Skip to main content
main-content

Über dieses Buch

This book discusses the physicochemical changes (transformations) that metals deposited on urban road surfaces undergo during dry weather periods, in order to provide insights into their potential impacts on stormwater quality. Based on extensive field experiments, and laboratory and data analyses, it examines transformation characteristics of metals with respect to the particle size of road dust, antecedent dry days and land uses. Further, it proposes a new risk-assessment methodology, improving the original human health-risk indices based on the transformation characteristics and potential bioavailability of metals in order to evaluate the risks posed by metals in stormwater. This book is of interest to researchers and decision-makers developing appropriate pollution mitigation measures to enhance the quality of stormwater, targeting the effective reuse of stormwater in urban areas.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Metals in the Urban Stormwater Environment

Abstract
Stormwater reuse is one of the viable alternatives to overcome the growing water demand in urban areas. However, effective use of stormwater as an alternative water resource is constrained due to the presence of toxic pollutants generated by natural and anthropogenic processes. Stormwater quality is further impacted by the behavioural changes to pollutants, resulting from the transformation of their physical and chemical characteristics. The transformed pollutants can have different persistence, toxicity, mobility and bioavailability characteristics compared to their original form. Therefore, improving stormwater quality by understanding the behavioural changes of pollutants and quantification of the associated risks of transformed pollutants is essential to ensure the safe use of stormwater. This chapter discusses the potential transformation characteristics of metals associated with road dust, which is among the major toxic pollutants found in urban areas, and the factors influencing metal transformations and resulting stormwater quality impacts.
Ayomi Jayarathne, Buddhi Wijesiri, Prasanna Egodawatta, Godwin A Ayoko, Ashantha Goonetilleke

Chapter 2. Research Design for Investigating Metal Transformations on Urban Roads

Abstract
Investigations into the transformation characteristics of metals deposited on urban roads required a scientifically robust research design. Sample collection and laboratory analyses were two important steps in the overall research design. This chapter provides a detailed discussion on the methods adopted for road dust sample collection, sample handling and preservation, and laboratory experiments for the analysis of selected metals and key physicochemical parameters of road dust.
Ayomi Jayarathne, Buddhi Wijesiri, Prasanna Egodawatta, Godwin A Ayoko, Ashantha Goonetilleke

Chapter 3. Metal Transformation and Stormwater Quality

Abstract
A detailed understanding of the metal transformation processes and consequent stormwater quality impacts provides a platform for the implementation of effective stormwater pollution mitigation strategies. This chapter discusses the geochemical behaviour of common metals associated with road dust and the processes they undergo during dry weather periods, in order to understand their mobility characteristics and potential stormwater quality impacts. Among the analysed metals, Zn and Cd have the greatest affinity for the readily available exchangeable geochemical fraction, whilst Cu and Pb are likely to associate with the reducible and oxidisable geochemical fractions. The characteristic affinity of Ni and Cr for the residual geochemical fraction indicates their low mobility. With increasing residence time, weakly bound metals gradually transform into more stable chemical forms. The transformation rate of metals follow the order: Pb > Cu > Zn > Cd, which is inversely opposite to the order of their mobility. Based on the transformation rate and mobility order, metals such as Cd and Zn can adversely influence stormwater quality due to their readily available nature.
Ayomi Jayarathne, Buddhi Wijesiri, Prasanna Egodawatta, Godwin A Ayoko, Ashantha Goonetilleke

Chapter 4. Assessment of Human Health Risks from Metals in Urban Stormwater Based on Geochemical Fractionation and Bioavailability

Abstract
Risks posed by metals in stormwater is directly influenced by their geochemical fractionation and, in turn, the bioavailability. Therefore, accurate quantification of the risks from metals should be undertaken by considering these two key aspects. This chapter presents a novel approach to quantify the human health risks of metals, among the common stormwater pollutants found in urban areas, considering their geochemical fractionation and bioavailability characteristics. Stormwater quality and quantity modelling approaches were used to convert metal build-up loads to corresponding metal concentrations in stormwater. The results of the modified risk assessment discussed in this chapter highlights the drawbacks in using classical health risk indices and the importance of upgrading the risk assessment methods to avoid the over-estimation of risk posed by metals. Based on the modified hazard index, there is a low or no health risk from metals in stormwater runoff originating from the urban land uses investigated in this study.
Ayomi Jayarathne, Buddhi Wijesiri, Prasanna Egodawatta, Godwin A Ayoko, Ashantha Goonetilleke

Chapter 5. Practical Implications and Recommendation for Future Research

Abstract
This chapter summarises the key outcomes of the research study undertaken to investigate metal transformations on urban road surfaces and their potential impacts on stormwater quality. In particular, it discusses the practical implications of the research outcomes in relation to stormwater pollution mitigation in the context of stormwater reuse. Stormwater pollution mitigation strategies should be implemented such that they specifically address the impacts of fine road dust particles and more mobile metals such as Zn and Cd in stormwater runoff. Furthermore, it is important to enhance current risk assessment methods by taking into consideration the geochemical behaviour of metals for accurate risk quantification. The chapter further discusses the current knowledge gaps where further research is needed. These include, the investigation of transformation processes of other toxic pollutants and the influence of additional factors on metal transformation, and the need for integrating factors influencing metal transformation into stormwater quality models for developing effective stormwater pollution mitigation strategies.
Ayomi Jayarathne, Buddhi Wijesiri, Prasanna Egodawatta, Godwin A Ayoko, Ashantha Goonetilleke

Backmatter

Weitere Informationen