Aerosol Fe speciation
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. Currently, there is very little information on if and how this inter-conversion can happen in the atmosphere. The significant knowledge gap not only limits our understanding of bioavailability of iron as an essential nutrient that controls oceanic productivity, and impacts the global carbon budget and climate, but also hinders the further illustration of the mechanisms of atmospheric aging effect on PM toxicity on adverse health effect. This study will combine both real world field investigation to provide evidence-based knowledge on the particle bound water soluble iron speciation, and laboratory investigation to demonstrate the impact of atmospheric processing and aging on the conversion between Fe (II) and Fe (III). The findings from this study will be 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.
Schematic diagram of the experimental setup of the LED based liquid waveguide capillary cell (LWCC) for optical absorption detection of Fe(II)
Experimental setup and diagram of various tasks