Influence of Traffic and Land Use on Urban Stormwater Quality

Urbanisation introduces a range of pollutants to the urban environment. These pollutants include many toxic species. They are primarily sourced from traffic and land use related activities. The pollutants are directly deposited on ground surfaces or initially emitted to the atmosphere and subsequently deposited on ground surfaces via depositional processes. These pollutants are removed by stormwater runoff and transported to receiving water bodies, undermining the urban water environment. This chapter discusses the primary traffic related pollutants and their transport pathways. Pollutants discussed include solids, heavy metals, polycyclic aromatic hydrocarbons and airborne particulate pollutants while their transport pathways include atmospheric build-up, dry and wet deposition, build-up and wash-off on road surfaces.

Investigations into pollutant processes of atmospheric build-up, dry and wet deposition and build-up on urban surfaces require a scientifically robust research program. This chapter primarily discusses strategies adopted for study sites selection, the field sampling program and laboratory testing. Discussion of the sampling program includes sample collection methods for atmospheric pollutant build-up, atmospheric deposition and build-up on road surfaces.

This chapter discusses the influence of traffic and land use factors on atmospheric pollutants build-up, dry and wet deposition and build-up on urban surfaces. Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) were the focus of discussion in this chapter as these pollutants are ubiquitous in the urban environment, being commonly associated with traffic and anthropogenic activities common to urban areas and are toxic to human and ecosystem health. The research outcomes presented in this chapter confirm the influential role played by atmospheric pollution in stormwater pollution. The study outcomes also highlight the linkage between pollutants species with their potential sources and influential factors. Furthermore, the linkages between pollutants in the atmospheric phase, depositions and build-up on urban surfaces are also identified. For example, Zn was found to be the most abundant heavy metal element present in atmospheric build-up, atmospheric deposition and build-up on road surfaces, whilst light molecular weight PAHs have a higher concentration and spatial variability in both, atmospheric and road surface phases. The analysis also highlighted the influence exerted by heavy duty vehicle traffic on pollution in the urban environment, particularly in industrial land use areas. The knowledge created will contribute to informed decision making for minimising urban stormwater pollution and thereby safeguarding the urban water environment. In addition, these outcomes can also be applied in urban transport planning in order to enhance urban liveability.

Accurate stormwater quality prediction is essential for effective stormwater quality mitigation. The knowledge created in the previous chapters was applied for predicting stormwater quality using mathematical models. This chapter presents a detailed discussion of the outcomes of the modelling study including model selection, input parameter determination and model setup. The model setup procedure consisted of model schematisation, determination of boundary conditions and replication of pollutants build-up and wash-off processes. Eventually, the estimation results using the modelling approach developed are given and a series of predictive equations based on traffic and land use characteristics were developed. These outcomes are expected to contribute to the translation of research outcomes into practical recommendations for model developers, decision-makers and stormwater treatment system designers.

This chapter provides a consolidated summary of the outcomes from the research study undertaken to investigate the influence of traffic and land use on pollutant processes as well as the practical application of the study findings. The chapter also discusses key areas where currently, there are significant knowledge gaps and further investigations are warranted. These include, the assessment of ecological and human health risks posed by stormwater pollutants, the investigation of other traffic related pollutants and the understanding of the adsorption mechanisms of pollutants—solids inherent in the different transport pathways.