Sources and transport pathways of common heavy metals to urban road surfaces

• Source of Mn and Pb to urban atmosphere and roads: roadside soil disturbed by wind.
• Sources of Cu, Cr and Zn to urban atmosphere and roads: traffic emissions.
• Atmospheric deposition is the major pathway for Cu and Zn to road build-up.
• Direct deposition is the major pathway for Cr, Mn and Pb to road build-up.
• Traffic variables have similar influence on heavy metal transport pathways to roads.

Heavy metals that are built-up on urban impervious surfaces such as roads are transported to urban water resources through stormwater runoff. Therefore, it is essential to understand the predominant pathways of heavy metals to the build-up on roads in order to develop suitable pollution mitigation strategies to protect the receiving water environment. The study presented in this paper investigated the sources and transport pathways of manganese, lead, copper, zinc and chromium, which are heavy metals commonly present in urban road build-up. It was found that manganese and lead are contributed to road build-up primarily by direct deposition due to the re-suspension of roadside soil by wind turbulence, while traffic is the predominant source of copper, zinc and chromium to the atmosphere and road build-up. Atmospheric deposition is also the major transport pathway for copper and zinc, and for chromium, direct deposition by traffic sources is the predominant pathway.