Mathematical relationships for metal build-up on urban road surfaces based on traffic and land use characteristics

• Sources of metal build-up: Mn-geogenic; Pb, Cu, Zn, Cr, Ni and Cd-traffic related.
• Traffic sources: vehicle wear-Pb, Cu, Zn; exhaust-Cr, Ni; exhaust and wear-Cd.
• Land use does not exhibit clear pattern in influencing metal build-up process.
• Reliable prediction equation developed for cumulative fuel related metal load.
• Prediction equation for wear-related metal load is suitable for preliminary studies.

The study investigated the influence of traffic and land use parameters on metal build-up on urban road surfaces. Mathematical relationships were developed to predict metals originating from fuel combustion and vehicle wear. The analysis undertaken found that nickel and chromium originate from exhaust emissions, lead, copper and zinc from vehicle wear, cadmium from both exhaust and wear and manganese from geogenic sources. Land use does not demonstrate a clear pattern in relation to the metal build-up process, though its inherent characteristics such as traffic activities exert influence. The equation derived for fuel related metal load has high cross-validated coefficient of determination (Q2) and low Standard Error of Cross-Validation (SECV) values which indicates that the model is reliable, while the equation derived for wear-related metal load has low Q2 and high SECV values suggesting its use only in preliminary investigations. Relative Prediction Error values for both equations are considered to be well within the error limits for a complex system such as an urban road surface. These equations will be beneficial for developing reliable stormwater treatment strategies in urban areas which specifically focus on mitigation of metal pollution.