10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Evidence of Atmospheric Secondary Transformation of Transition Metals and Impact on Particle Oxidative Potential
ZHI NING, City University of Hong Kong
Abstract Number: 777 Working Group: Aerosols and Health - Connecting the Dots
Abstract Exposure to fine Particulate Matter (PM2.5) has been linked with various adverse health effects. Particle bound metals, especially transition metals, are hypothesized to initiate respiratory disease and trigger systemic inflammatory disease response. Understanding the role of metals in PM induced health effects is key to mitigate the impact of air pollution and protect public health. Iron is the most abundant PM transition metals from various sources including road dust, traffic, industrial and ship emissions. Many research studies have shown positive association between water soluble iron and the generation of reactive oxygen species (ROS) as the pathway to oxidative stress. However, the two different oxidation states of ferrous (Fe(II)) and ferric (Fe(III)) can be inter-converted in which photoreduction of Fe(III) to Fe(II) theoretically participates in a catalytic cycle to produce toxic hydroxyl radicals (·OH) and Fe(II) can also be oxidized to Fe(III) by molecular oxygen to generate superoxide anion O2- while Fe(III) plays an important role in various redox reactions. This study combines both real world field investigation to provide evidence-based knowledge on the particle bound water soluble iron speciation, and laboratory investigation to evaluate the impact of atmospheric processing and aging on the conversion between Fe (II) and Fe (III). Clear evidence was found in the atmospheric transformation of the transition metal of iron during day and evening times, same with the laboratory controlled UV exposure experiments. Controlled tests and spike tests with addition of ironic components showed their positive contribution to the overall oxidative potential of aerosols. The reactive oxygen species generated from the fresh and secondary formed aerosols also showed clear difference suggesting the strong impact of transformation of transition metals on the health implications. This study is one of the first investigations of its kind, and we expect the results will form the basis to better understand the relation between particle metals and health effects.