Characterization and sources of aromatic hydrocarbons (BTEX) in an urban site of Tijuana, Baja California, Mexico

Benzene, toluene, ethylbenzene, p-xylene, O3, NOx, CO, PM2.5and meteorological parameters were measured in urban air of one site in Tijuana, Baja California, Mexico during winter 2016-2017. Samples were collected using 1.5 h time intervals at four different sampling periods (B1: 07:30-09:00 h, B2: 12:00-13:30 h, B3: 15:00-16:30 h, B4: 18:00-19:30 h) before being analyzed by gas chromatography with flame ionization detection. The highest concentrations of BTEX occurred during the morning (B1) and afternoon (B4) sampling periods. Mean concentrations of BTEX were 32.40 μg/m3for benzene; 13.28 μg/m3for toluene; 17.16 μg/m3for p-xylene; and 7.02 μg/m3for ethylbenzene. The toluene/benzene, xylene/ethylbenzene concentration ratios and meteorological analysis indicated that BTEX levels were influenced by local and fresh emissions (vehicular traffic). Bivariate (Pearson correlation) and multivariate analyses (Principal Component Analysis) were performed in order to correlate BTEX concentrations with criteria air pollutants and meteorological parameters to infer their possible sources. These results suggest that changes in the existing environmental policies should therefore be applied to improve air quality