Abstract View
Increased Temporal Resolution of Environmentally Persistent Free Radicals (EPFR) in Atmospheric Particulate Matter and Combustion Particles via Electron Paramagnetic Resonance (EPR) Spectroscopy
HEATHER RUNBERG, Deborah Mitchell, Sandra Eaton, Gareth Eaton, Brian Majestic, University of Denver
Abstract Number: 303
Working Group: Instrumentation and Methods
Abstract
Environmentally persistent free radicals (EPFRs) are an emerging area of atmospheric interest due to their implications in adverse health effects. Previous EPFR studies have looked at 24-hour averages of EPFR concentration within ambient PM2.5, however, because PM2.5 levels vary diurnally there is a need for higher resolution monitoring. This study demonstrates instrumental sensitivity that is adequate to assess EPFR concentrations at a much higher temporal resolution than previously reported. Ambient PM2.5 samples were collected for 90 minutes at 96 L min-1 and analyzed quantitatively via electron paramagnetic resonance (EPR) spectroscopy. Environmental samples had no measurable PM2.5 mass, to a sensitivity of ±10µg, however EPFR concentrations were found in the range of 1012 spins m-3 of air sampled, which is similar to values that have been reported previously in other urban locations, using longer sample collection periods. Additionally, because combustion products are likely to contribute to the EPFR portion of PM2.5, and understanding how they are impacted by environmental conditions is necessary for interpreting the results of environmental samples, hexane generated soot was assessed for radical stability when exposed to water and ambient atmospheric conditions. Radical concentrations decreased by about 5% over the course of 88 days, but there was no difference in degradation rates between wetted and non-wetted soot. This study highlights the potential for sub-hourly EPFR monitoring which would allow for better insight into human exposure.