Spectromicroscopic Studies of the Aging of Carbonaceous Aerosols from Mexico City

Milagro, a multi-national atmospheric field campaign, was conducted in Mexico City during March of 2006. Aerosols were collected at three ground based sites, situated progressively farther from the city center. These aerosol samples are studied with computer controlled scanning electron microscopy with energy dispersive X-ray analysis (CCSEM/EDX) and scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). This presentation focuses on evidence for carbonaceous aerosol transformation examining aerosol composition, C/O atomic ratios, mixing states, and changes in carbon bonding over time and distance from the source.