Fuel-based motor vehicle emission inventory for the metropolitan area of Mexico city

The level and nature of air pollution varies substantially from city to city. Hence, the first requirement is the creation of an adequate knowledge base on local air quality on which to develop an air quality policy. Because the availability of data used in traditional on-road mobile source estimation methodologies is limited in Mexico, an alternative methodology was implemented to estimate motor vehicle emissions. In the year 2000, on-road gasoline powered vehicle emissions in the Metropolitan Area of Mexico City (MAMC), were characterized using fuel sales as a measure of vehicle activity, and exhaust emissions factors from remote sensing measurements. In a similar way, remote sensing data obtained by researchers of the University of Denver back in 1991 and 1994 were used to estimate a fuel-based emission inventory for those years. Average emissions factors were estimated in 113.5±13, 13.1±1.9 and 9.84±2.3 g l−1 for CO, hydrocarbons (HC) and nitrogen oxides (NOx), respectively, based on remote sensing measurements of 42,800 vehicles. For year 2000 light and medium gasoline vehicles exhaust emissions contributed with 2065, 238, and 179 metric ton day-1 of CO, HC and NOx, respectively. The inventory is 48% and 26% lower in CO and NOx, respectively, than official inventory estimates for the year 1998 using travel-based models. Calculated CO reduction from 1991 to 1994 is approximately 46% while the atmospheric CO measurements, as indicator of mobile activity, in the same period decrease 51%. For the period 1994-2000 the reductions were 36% and 31%, respectively. The calculations indicate a continually decreasing inventory over the study period, and represents and ideal alternative for locations such as Mexican cities lacking the resources to develop an emissions model.