Intercomparison between gas-chromatography and long-path UV DOAS techniques for the measurement of benzene and toluene in urban atmospheres

摘要

Abstract: An intercomparison between DOAS and gas-chromatographic techniques for the measurement of the concentration of benzene and toluene in the air has been carried out in Milan, Italy during the winter of 1994. Measurements of the natural radioactivity due to Radon have been carried out for a direct description of the mixing properties of the atmosphere. The temporal trend of primary pollutants, including hydrocarbons, follow, as expected, that of radioactivity. The results show that large discrepancies between the two methods have to be associated with the stratification of the atmosphere caused by ground based inversions. Scatter plots of GC against DOAS data show acceptable agreements, while the nature of observed offsets in DOAS system need further investigation. The results also show that the measurements are self consistent as they fit the physio-chemical evolution of atmospheric pollution at the site of sampling. In addition, data obtained from DOAS may be used to describe the evaluation of vertical mixing through the ratio toluene/benzene. Data on this new and important aspect are also presented. !0