C1 to C9 volatile organic compound measurements in urban air

Urban atmospheric samples were collected in A Corun˜a (NW Spain) and analysed for volatile organic compounds. One hundred and twenty one hour samples were collected in winter 2000. The ambient air was rich in benzene, toluene, ethylbenzene and xylenes (BTEX) and especially toluene (mean: 23.6 Ag m 3, median: 14.66 Ag m 3), but the presence of chlorinated compounds was also notable. High concentrations of 1,4-dichlorobenzene (mean: 11.4 Ag m 3, max: 90.4 Ag m 3) were recorded. Multivariate analysis of VOC, trace gases (NOx, NO2, NO, SO2 and O3) and meteorological variables (temperature, wind direction and speed, precipitation and radiation) was applied and correlations between VOC were also studied. Principal component analysis and correlation analysis confirm traffic as the main source of VOC in the area, although the importance of evaporative sources is also reflected. Three groups of samples were obtained by cluster analysis; these groups are formed depending on the content of aromatics and ozone and, in many cases, on the sampling hour.