Document Type

Thesis

Date of Degree Completion

Spring 2019

Degree Name

Master of Science (MS)

Department

Chemistry

Committee Chair

Anne Johansen

Second Committee Member

Yingbin Ge

Third Committee Member

Dion Rivera

Abstract

The emission of ambient particulate matter (PM) is regulated by many institutions due to the detrimental effects on health, environment and climate; yet many underlying mechanisms of PM reactivity are still not well understood. In the current study, the effect of carbonaceous nanoparticles (CNPs), contained within ultrafine PM (particle diameter ≤ 100 nm), is investigated on naturally occurring processes that increase the abundance of bioavailable iron. Enhancing iron bioavailability (i) increases primary productivity of iron-limited microorganisms, affecting the carbon cycle and global climate, and (ii) increase toxicity of inhaled particles through the associated production of reactive oxygen species (ROS). Specifically, the ferric iron (Fe(III))-oxalate complex is investigated as it is known to be a major source of bioavailable ferrous iron (Fe(II)) in natural environments. To mimic aerosol particles, acidic aqueous slurries of ferrihydrite, as the Fe(III) source, were exposed to oxalate and various types of CNPs in dark and light experiments. Throughout the 4-24 hour experiments, Fe(II) and reducible-Fe(III) were determined colorimetrically using UV-Vis spectrophotometry, while oxalate was quantified by Ion Chromatography (IC). Results indicate that CNPs enhances the production of Fe(II) from Fe(III)-oxalate by a factor of 2 in dark and 5 in light experiments. The maximum fractional iron dissolution of 11% of total iron was observed for diesel soot in light which constitutes a significant enhancement in iron bioavailability. Physico-chemical characterization of CNPs including surface area, adsorption properties and structure did not reveal a clear relationship iv toward reactivity. Overall, results help explain the larger contribution of iron solubility observed in collected combustion derived particles compared to dust-derived particles with implications on global climate and human health.

Available for download on Saturday, June 15, 2024

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