Quantification of primary PM2.5 Mass Exchange in three Mexican Megalopolis Metropolitan Areas

It is commonly assumed that the outgoing flux of pollutants from large cities deteriorates the air quality of neighboring communities. Quantifying the mass exchange of pollutants among cities will enable local and regional planning of environmental management programs, to identify well all previously unrecognized impacted areas. In this study, the quantification of outgoing and incoming fluxes of primary PM2.5 particle mass among three neighboring metropolitan areas of the Mexico City Megalopolis in the dry-cold climate months, was carried out for the first time. The results show that the metropolitan areas of Toluca Valley and Cuernavaca receive mass quantities of PM2.5 approximately equivalent to a 100% of their local emissions. The prevailing winds in the cold-dry climate months, impel the emissions from the studied metropolitan areas, effectually dispersing in different directions, though mainly towards the megalopolis South, impacting with large mass amounts of PM2.5 the rural areas. The overlap puffs of local emissions with imported particle masses contribute to atypically high concentration events in receiving metropolitan areas. In the import-export balance, the metropolitan areas of Toluca and Cuernavaca had a significant PM2.5 concentration increasing during the cold-dry climate months mainly due to the incoming particles from the Mexico City Metropolitan Area.