Understanding the sources and atmospheric processes of soluble iron in aerosols using a synergistic measurement approach

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1853/42859

Title: Understanding the sources and atmospheric processes of soluble iron in aerosols using a synergistic measurement approach
Author: Oakes, Michelle Manongdo
Abstract: This thesis focuses on the characterization of soluble iron in ambient/urban and source emission aerosols, primarily focusing on the sources and atmospheric processes contributing to iron solubility. Multiple techniques, including bulk and single particle measurements, were used to investigate the complex chemistry of iron solubility. A technique was developed and validated (PILS-LWCC), allowing for 12-minute measurements of water-soluble ferrous iron (WS_Fe(II)) in aerosols with a limit of detection of 4.6 ng m-3 and 12% relative uncertainty. The PILS-LWCC was deployed at several urban field sites (Atlanta, GA and Dearborn, MI) and a biomass burning event to determine major sources and atmospheric processes of WS_Fe(II) in aerosols. PILS-LWCC measurements suggest that industrial and biomass burning are sources of WS_Fe(II). In addition, acid-processing mechanisms also appeared to influence WS_Fe(II) concentrations, based on a strong correlation between WS_Fe(II) and SO42- (r2 = 0.76) as well as apparent aerosol acidity (r2 =0.78) during a field campaign in Atlanta, GA. Synchrotron-based techniques, such as X-ray Absorption Near-Edge Structure (XANES) spectroscopy and micro X-ray fluorescence measurements, were also used to identify the chemical composition (redox state and phase) and mixing state (two properties that may influence iron solubility) of source emission and ambient single iron-containing particles. These single particle measurements were used in conjunction with bulk iron solubility to assess the influence of chemical composition and mixing state on iron solubility. Single particle (synchrotron-based) and bulk iron solubility measurements suggested that iron solubility is not primarily driven by chemical composition in source emission and ambient particles. Differences in iron solubility, however, were related to single particle sulfur content in ambient and source emission aerosols, suggesting that similar sources/atmospheric processes control iron solubility in these samples. The relationship between iron solubility and sulfur content corresponded well with bulk ground-based measurements of ambient aerosol using the PILS-LWCC. Combined single particle and bulk online measurements provide compelling evidence that atmospheric acid processing, involving sulfur-containing acids (H2SO4), is an important formation route of soluble iron in ambient urban aerosols. The results of this thesis provide valuable information to further understanding the controls of iron solubility in atmospheric aerosols.
Type: Dissertation
URI: http://hdl.handle.net/1853/42859
Date: 2011-11-08
Publisher: Georgia Institute of Technology
Subject: Soluble iron
Synchrotron-based technology
Online measurements
Atmospheric aerosols
Atmospheric chemistry
Department: Earth and Atmospheric Sciences
Advisor: Committee Chair: Weber, Rodney; Committee Co-Chair: Ingall, Ellery; Committee Member: Bergin, Micheal; Committee Member: Rusell, Armistead; Committee Member: Shafer, Martin
Degree: PhD

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