AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Real-Time Measurements of Direct and Catalytic Aerosol Oxidative Activity
Yupaporn Sameenoi, Meghan Mensack, Kirsten Koehler, Jeff Shapiro, Jeffrey L. Collett, John Volckens, CHARLES HENRY, Colorado State University
Abstract Number: 587 Working Group: Aerosol Exposure
Abstract Anthropogenic particulate matter significantly impacts human health, most likely through the generation of oxidative stress. Because of the chemical complexity of atmospheric aerosols, multiple pathways exist for generating oxidative stress, including both direct oxidation and catalytic oxidation where reactive oxygen species are generated by the reaction of the particulate matter with biological oxidants such as peroxide. At present, the dithiothreitol (DTT) assay is the most common method to measure direct aerosol oxidative activity. In this assay, reduced DTT is oxidized to its disulfide by particulate matter; the remaining DTT is then reacted with Ellman’s reagent and quantified by UV spectroscopy. The traditional DTT assay requires long sampling times (hours to days) such that sufficient mass is collected for analysis. Thus, many of the most reactive (and short lived) species may not be present at the end of the sampling period. The DTT assay is only capable of quantifying direct catalytic processes and does not provide the ability to measure catalytic oxidative activity. To address these problems, we have developed two novel electrochemical sensors to measure direct and catalytic aerosol oxidative activity in real time. The direct oxidative activity sensor electrochemically measures the remaining DTT present after reaction with particulate matter collected using a Particle Into Liquid Sampler (PILS). The system provides the ability to make measurements at atmospherically relevant particulate matter concentrations with high time resolution (~3 min). Measurements of oxidative activity for two laboratory-generated aerosols (fly ash and urban dust) show a strong correlation between oxidative activity and aerosol concentration. The catalytic sensor measures an aerosol’s ability to generate hydroxyl radicals by mixing particulate matter with H2O2 and a radical trapping agent, salicylic acid. On trapping of the radical, the salicylic acid is converted to dihydroxy-benzoic acid that can be easily detected electrochemically.