Untreated runoff quality from roof and road surfaces in a low intensity rainfall climate

Frances J Charters; Thomas A Cochrane; Aisling D O'Sullivan

doi:10.1016/j.scitotenv.2016.01.093

Untreated runoff quality from roof and road surfaces in a low intensity rainfall climate

Sci Total Environ. 2016 Apr 15:550:265-272. doi: 10.1016/j.scitotenv.2016.01.093. Epub 2016 Jan 25.

Authors

Frances J Charters¹, Thomas A Cochrane², Aisling D O'Sullivan³

Affiliations

¹ Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand. Electronic address: frances.charters@pg.canterbury.ac.nz.
² Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand. Electronic address: tom.cochrane@canterbury.ac.nz.
³ Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand. Electronic address: aisling.osullivan@canterbury.ac.nz.

PMID: 26820930
DOI: 10.1016/j.scitotenv.2016.01.093

Abstract

Sediment and heavy metals in stormwater runoff are key pollutants of urban waterways, and their presence in stormwater is driven by climatic factors such as rainfall intensity. This study describes the total suspended solids (TSS) and heavy metal concentrations found in runoff from four different urban surfaces within a residential/institutional catchment, in a climate where rainfall is typically of low intensity (<5.1mm·h(-1)). The results were compared to untreated runoff quality from a compilation of international studies. The road runoff had the highest TSS concentrations, while copper and galvanized roof runoff had the highest copper and zinc concentrations, respectively. Pollutant concentrations were found to be significantly different between surfaces; quantification and prediction of pollutant contributions from urban surfaces should thus take account of the different surface materials, instead of being aggregated into more generalized categories such as land use. The TSS and heavy metal concentrations were found to be at the low to medium end of ranges observed internationally, except for total copper and zinc concentrations generated by dissolution of copper and galvanized roofing material respectively; these concentrations were at least as high as those reported internationally. TSS wash-off from the roofs was seen to be a source-limited process, where all available TSS is washed off during the rain event despite the low intensity rainfall, whereas both road TSS and heavy metals wash-off from roof and road surfaces appeared to all be transport-limited and therefore some carryover of pollutants occurs between rain events. A first flush effect was seen from most surfaces for TSS, but not for heavy metals. This study demonstrates that in low intensity rainfall climates, quantification of untreated runoff quality from key individual surface types in a catchment are needed to enable development of targeted and appropriately sized stormwater treatment systems.

Keywords: Heavy metals; Metals partitioning; Road runoff; Roof runoff; Total suspended solids.

Publication types

Research Support, Non-U.S. Gov't