Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China; Huaian Surveying and Design Institute of Water Resources Co., Ltd., Nanjing 211102, China.
Donghu Experimental Station of Lake Ecosystems, State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, The Chinese Academy of Sciences, Wuhan 430072, China.
Sci Total Environ. 2018 Jun 1;625:1433-1445. doi: 10.1016/j.scitotenv.2018.01.008. Epub 2018 Jan 12.
The geo-engineering approach of modified soil flocculation has been widely applied to mitigate algal blooms and eutrophication in relatively small lakes. Nevertheless, its potential ecological risks and feasibility should be examined and identified prior to its application in large natural lakes given the multiple functions of these water bodies in human health and welfare. In situ mesocosm experiments on modified soil flocculation were performed in Lake Taihu during summer 2010 and 2011. Chitosan-modified kaolinite (CMK) soil was used to flocculate algal blooms and improve water transparency to facilitate the re-establishment of the submersed macrophyte Vallisneria natans in this shallow eutrophic lake. Moreover, the ecological effects of CMK soil were assessed. Results showed that repeated additions of CMK (0.3g/L for each time) improved water quality in terms of Chl-a, TN, and TP concentrations; TN/TP ratio; turbidity; redox conditions; and nitrification and denitrification activities. These effects lasted for 48days. After the fourth dose of CMK, the biomass of all phytoplankton categories, except for that of Cryptophyta, decreased by >90% (ca. 1-2×10cell/L or 0.38-0.55mg/L of wet weight). Zooplankton biomass markedly decreased after the first CMK addition, and copepods became dominant. These effects, however, did not last for the long term. Most importantly, submersed V. natans was restored successfully when water clarity and quality were improved through repeated CMK flocculation. Nevertheless, the indices of carbohydrate depletion and free amino acid accumulation indicated that the plant experienced physiological stresses. The reestablishment of V. natans reinforced the positive effects of repeated CMK dosing on water quality, and promoted a clear water state. V. natans is recommended for vegetative restoration in shallow eutrophic lakes given its facile transplantation, high stress tolerance, and physiological traits, which can be applied as indices of post-flocculation effects. In summary, the combination of repeated CMK dosing and revegetation of V. natans can feasibly improve water quality and initiate the restoration of a clear water state in shallow eutrophic lakes.
改性土壤絮凝的地球工程方法已广泛应用于减轻相对较小湖泊的藻类水华和富营养化。然而，鉴于这些水体在人类健康和福利方面的多种功能，在将其应用于大型天然湖泊之前，应该对其生态风险和可行性进行检查和识别。2010 年和 2011 年夏季，在太湖进行了原位中观实验，以研究改性土壤絮凝。壳聚糖改性高岭土（CMK）土壤用于絮凝藻类水华并提高水的透明度，以促进浅水富营养化湖泊中的沉水植物苦草的重建。此外，还评估了 CMK 土壤的生态效应。结果表明，重复添加 CMK（每次 0.3g/L）可改善水质，包括 Chl-a、TN 和 TP 浓度；TN/TP 比；浊度；氧化还原条件；以及硝化和反硝化活性。这些效果持续了 48 天。在第四次添加 CMK 后，除隐藻外，所有浮游植物类别的生物量减少了>90%（约 1-2×10 个细胞/L 或 0.38-0.55mg/L 的湿重）。第一次添加 CMK 后，浮游动物生物量明显减少，桡足类动物成为优势种。然而，这些效果并没有持续很长时间。最重要的是，通过重复的 CMK 絮凝改善水的透明度和水质，成功恢复了沉水植物苦草。然而，碳水化合物耗尽和游离氨基酸积累的指标表明植物经历了生理压力。苦草的重新建立加强了重复 CMK 给药对水质的积极影响，并促进了清水状态。鉴于其易于移植、高抗逆性和生理特性，建议在浅水富营养化湖泊中进行苦草的营养繁殖，可将其作为絮凝后效果的指标。总之，重复添加 CMK 和苦草的植被恢复相结合，可以有效地改善水质，启动浅水富营养化湖泊的清水状态恢复。
