Effect of Iron-Containing Mineral Dust on Photodegradation of Secondary Organic Aerosols

ANTHONY JUE, Sergey Nizkorodov, University of California, Irvine

     Abstract Number: 655
     Working Group: Aerosol Chemistry

Abstract
Mineral dust acts as a source of transition metals in the atmosphere. Iron is a common component in mineral dust particles, for example, in the form of hematite, iron (III) oxide. Secondary organic aerosol (SOA) compounds can react with iron and the oxidizers it produces by photocatalysis and/or Fenton chemistry. These photo-catalyzed reactions can result in changes to the SOA molecules, from oxidation to smaller compounds to oligomerization. To better characterize the effect of iron containing particles on SOA, hematite and Arizona Test Dust (ATD) are mixed with SOA particles and variable amounts of water, and irradiated with UV light. SOA is generated via flow tube ozonolysis of monoterpenes or photooxidation of aromatic compounds. For aqueous phase experiments, an SOA sample is extracted in water and photoaged to simulate several hours of solar irradiation, with a similar sample being aged in the presence of either hematite or ATD as a slurry, then filtered and analyzed via UPLC-HRMS to identify any major differences in the product profile after photoaging. For dry experiments, SOA is extracted in an organic solvent, Fe-containing particles are added, and the suspension is evaporated to dryness, leaving a film which can be similarly irradiated and the resulting photoaged film redissolved and similarly analyzed by UPLC-HRMS.