Contribution of garbage burning to chloride and PM _2.5 in Mexico City

The contribution of garbage burning (GB) emissions to chloride and PM _2.5 in the Mexico City Metropolitan Area (MCMA) has been investigated for the period of 24 to 29 March during the MILAGRO-2006 campaign using the WRF-CHEM model. When the MCMA 2006 official emission inventory without biomass burning is used in the simulations, the WRF-CHEM model significantly underestimates the observed particulate chloride in the urban and the suburban areas. The inclusion of GB emissions substantially improves the simulations of particulate chloride; GB contributes more than 60% of the observation, indicating that it is a major source of particulate chloride in Mexico City. GB yields up to 3 pbb HCl at the ground level in the city, which is mainly caused by the burning of polyvinyl chloride (PVC) in the garbage. GB is also an important source of PM _2.5, contributing about 3-30% simulated PM _2.5 mass on average. More modeling work is needed to evaluate the GB contribution to hazardous air toxics, such as dioxin, which is found to be released at high level from PVC burning in laboratory experiments.