10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
PRAPPE: Trace Element Interaction with Organic Compounds in Urban and Crustal PM
JOSEPH SALAZAR, David Pfotenhauer, Frank Leresche, Fernando Rosario-Ortiz, Michael Hannigan, Brian Majestic, University of Denver
Abstract Number: 1168 Working Group: Aerosol Chemistry
Abstract As part of a larger study, we present field data from the Platte River Air Pollution and Photochemistry Experiment (PRAPPE), aimed at understanding the interactions between organic carbon and trace elements in atmospheric particulate matter (PM). One transformation pathway of organics in the atmosphere is radical oxidation. One possibly unexplored route of radical formation is iron in aqueous suspension via the Photo-Fenton reaction. In Fenton Chemistry, UV light reacts with iron (III) to produce iron (II) and hydroxyl radicals. In turn, the hydroxyl radicals oxidize organic compounds. In this portion of the study, we investigate the role of metals in this process by collecting simultaneous PM2.5 samples in three regions: urban, rural, and a mixture between the two. Sampling was accomplished during the summer (Aug. 2017) and winter (Dec. 2016 - Mar. 2017), where 24-hr PM2.5 samples were collected at three different sites on the Eastern Colorado plains. At each site, three filters were collected: two Teflons (mass, ions, soluble metals, and total metals) and 1 quartz filter (EC/OC and organic speciation). Part of the Teflon filter was also analyzed by x-ray absorption near edge structure (XANES) spectroscopy to probe the oxidation state of iron in the PM. Understanding the oxidation state of the iron is an important factor in determining its solubility, where Fe(II) tends to be the more soluble of the iron species, and thus would be most important in radical production. In addition, XRF maps of each sample were collected to understand intraparticle composition. During the winter, the urban and mix site showed the same levels of iron concentration (average = 2.70 ng/m3) while the crustal site showed significantly less iron (average = 0.78 ng/m3). This is one of two abstracts for this project. Here, we work to quantify and understand the state of iron in the different sources of PM while another abstract will present data on the influence of iron on the formation of hydroxyl radical upon photoirradiation of aqueous PM extracts and on the effect of irradiation on the light absorbance properties and hydroxyl radical formation potential of the extracts. These results will be the first attempt in the understanding how iron processes organic compounds through reactive oxygen species in PM collected from urban and rural sources.