Dissertation
Development of the polyurethane foam passive air sampler for novel applications in ambient air across the globe
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2018
DOI: 10.17077/etd.nl4po2cl
Abstract
<p>Our understanding about the presence, behavior, and toxicities of atmospheric persistent organic pollutants is limited by our ability to accurately measure them. This dissertation details the development and characterization of a model for the determination of an accurate sampling rate (R<sub>s</sub>), and effective sampling volume (V<sub>eff</sub>), for polyurethane equipped passive air samplers (PUF-PAS), and the subsequent application of PUF-PAS sampling methods towards novel applications studying polychlorinated biphenyls (PCBs).</p>
<p>The user friendly mathematical model resulting from this work, published as a Matlab script, predicts R<sub>s</sub> and V<sub>eff</sub> as a function of local hourly meteorology and the physical-chemical properties of the target analytes. The model was first developed using active sampling methods in urban Chicago, where good agreement was found between the PUF-PAS and high volume active samplers: Active/Passive = 1.1 ± 1.2. The model was then expanded and calibrated globally using the dataset from the Global Atmospheric Passive Sampling (GAPS) network. After this global calibration we found acceptable agreement between modelled and depuration-determined sampling rates for an independent dataset, with several compounds having near zero mean percent bias (±6%). The globally applicable model is the best alternative for locations experiencing low average wind speeds or cold temperatures, and is particularly useful for the interpretation of samples with long deployments, deployments conducted under warming conditions, and compounds with high volatility. An interactive web-based graphical user interface for the sampling rate model was developed. Users input sampler locations, deployment dates, and target chemicals, in the web-interface and are provided with a sample and compound specific R<sub>s</sub> and V<sub>eff</sub>.</p>
<p>The sampling rate model was examined for use in the indoor environment and it was found that both the experimentally calibrated (1.10 ± 0.23 m<sup>3</sup> d<sup>-1</sup>) and modeled (1.08 ± 0.04 m<sup>3</sup> d<sup>-1</sup>) Rs agreed with literature reports. Correlating sample specific wind speeds with uptake rates, it was determined that variability of wind speeds throughout the room significantly (<em>p-value</em> < 0.001) affected uptake rates. Despite this, the PUF-PAS concentration measurements using modelled R<sub>s</sub> values were within 27% of the active sampling determined concentration measurements.</p>
<p>Using PUF-PAS samplers, PCBs 47, 51, and 68 were found to account for up to 50% of measured indoor sum PCB concentration (2700 pg m<sup>-3</sup>). Direct surface measurements were conducted to identify finished cabinetry to be a major source, as a result of the decomposition of 2,4-dichlorobenzoyl peroxide used as an initiator in free-radical polymerization of polyester resins. While this phenomenon has been detected at trace levels in other polymer products, it has never been shown to be a significant environment source of PCBs.</p>
<p>PUF-PAS samplers were similarly used to study the presence of airborne hydroxylated polychlorinated biphenyls (OH-PCBs) and PCBs in the metropolitan Chicago area. While OH-PCBs have been hypothesized to be an important removal mechanism for atmospheric PCBs, they were not directly measured in the air until recently. The two most frequently detect OH-PCB congeners in this study, 2OH-PCB2 and 6OH-PCB2, were detected at levels comparable to a previous report of atmospheric OH-PCBs utilizing active sampling methods, suggesting the viability of PUF-PAS methods to study atmospheric OH-PCBs. One sampling site detected as many as 50 OH-PCBs but uncertainties with sampling and laboratory methods prevent any strong conclusions from being drawn.</p>
Details
- Title: Subtitle
- Development of the polyurethane foam passive air sampler for novel applications in ambient air across the globe
- Creators
- Nicholas John Herkert - University of Iowa
- Contributors
- Keri C. Hornbuckle (Advisor)Gregory R. Carmichael (Committee Member)Tom Harner (Committee Member)Andres Martinez (Committee Member)Scott N. Spak (Committee Member)Charles O. Stanier (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Spring 2018
- DOI
- 10.17077/etd.nl4po2cl
- Publisher
- University of Iowa
- Number of pages
- xxi, 272 pages
- Copyright
- Copyright © 2018 Nicholas John Herkert
- Language
- English
- Date submitted
- 09/05/2018
- Description illustrations
- illustrations (some color), color maps
- Description bibliographic
- Includes bibliographical references (pages 105-120).
- Public Abstract (ETD)
Our understanding of airborne toxins is limited by our ability to accurately and conveniently measure them. This dissertation details the development of a model to accurately and conveniently predict the sampling rate of a passive air sampling device to measure air toxins. The simple and user-friendly model was developed using passive air sampling devices placed around the world, ensuring the model can be used freely by researchers and citizen-collaborators to assess the air toxins anywhere in the world.
With the growing concern around air toxins present inside buildings, including schools, it was important to also develop this model to apply indoors. A series of experiments were conducted to understand the performance of the model indoors. The model was found to produce concentration estimates of air toxins, such as polychlorinated biphenyls (PCBs), at comparable levels to traditional sampling method inside buildings.
The model and passive air sampling device was used to study the presence of air toxins in the air at residential homes in Iowa. Surprisingly high air concentrations of several PCBs not expected to be in the air were found. The wood sealant used on the kitchen cabinets was, for the first time, identified as the source of these neurotoxic and carcinogenic compounds to the air. The model and passive air sampling device were further used to identify the widespread presence of a breakdown product of PCBs in the air of the City of Chicago.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9983776835202771
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