Evaluation of metal loadings and bioavailability in air, water and soil along two highways of British Columbia, Canada

A comprehensive multi-media monitoring field investigation, which included: atmospheric, storm-water runoff, road sediment and soil samples, was carried out at two highway sites in Vancouver, Canada, focused on Cu, Fe, Pb, Mn, and Zn, due to their prevalence in most highway environments, both locally and worldwide. Metal potential bioavailability was evaluated through sequential extraction in the case of particulates and via exchange with a chelating resin for highway runoff. Road sediment showed in most cases a close resemblance with runoff and atmospheric metal concentrations (Fe > Zn > Mn > Cu > Pb), suggesting that road sediment is a useful indicator of current metal loadings and a key factor influencing the quality of urban watersheds. Metals showed increasing bioavailability with decreasing particle size in all samples. Thus, bioavailability was low in roaddust and roadside soils, intermediate in dustfall, and highest in atmospheric suspended particulates and runoff. Speciation analyses in different environmental media suggested that Zn is a metal of future potential concern. Zinc was second in concentration to Fe in most dust, air and water samples, and exhibited the highest mobility and potential bioavailability.