AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Artifacts and Stability of Fine Particle Oxidative Potential Determined with Dithiothreitol (DTT) Assay on Filter Extracts
DONG GAO, Ting Fang, Vishal Verma, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 672 Working Group: Health Related Aerosols
Abstract Artifacts and stability of fine particulate matter (PM$_(2.5)) oxidative potential (OP), measured via the dithiothreitol (DTT) assay were studied. Particles were collected in urban Atlanta with high-volume samplers (HiVol, ~1.13 m$^3 min$^(-1)) and particle composition monitors (PCM, 16.7L min$^(-1)) on two different types of filter substrates, i.e. quartz and Teflon, and also with or without activated charcoal denuders. HiVol quartz filter DTT activity was in good agreement with PCM denuded quartz filters (R=0.78, N=14) and also PCM undenuded Teflon filters (R=0.94, N=13), indicating measurement of water-soluble DTT activity was unaffected by filter type or sampling method, when analyzed soon after collection. HiVol quartz filters collected in January 2015 were analyzed periodically to quantify the effects of storage time (frozen at -20 degrees Celsius) on the stability of DTT-active compounds. No significant variation in DTT activity was observed in the first half year after collection. However, the filters collected and archived (frozen at -20 degrees Celsius) in a previous campaign indicated decay in DTT activity by 53% over a period of about two years. Solid phase extraction with a C-18 column showed that the loss in DTT activity was mainly associated with the hydrophobic fraction (DTT activity driven by organic species), whereas the hydrophilic fraction (DTT activity driven by redox-active metals) was stable. These results can be used to set ROS sampling protocols and the extent to which archived filters can be used to quantify the oxidative potential of ambient aerosols for retrospective health studies.