A two-year monitoring program of aromatic hydrocarbons in Rio de Janeiro downtown area

Benzene, toluene, ethylbenzene, m+p+o-xylene (BTEX) and two trimethylbenzenes (BTEXT) were monitored in Rio de Janeiro downtown area during 2004 and 2005. Some criteria pollutants and meteorological parameters were also determined in order to assess the main data correlations. 94 samples were collected, using activated charcoal cartridges, between 9:00 am and 3:00 pm. The mean concentrations obtained were: 14.5, 22.8, 9.19, 19.3, 8.5, 10.4 and 12.1 pg m(-3) for benzene, toluene, ethylbenzene, m+p-xylene, o-xylene, 1,2,3-trimethylbenzene and 1,3,5-trimethylbenzene, respectively. These values are similar to mean concentrations obtained in the Brazilian cities of Porto Alegre, Volta Redonda and Sao Paulo, which use the same type of fuel. Multivariate analyses showed that individual BTEXT are emitted by the same source and are not well correlated with other primary pollutants. These results may be due to the contribution of evaporative losses of the BTEXT and to the formation of secondary volatile organic compounds in the atmosphere.