Document Type

Thesis

Date of Degree Completion

Spring 2017

Degree Name

Master of Science (MS)

Department

Chemistry

Committee Chair

Dr. Anne Johansen

Second Committee Member

Dr. Dion Rivera

Third Committee Member

Dr. Anthony Diaz

Abstract

Ferrous iron (Fe(II)) has been implicated as one contributor in the generation of reactive oxygen species (ROS) from ambient particles emitted during the incomplete combustion of fossil and biomass fuels. Although ROS are known to induce unhealthy oxidative stress in cellular systems, the mechanisms of Fe(II) formation and stabilization in aerosol particles are still not well understood. Here, we investigate the role of soot on Iron reduction from Fe(III) to Fe(II), under various conditions including those encountered in the tailpipe of a vehicle. Aqueous leaching experiments of soot-hematite mixtures were carried out while analyzing for Fe(II) spectrophotometrically, and changes in Fe(II) concentrations were then investigated in the context of soot characteristics, including surface area, surface functional groups, and soot structure. Results show that some soot-iron mixtures have a synergistic effect on the reduction of Fe(III), representing between 0.001% to 0.30% Fe(II) of total Fe within the first 120 min of the experiment and up to 0.82 % Fe(II) after 48 hours or extraction. Extent of reduction depends on type of soot and its pre-treatment. Exposure to light did not significantly change Fe(II) production in soot-hematite mixtures. These results indicate that, during night-time, the production and stabilization of Fe(II) by soot can significantly contribute to total Fe(II) concentrations in ambient aerosol particles.

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