Published: May 2008 | Category: Environmental impacts of land transport , Research programme , Research & reports | Audience: General
In 2006–2007, 35 road-derived sediments (RDS) consisting of street sweepings and catchpit (ie sump) sediments, were collected from three cities in New Zealand; namely Auckland, Hamilton and Christchurch.
The concentrations, mobility and toxicity of contaminants were determined in order to assess the suitability of RDS for certain reuse applications.
The current situation in New Zealand is that all RDS must be disposed of in landfills. The RDS were analysed for total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs) and the heavy metals, lead, copper and zinc – with respective median (n=35) concentrations of 1220, 6.3, 122, 67, 422 μg/g.
Comparisons with soil guideline values for ecological protection (Dutch and Canadian) and reuse of biosolids for land application (New Zealand), indicated that zinc will be the most problematic contaminant with respect to mitigating environmental risks in any reuse applications of RDS in New Zealand.
Selected RDS freshwater leachates were toxic to the alga, Psuedokirchneriella subcapitata, at zinc concentrations of ca. 22-150 μg/L (EC50), however, leachate toxicity was reduced up to 225-fold when amended, or ‘stabilised’ with 10% compost.
Based on the results and potentially applicable guideline values, the reuse of RDS may be limited to applications that either physically (ie incorporation into concrete or asphalt) or chemically (ie addition of a ‘stabilising’ agents like compost or phosphate) immobilise problematic heavy metal contaminants, namely zinc.
Keywords: catch basins, catchpits, characterisation, cleanfill, contaminants, copper, debris, disposal, dust, heavy metals, landfill, leachate, leaching, lead, PAHs, particulates, petroleum, polycyclic aromatic hydrocarbons, recycling, reuse, road, runoff, sediment, sump, sweeping, toxicity, TPH, zinc
