AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
The Effect of NO gas on the Solubility of Dust-Borne Iron
MUNKHZAYA BOLDBAATAR, Brian Majestic, University of Denver
Abstract Number: 616 Working Group: Urban Aerosols
Abstract Despite being the most abundant element on the Earth’s crust and atmosphere, iron is the limiting micronutrient for phytoplankton due to its highly water-insoluble nature. The most significant source of iron in the oceans is via atmospheric deposition of Aeolian dust, where the iron is < 1% soluble. In contrast, particles collected in urban settings contains 20-70% soluble iron and is estimated that, globally, 20-50% of atmospheric soluble iron is contributed from anthropogenic sources. The increase in solubility is thought to be attributed to particle size, acidification during transport, and mineralogy of the dust source. Particularly of interest is how anthropogenic gases affect the acidification of iron. Therefore, the focus here is to study the effect of a largely anthropogenic gas on the solubility of iron and to understand its paths of solubilization.
With more than half of emissions stemming from vehicles, NO is a common anthropogenic air pollutant. While previous studies on Asian dust have found nitric acid vapors to solubilize trace elements, the effects of NO have not been studied. To better understand iron solubilization and acidification during transport, we exposed dust to a constant concentration of NO in both a dry and humid environment. The PM2.5 fraction of the dust was resuspended onto Teflon filters and exposed in polypropylene vacuum desiccators for 27 hours. Post-exposure, the samples were cut in half. One half was rocked for 2-hrs in a simulated cloudwater buffer and the soluble Fe was analyzed via quadrupole ICP-MS. The other half underwent a total acid digestion and was measured for total iron. The pre- and post- exposure soluble Fe is compared to the total Fe on the filter.
Thus, in this presentation, we will present how NO affect the acidification and/or subsequent solubilization of dust-borne iron.