Contribution of soil, sulfate, and biomass burning sources to the elemental composition of pm[10] from Mexico City

ABSTRACT

This study is aimed to identify sources of particulate matter with mean aerodynamic diameter below 10 microm [PM[10]] present in the atmosphere of the Metropolitan Area of Mexico City [MAMC], using samples obtained from January 1st to June 30th, 2009, analyzed with X-ray spectrometric techniques. MiniVol samplers were used to collect samples on polycarbonate filters in three sites [North, Center, and South] of the MAMC. The filters were exposed along 24 h every two days, starting at 800 AM, and then analyzed with particle induced X-ray emission [PIXE], a microPIXE [microPIXE] system, and X-ray fluorescence [XRF]. Statistical multivariate tests with positive matrix factorization [PMF] were conducted to identify possible contributing factors. The model HYSPLIT was used to determine back-trajectories and the MODIS database for fire spot localization. The multivariate methods identified five factors in the Center and South, and four in the North, including Soil, Sulfate, Fuel/Industry, and Biomass burning, with certain differences in the factors and contributions. Application of HYSPLIT back-trajectories associated these factors to three main Soil sources and points of secondary aerosols production, as well as locations where Biomass burning aerosols were originated. The combination of X-ray spectrometric methods, receptor modeling, back-trajectory determination, and fire site localization, allowed the identification of possible sources of PM[10] in the MAMC, namely, the dry Texcoco lake, the Toluca Valley, and the North dry plains for Soil aerosols, the influence of local industrial areas for Sulfate [secondary] aerosols, and the appearance of fires for Biomass burning