Diffusive monitoring of C6—C9 hydrocarbons 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.