A study of trace metals and polycyclic aromatic hydrocarbons in the roadside environment

A study has been conducted of the concentrations of a range of inorganic elements and polycyclic aromatic hydrocarbons during a winter period at a roadside location in Birmingham, UK. Particle number and NOx concentrations were also determined continuously during the study. The analysis of size distributions of trace metals and the calculation of enrichment factors allows the identification of a number of elements which appear to be related with anthropogenic emissions. Using NOx and particle count as tracers of road traffic emissions, the elements Cu, Zn, Mo, Ba and Pb show significant correlations indicative of a traffic source contribution. When the results for the PM0.2 size fraction are compared with those for PM 10, correlations with NOx and particle count improve for Ba and to a lesser degree for Pb, indicating association with very fine particles, whereas for Cu and Mo, the correlations are weaker for the smaller size fraction. Correlations between methylphenanthrenes, often used as tracers of diesel exhaust, particle count and NOx are significant, while correlations between methylphenanthrenes and calcium become increasingly strong moving from PM10 through to PM0.2, suggesting an exhaust emission of this element. Enrichment factors for lead and its correlation with NOx remain elevated despite the cessation of use of lead in automotive gasoline in the UK, and a large reduction in lead in air concentrations. The data are supportive of the conclusion that the enrichment of most trace elements in roadside aerosol derives from vehicle wear products rather than exhaust emissions, for which organic compounds are likely to prove better source tracers. (C) 2003 Elsevier Science Ltd. All rights reserved.