An Innovative Method for Spatial Quantification of Contaminant Buildup and Wash-off from Impermeable Urban Surfaces

A method was developed that employs thin boards (0.56 m) comprising different paving materials (2 asphalt types and concrete) typically used in urban environments. Boards can be placed at various locations of interest within an urban catchment to investigate accumulation of contaminants over specified periods of time. Boards are then placed under a rainfall simulator in order to generate runoff under controlled conditions. We successfully applied this method to investigate contaminant build-up at a University carpark, showing accumulation mainly occurred within the first 6 days. Resulting wash-off curves were used to determine coefficients for build-up and wash-off functions (maximum build-up, half-saturation time and wash-off coefficient) that can be applied to model the fate of contaminants in stormwater models (e.g. SWMM). Results also showed that concentrations of total suspended solids (TSS) are linearly correlated with total metal concentrations.