Rainfall Runoff and Dissolved Pollutant Transport Processes Over Idealized Urban Catchments

Taotao Zhang,Dongfang Liang,Hongwu Tang,Yang Xiao,Bin Luan,Saiyu Yuan

doi:10.3389/feart.2020.00305

Abstract

Urban stormwater runoff is often considered as one of the most significant contributors to water pollution. Particulates are commonly regarded as the primary form of pollutant transport in the urban environment, but the contribution from the dissolved pollutants can also be significant. This study aims to investigate the dissolved pollutant transport process over urban catchments, especially the effects of buildings and spatial distribution of pollutants. The concept of “exchange layer” has been adopted and an equation has been proposed to describe the release process of dissolved pollutant from the exchange layer to the runoff water. A horizontal two-dimensional water flow and pollutant transport model has been developed for predicting dissolved pollutant runoff based on the shallow water assumptions and the advection-diffusion equation. A series of laboratory experiments have been conducted to verify the proposed model. It has been demonstrated that both the rainfall runoff and the pollutant runoff can be predicted accurately. Buildings slow down the runoff and pollutant transport processes, especially when buildings are staggered. The non-uniform distribution of pollutants over the catchment greatly influences the pollutant transport process over the catchment. This work provides insight into the effects of buildings and initial pollutant distribution on the dissolved pollutant transport phenomenon, which can help better design the pollution mitigation strategies.

Highlights

Urban stormwater runoff has been widely recognized as an important source for water quality degradation (Brezonik and Stadelmann, 2002; Shaw et al, 2006; Brett and Gavin, 2010; Revitt et al, 2014)
Many researchers have focused on the pollutant transport over simple impervious surfaces, such as road and roof surfaces (Metcalf and Eddy Inc, 1971; Sartor et al, 1974; Kim et al, 2005; Egodawatta et al, 2007, 2009; Muthusamy et al, 2018), and have established and improved the first-order decay model
An accurate pollutant transport model can accurately predict the pollutant transport process, which is crucial for the design of pollution mitigation strategies such as rainwater collection and treatment plants

Summary

Introduction

Urban stormwater runoff has been widely recognized as an important source for water quality degradation (Brezonik and Stadelmann, 2002; Shaw et al, 2006; Brett and Gavin, 2010; Revitt et al, 2014). Ongoing urbanization and the increased urban ground area are likely to exacerbate the problem (Wang et al, 2013; Naves et al, 2017) In this context, an appropriate pollutant transport model for predicting the runoff processes over contaminated grounds will be valuable for understanding the urban pollutant transport process and mitigating water pollution. Metcalf and Eddy Inc (1971) proposed the exponential wash-off equation, which assumes that the rate of pollutant transport from an impervious surface is directly. Current urban water quality models are generally based on the above exponential equation (e.g., SWMM, STORM, etc.). This simple exponential relationship neglect spatial heterogeneity of the catchment. An accurate pollutant transport model can accurately predict the pollutant transport process, which is crucial for the design of pollution mitigation strategies such as rainwater collection and treatment plants

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