Diffusive monitoring of C₆—C₉hydrocarbons in urban air in Sweden

Abstract

A method for diffusive monitoring of C6–C9 hydrocarbons was evaluated. This technique, based on passive sampling of urban air during a 7 d period followed by analysis via thermal desorption and gas chromatography with a flame ionization detector, has been used to monitor urban air quality in a network of Swedish municipalities during the winter months (October–March) since October 1992. Detection limits, precision, bias, sources of error and sample stability during storage are presented. Parallel measurements made using a different method (on-site gas chromatography) confirm the validity of this method. Mean concentrations of benzene in 30 Swedish cites for the sampling season October 1994–March 1995 range from 2.4 to 6.2 µg m–3. Average benzene concentrations, measured over a 3 year period in 12 Swedish municipalities, have been steadily decreasing, in some cases by 50% or more.