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Size Fractionation of PM2.5 Water-soluble Elements (Iron and Copper) and Oxidative Potential
YUHAN YANG, Dong Gao, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 51
Working Group: Health-Related Aerosols
Abstract
Epidemiological studies have established a link between particulate matter (PM) mass and adverse health-related issues. Particle oxidative potential (OP), referring to the redox ability of PM, is a possible unifying concept that connects a host of adverse health effects. Iron (Fe) and copper (Cu) are often the most abundant transition metals in ambient PM2.5 and are important contributors to aerosol OP. A number of studies have shown water-soluble metals are especially toxic, compared to insoluble metal species. In this study, we developed robust liquid spectrophotometric methods for measuring total and soluble Fe and Cu with a single relatively inexpensive analytical system. These methods were applied to 24-hour filter samples collected throughout the year 2017 in urban Atlanta. The water-soluble components, operationally defined as those species in the aqueous filter extract that pass through a 0.45 µm filter, were further characterized by ultrafiltration, which showed that roughly 85% of both the Fe and Cu in the water-soluble fraction was composed of species smaller than nominally 4 nm. For Fe, roughly 23% was in the nominal size range of 2 to 4 nm, whereas for Cu almost all were smaller than 2 nm. OP of the water-soluble fractions is characterized by measured redox potential in simulated epithelial lining fluid. Our results indicate that water-soluble Fe and Cu are composed of dissolved species or very small colloidal particles that are highly reactive and could be important contributors to aerosol OP.