Impact on ground-level ozone formation by emission characterization of volatile organic compounds from a flex-fuel light-duty vehicle fleet in a traffic tunnel in Rio de Janeiro, Brazil

Abstract

The present study aimed to evaluate the contribution of mobile source emissions from, in particular, light-duty vehicles (LDVs) to tropospheric ozone formation in the Rio de Janeiro Metropolitan Area (RJMA), by quantifying the volatile organic compounds (VOCs) in a representative urban road tunnel of the city. The importance of having this type of study in Brazil is because this country has a unique vehicle emission scenario that passenger cars can use different percentages of bioethanol mixed in gasoline. The concentration of speciated VOCs in Reboucas tunnel in Rio de Janeiro, Brazil, was measured in two campaigns, total period of eight weekdays, and the VOC determination was used to calculate the average composition of the emissions of Rio de Janeiro’s LDV fleet. The United States Environmental Protection Agency (US EPA) method TO-15 was applied to determine the concentrations of VOCs C3–C12. It was found that the vehicles circulating through the tunnel were predominantly light-duty flex-fuel cars (99%). The VOC profile was constant in the monitored period. The most abundant compounds were, in order, propane, iso-pentane, n-pentane, propene, and n-butane. In addition, mono-aromatic compounds were found to be the VOC class with the highest ozone-forming potential (OFP), while propene was the main VOC contributor to ozone formation, being responsible for 27% of the troposphere ozone formed by the total VOCs monitored in the present study.