Yu Congrong, Ye Xiuhui, Li Ying, Huang Ching-Sheng, Yu Zhongbo, Chen Gang, Hao Xiaoxiao
Hohai University, College of Hydrology and Water Resources, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing, Jiangsu 210098, China.
Hohai University, College of Hydrology and Water Resources, State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing, Jiangsu 210098, China.
Sci Total Environ. 2023 Sep 20;892:164427. doi: 10.1016/j.scitotenv.2023.164427. Epub 2023 May 26.
The capture of colloidal fine suspended particles by vegetation plays an important role in water quality of the shallow aquatic system under rainfall. Quantifying impact of rainfall intensity and vegetation condition on this process remains poorly characterized. In this study, the colloidal particle capture rates under three rainfall intensities, four vegetation densities and with submerged or emergent vegetation were investigated in different travel distance in a laboratory flume. Considering vegetation as porous media, non-Darcy's law with rainfall as a source term, was coupled with colloid first-order deposition model, to simulate the particle concentration changes with time, determining the particle deposition rate coefficient (k), representing capture rate. We found that the k increased linearly with rainfall intensity; but increased and then decreased with vegetation density, suggesting the existence of optimum vegetation density. The k of submerged vegetation is slightly higher than emergent vegetation. The single collector efficiency (η) showed the same trend as k, suggesting colloid filtration theory well explained the impact of rainfall intensity and vegetation condition. Flow hydrodynamic enhanced the k trend, e.g., the theoretical strongest flow eddy structure represented in the optimum vegetation density. This study is helpful for the design of wetland under rainfall, to remove colloidal suspended particles and the hazardous material, for the protection of the downstream water quality.
降雨条件下，植被对胶体细悬浮颗粒的捕获在浅水水生系统水质中起着重要作用。降雨强度和植被状况对该过程的影响量化仍缺乏充分的特征描述。本研究在实验室水槽中，研究了三种降雨强度、四种植被密度以及沉水或挺水植被条件下，不同行进距离的胶体颗粒捕获率。将植被视为多孔介质，以降雨为源项的非达西定律与胶体一级沉积模型相结合，模拟颗粒浓度随时间的变化，确定颗粒沉积速率系数（k），以代表捕获率。我们发现，k随降雨强度呈线性增加；但随植被密度先增加后降低，表明存在最佳植被密度。沉水植被的k略高于挺水植被。单收集器效率（η）与k呈现相同趋势，表明胶体过滤理论很好地解释了降雨强度和植被状况的影响。流动水动力增强了k的趋势，例如，理论上最强的流动涡结构出现在最佳植被密度时。本研究有助于设计降雨条件下的湿地，以去除胶体悬浮颗粒和有害物质，保护下游水质。
