Contaminant build-up on urban surfaces - where, when, and how much?
Stormwater from urban catchments in Christchurch contains considerable amounts of
contaminants such as heavy metals and various suspended solids that impact our urban
waterways. The three most common metal contaminants impacting urban waterways in
Christchurch and around New Zealand are zinc, copper, and lead. Heavy metal
concentrations measured during storm events in local waterways were found to be
consistently higher than recommended 80% ANZECC (2000) guidelines for the protection of
aquatic species. Sources of heavy metal contaminants have been identified from car traffic in
parking lots/roads and metal roofs.
In order to reduce the contaminant loading to our streams and implement best management
practices, a better understanding and quantification of contaminant sources (car parks / roads
/ roofs / etc), build-up, and wash-off is needed.
This project will investigate the relationships between contaminant build-up, surface
characteristics, rain characteristics and urban land use. It involves running a unique
experimental setup that uses thin boards made out of different materials (concrete, different
asphalt types) to capture and quantify contaminant build-up and wash-off. The project
involves setting the boards at different locations around campus (car parks, streets with high
traffic, low traffic, etc.) for a specific amount of time and then using a laboratory based
rainfall simulator to collect contaminants from the boards. Relationships between simulated
rainfall intensity and contaminant wash-off will also be investigated. All samples will be
analysed for TSS and Cu, Zn, and Pb (using UoC’s new ICPMS equipment). Contaminant
build-up and wash-off curves will be calculated using results from these experiments. The
resulting data will be used to:
a) build a model to estimate the source and delivery of contaminants to urban waterways
under various storm event scenarios.
b) develop guidelines for determining the best times for taking stormwater and receiving
stream samples relative to storm events and exposure times.
This study follows on from projects undertaken by NRE students in 2009 and during the
summer - so the students will be able to carry on the investigations using a well-tested setup.