DIFFUSIVE MONITORING OF C-6-C-9 HYDROCARBONS IN URBAN AIR IN SWEDEN

A method for diffusive monitoring of C-6-C-9 hydrocarbons was evaluate d. This technique, based on passive sampling of urban air during a 7 d period followed by analysis via thermal desorption and gas chromatogr aphy with a flame ionization detector, has been used to monitor urban air quality in a network of Swedish municipalities during the winter m onths (October-March) since October 1992. Detection limits, precision, bias, sources of error and sample stability during storage are presen ted. Parallel measurements made using a different method (on-site gas chromatography) confirm the validity of this method. Mean concentratio ns of benzene in 30 Swedish cites for the sampling seas on October 199 4-March 1995 range from 2.4 to 6.2 mu g m(-3). Average benzene concent rations, measured over a 3 year period in 12 Swedish municipalities, h ave been steadily decreasing, in some cases by 50% or more.