Investigations around a gasoline service station to assess Volatile Organic Compounds (VOCs) evaporative processes and related impact on air quality at nearby residential buildings

This study aims to assess the impact of VOCs release from a gasoline service station, equipped with Stage I and Stage-II vapor recovery systems, on multiple receptor sites (n. 5 outdoor, n. 1 indoor) spatially distributed at different distances in the surroundings in a medium-sized city in the South of Italy. The methodological approach was based on the integration of: a) an extensive preliminary real-time monitoring campaign of Total VOCs (TVOCs) to detect short-term emission events; b) two consecutive 3-days air sampling campaigns addressed to chemical characterization, discrimination between contributions as well as VOCs intrusion indoors. The site at close proximity to the underground storage tank/vent pipes system (13 m) was affected by TVOCs peak concentrations and exhibited higher concentrations of benzene (2.9-4.2 μg/m3), toluene (5.3-6.2 μg/m3) and MTBE (6.9-16.0 μg/m3), up to one order of magnitude higher than those measured at higher distance, in a spatial boundary from 63 to 180 m, where traffic contribution was predominant. Therefore gasoline working losses at nozzles and storage tank along with vent pipes ‘breathing’ may provide a significant contribution to VOCs airborne concentrations in the immediate surroundings. The highest TVOCs concentration were registered when underground tank loading occurred. Diagnostic ratios MTBE/B and MTBE/T at closest sites are indicative of gasoline evaporation and I/O ratios for the main VOCs highlight intrusion indoors, posing attention on the potential inhalation exposure (high impact/short-term exposure) of the nearby population and the need for a ‘safety distance’ of residential buildings, even though the vapor recovery systems are implemented.