Understanding heavy metal and suspended solids relationships in urban stormwater using simulated rainfall

Abstract

Urban stormwater from simulated rainfall on three different landuses in Queensland State, Australia (residential, industrial, commercial) was analysed for heavy metals and physico-chemical parameters such as Dissolved Organic Carbon (DOC) and Total Suspended Solids (TSS). Rainfall events were simulated using a specially designed rainfall simulator for paved surfaces. Event mean concentration samples were separated into five different particle sizes and analysed individually for eight metal elements (Zn, Fe, Cr, Cd, Cu, Al, Mn and Pb). Multivariate data analysis was carried out for the data thus generated. It was found that DOC and TSS influence the distribution of the metals in the different particle size classes. Zn was correlated with DOC at all three sites. Similarly, Pb, Fe and Al were correlated with TSS at all sites. The distribution of Cu was found to vary between the three sites, whilst Cd concentrations were too low to assess any relationships with other parameters. No correlation between Electrical Conductivity (EC), pH and heavy metals was found at the three sites. The identification of physico-chemical parameters influencing the distribution process kinetics of heavy metals in urban stormwater will significantly enhance the efficiency of urban stormwater management systems.

Index models to evaluate the potential metal pollution contribution from washoff of road-deposited sediment

“…A key point is that the transport factor used in the RDS index was mainly derived from RDS washoff experiments using a rainfall simulator, and the impacts of differences between simulated rainfall and natural rainfall values on the accuracy of the transport factors are still unclear (Herngren et al, 2005;Zhao et al, 2010;Brodie and Egodawatta, 2011). The use of simulated rainfall could provide greater flexibility and control of the fundamental rainfall parameters such as intensity and duration and thereby helped to eliminate some of the variables which inherently increase the complexity of stormwater quality research.…”

“…Large amounts of pollutants, such as nutrients, metals, and hydrocarbons, are usually transported in RDS washoff (Sartor and Boyd, 1972;Huber and Dickinson, 1988;Al-Khashman, 2007). Quantifying the relationship between RDS and washoff particles in urban runoff could provide a new method for estimating the pollution load that a waterway receives (Herngren et al, 2005;Zhao et al, 2011). A range of diffuse pollution models for urban areas have been proposed, including STORM, HSPF, DR3M-QUAL, SWMM, and SLAMM, and they have been used to estimate pollutant loads in runoff (Egodawatta et al, 2007;Wang et al, 2011).…”

Understanding the relationship between heavy metals in road-deposited sediments and washoff particles in urban stormwater using simulated rainfall

“…5). Although rainfall intensity and duration affected the amount of RDS and their associated metals in washoff water [5,6], solid phase concentrations of heavy metal in washoff particles did not vary throughout the entire washoff process. Clearly, our findings should contribute to quantification of the relationship between heavy metal pollutants in RDS and washoff particles.…”

“…The rainfall simulation was designed according to Herngren et al (2005), Egodawatta et al (2007), and Xie et al (2008) [5,7,25]. The device consisted of two rainfall simulators.…”

“…Heavy metals washoff from RDS is an increasing problem associated with rapid urbanization that results in urban diffuse pollution [3,4]. Because of the difficulty associated with using natural rainfall events to investigate rigorous RDS washoff processes [5,6], washoff is the least understood among the three processes that occur before materials enter receiving waters (RDS buildup, washoff and transport) [7]. An in-depth understanding of these processes is essential to elucidation of the relationships of pollution between RDS and washoff particles [8,9].…”