Abstract Liquid-phase nonpoint source pollution dispersion and removal on sustainable urban drainage systems (SUDS) is an important issue for urban pollution mitigation which remains a challenge, as current researches mostly focus on pollutants removal by settling. Nevertheless, most of liquid-phase pollutants behave as dissolved substances on overland flow and, therefore, they cannot be trapped, but uptake by biological mechanisms and adsorbed by green infrastructure media. Hence, dispersion of dissolved pollutant is of great importance for liquid-phase pollution removal, as it also increases contact with underlying media in the SUDS. This paper addresses the liquid-phase pollutant dispersion on conveyance structures within different materials, using experimental and modelling analysis. Hydrodynamic dispersion and flow velocity were analysed separately, or conjoint, using dispersivity, as it is a key factor for porous solute transport and removal. Therefore, the effect of different covers on pavements draining to, or as part of, SUDS with very shallow runoff was investigated. Four scenarios were performed in triplicate to measure the flow velocity and the conservative solute transport across longitudinal section of flume (experimental indoors self-contained setup) using electrolyte tracer under different flow discharges (32–1813 ml s−1) with 0.8, 4.4 and 13.2% slopes. For one scenario, free water flow on a smooth surface was performed and results were used as control. For the three remaining scenarios: sand roughness, stone and synthetic grass covers were investigated. The ratio of the dispersion coefficient and flow velocity (i.e. dispersivity factor) was also determined and compared with control. Finally, data were analysed considering flow regimes, using the dimensionless Reynolds and Froude numbers. Results showed that surface covers caused reduction in the flow velocity, from 1.2 to 7.7 fold. However, dispersivity factor can be increased from 3 to nearly 10 orders of magnitude for the three scenarios, compared to control, due to the dual effect on hydrodynamic dispersion coefficient and flow velocity. Results here presented should be helpful to better understand dissolved non-point source pollution dispersion and how different land covers can effect pollutant removal.

中文翻译：

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液相非点源污染通过输送结构分散到不同土地覆盖范围内的可持续城市排水系统

摘要 可持续城市排水系统（SUDS）的液相非点源污染分散和去除是城市污染缓解的一个重要问题，仍然是一个挑战，目前的研究主要集中在通过沉降去除污染物。然而，大多数液相污染物在地表流中表现为溶解物质，因此它们不能被捕获，而是被生物机制吸收并被绿色基础设施介质吸附。因此，溶解污染物的分散对于液相污染去除非常重要，因为它也增加了与 SUDS 中底层介质的接触。本文使用实验和建模分析解决了液相污染物在不同材料内的输送结构上的扩散问题。使用分散性单独或联合分析流体动力学分散和流速，因为它是多孔溶质传输和去除的关键因素。因此，研究了不同覆盖物对排放到具有非常浅径流的 SUDS 或作为其一部分的路面的影响。四个场景一式三份地进行，以使用电解质示踪剂在不同流量排放（32-1813 ml s-1）下测量流速和穿过水槽纵向截面的保守溶质传输（实验性室内独立设置），分别为 0.8、4.4 和13.2% 的斜率。对于一种情况，在光滑表面上进行自由水流并将结果用作对照。对于剩下的三个场景：沙子粗糙度、石头和合成草覆盖物进行了调查。弥散系数与流速的比值 (i. e. 分散系数）也被确定并与对照进行比较。最后，使用无量纲雷诺数和弗劳德数分析考虑流态的数据。结果表明，表面覆盖导致流速降低，从 1.2 到 7.7 倍。然而，由于对流体动力扩散系数和流速的双重影响，与控制相比，三种情况下的扩散系数可以从 3 个数量级增加到近 10 个数量级。这里呈现的结果应该有助于更好地理解溶解的非点源污染扩散以及不同的土地覆盖如何影响污染物的去除。结果表明，表面覆盖导致流速降低，从 1.2 到 7.7 倍。然而，由于对流体动力扩散系数和流速的双重影响，与控制相比，三种情况下的扩散系数可以从 3 个数量级增加到近 10 个数量级。这里呈现的结果应该有助于更好地理解溶解的非点源污染扩散以及不同的土地覆盖如何影响污染物的去除。结果表明，表面覆盖导致流速降低，从 1.2 到 7.7 倍。然而，由于对流体动力扩散系数和流速的双重影响，与控制相比，三种情况下的扩散系数可以从 3 个数量级增加到近 10 个数量级。这里呈现的结果应该有助于更好地理解溶解的非点源污染扩散以及不同的土地覆盖如何影响污染物的去除。