In this work experiments were performed with vapor collection in columns to assess the evaporation profile of benzene from gasoline-ethanol blend fuels. The vapors from two columns simulating gasoline-contaminated soils (with and without ethanol) were monitored for 77 d. The instrumental analysis was performed by Gas Chromatography (GC) with a Flame Ionization Detector (FID). Compound identification was based on the GC retention times of standard BTX (benzene, toluene and xylenes). The concentration of benzene in the vapor phase decreased by 89.09%, considering the entire experimental period, while the toluene and xylene concentrations were increased by 239.34 and 251.78%, respectively. These results suggest that the benzene evaporation behavior was affected by the interactions among ethanol and other aromatic compounds. These results are particularly important, since ethanol is an alternative to gasoline blends. Furthermore, benzene (a well known carcinogen) was retained in the liquid phase and, in this way, can reach the underground water sources. These findings can point out necessary changes in traditional risk models for soil spills that are based on compound concentrations in the environment.
The main objective of present study was to assess the evaporation profile of monoaromatic compounds, namely, benzene, toluene, and xylenes (BTX) from gasoline-ethanol-blend fuels. The vapors from two river sand columns contaminated with gasoline and gasoline-ethanol were monitored for 77 d. Standards mixtures (batch tests) of benzene, toluene, and xylenes with different ethanol contents were also analyzed for evaporation rates studies. The instrumental analysis was performed via gas chromatography. The concentration of benzene in the vapor phase of the gasoline-ethanol column was decreased by 89.09%, considering the entire experimental period, whereas the toluene and xylenes concentrations were increased by 239.34 and 251.78%, respectively. In the batch tests, the benzene concentration in the vapor phase varied from 0.4 to 0.9 mg/L for ethanol concentrations (v/v) of 5 and 10%, respectively. For ethanol concentrations higher than 10%, no important changes in the benzene concentration were observed. The toluene exponentially increases between 20 and 30% ethanol concentration. and the maximum concentration of xylenes was observed when the ethanol concentration was 20% (v/v). These results suggest that the benzene evaporation behavior is preferentially affected by the interactions among ethanol and other aromatic compounds rather than the ethanol concentration itself. The evaporation behaviors of toluene and xylenes are directly dependent on the ethanol content.
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