Contribution of the gasoline distribution cycle to volatile organic compound emissions in the metropolitan area of Mexico City.

Gasoline distribution in the metropolitan area of Mexico City (MAMC) represents an area of opportunity for the abatement of volatile organic compound (VOC) emissions. The gasoline distribution in this huge urban center encompasses several operations: (1) storage in bulk and distribution plants, (2) transportation to gasoline service stations, (3) unloading at service stations' underground tanks, and (4) gasoline dispensing. In this study, hydrocarbon (HC) emissions resulting from breathing losses in closed reservoirs, leakage, and spillage from the operations just listed were calculated using both field measurements and reported emission factors. The results show that the contribution of volatile HC emissions due to storage, distribution, and sales of gasoline is 6651 t/year, approximately 13 times higher than previously reported values. Tank truck transportation results in 53.9% of the gasoline emissions, and 31.5% of emissions are generated when loading the tank trucks. The high concentration of emissions in the gasoline transportation and loading operations by tank trucks has been ascribed to (1) highly frequent trips from distribution plant to gasoline stations, and vice versa, to cope with excessive gasoline sales per gasoline station; (2) low leakproofness of tank trucks; and (3) poor training of employees. In addition, the contribution to HC evaporative and exhaust emissions from the vehicles of the MAMC was also evaluated.