Variability and uncertainty of particle build-up on urban road surfaces

Particle build-up is a key stormwater pollutant process that is typically replicated using a power function with increasing antecedent dry days. Though the use of a power function is recommended by a range of researchers, its applicability is demonstrated primarily for residential roads. Particle build-up process is also subjected to significant variability due to catchment heterogeneity and variability associated with source characteristics such as traffic and land use. Variability in the build-up process and use of stereotypical coefficients can lead to significant model uncertainty. This study evaluates particle build-up characteristics on urban road surfaces using an extensive field investigation program, giving specific priority to industrial and commercial roads. Based on the outcomes, particle build-up process characteristics and respective uncertainties were evaluated and compared for road surfaces in residential, industrial and commercial areas. The study primarily found that both, industrial and commercial land uses generally manifested greater particle build-up loads compared to residential land uses. The study provides estimates for build-up coefficients for a range of land uses, including industrial and commercial with their potential uncertainties in build-up predictions. This provides new knowledge to improve stormwater quality modelling. Aside from land use, the proximity of sites to major road networks was also identified as a critical factor influencing the variability and uncertainty in particle build-up. Variability of the fraction of particles in the <75 μm size range with antecedent dry days exerts the most distinct influence on particle build-up variability across all land uses. The outcomes of this research study are expected to enhance stormwater quality monitoring, modelling and remediation, and thereby promoting greater protection of human and aquatic ecosystem health.