Application of diffusion-based surveys in the district-wide assessment of benzene and select volatile organic compounds in urban environments: a case study from Renfrewshire, Scotland

Benzene (with toluene, ethyl benzene and xylene isomers) concentrations were measured at nine locations in Renfrewshire district between February 1996 and July 1998. Samples were collected by both active and diffusion-based sampling and the compounds were quantified by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The study highlighted the ability of diffusion sampling to provide an effective district-wide assessment of volatile organic compounds (VOCs) in urban environmental assessment. Vehicle movement was confirmed as the dominant influence on benzene and associated VOCs in the atmosphere, with strong variations in monthly average concentrations across the study area. For benzene, peak monthly averages were observed on the order of 5-6 ppb v/v, with minimum values of <<0.5 ppb v/v. The impact of a major traffic intervention on benzene levels was followed. and was found to influence atmospheric concentrations over a wide geographical area. An evaluation of the relationship between VOCs and meteorological parameters identified the impact of photo-oxidation and air mass mixing on average atmospheric concentrations.