 0.05mg/L, respectively, meeting Grade III standards for surface water. The release flux of internal?phosphorus in the restoration area decreased by more than 30%, and the contribution of internal phosphorus to the TP of overlaying water was 38%, much lower than that in the control area (74%). After nutrient loading to Caohai Lake basin is better controlled, restoration of submerged plants is an effective measure for reducing endogenous nutrient inputs and improves water quality in lakes that have been heavily polluted.