In situ gas chromatographic measurements of halocarbons in an urban environment

A GC-ECD system has been used to make continuous measurements of nine halocarbons in the urban environment of Bristol, England over the course of about one month. A GC-FID system was deployed in the same location which simultaneously monitored over 30 C2–C8 hydrocarbons. In this paper, the halocarbon time series is presented and compared with the hydrocarbon data set. The influence of local sources is investigated by comparing the fluctuations in halocarbon concentrations with local weather conditions. A complex time series is seen, with no species displaying any clear diurnal cycle. Additionally, large deviations from baseline levels are observed for many of the compounds at different times. Local small-scale industry and landfill sites are postulated as the source of many of these excursions. The geography of Bristol has been found to influence levels of pollution in the city as the surrounding hills trap emissions and prevent their quick dispersion.