10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
PRAPPE: Influence of Iron on the Photoaging of Particulate Matter in the Environment
FRANK LERESCHE, Joseph Salazar, David Pfotenhauer, Michael Hannigan, Brian Majestic, Fernando Rosario-Ortiz, University of Colorado, Boulder
Abstract Number: 846 Working Group: Aerosol Chemistry
Abstract Particulate Matter (PM2.5) are produced by a variety of processes (e.g. from anthropogenic activities such as road emissions but are also emitted from natural sources) and are a particularly important research topic due to their detrimental impacts on human health. We present here investigations on the photoaging of these PM2.5 in the aqueous phase and particularly on the influence of iron on the generation of hydroxyl radicals (OH•) that are one of the major species driving to the photoaging of the PM2.5. OH• being produced in PM extracts under irradiation through the Photo-Fenton reaction, nitrate photolysis and from the dissolved organic matter.
A sampling campaign called PRAPPE (Platte River Air Pollution and Photochemistry Experiment) investigating the properties of PM2.5 coming from an urban, a rural and a mixed urban-rural site was done in the Denver area, Colorado. Characterization of the Iron speciation in the different sites as well as the measure of the total and soluble metals was the subject of another abstract. The focus of this abstract is on the photoaging mechanisms that drive the fate of PM2.5 in aqueous phase and on the influence of Iron on the photoaging. The optical properties, such as the absorbance and fluorescence, and the capability of the PM2.5 aqueous extracts to generate hydroxyl radical under simulated sunlight were investigated. Furthermore, the effects of solar irradiation were further explored by submitting the PM2.5 extracts to simulated sunlight, artificially photoaging them. The observed light absorbance capacity was higher in the urban site than in the rural one and it was observed that the decrease in light absorbance properties during photoirradiation was correlated with the iron content of the extracts. The observations correspond to a scenario were the PM2.5 are mostly produced in the urban site and are transported to the rural one, with a mean age of the PM2.5 higher in the rural site.
This work should help to understand the parameters that influence the photoaging of PM2.5 in the atmosphere, as well as the influence of trace elements on this process.