Dissertation
The impacts of fungi on trace organic contaminant fate in stormwater bioretention cells
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2022
DOI: 10.25820/etd.006729
Abstract
Stormwater contains a complex mixture of contaminants due to the myriad of nonpoint sources including lawns/parks, buildings, and roads. Of particular concern are trace organic contaminants within stormwater, including pharmaceuticals, pesticides, and tire wear compounds formed from abrasion of tires with road surfaces. These trace organic contaminants can have adverse effects on aquatic and terrestrial life, and hydrophilic/polar compounds can be difficult to treat via physical removal such as sorption. Thus, there is a need to explore existing stormwater management approaches and methods for improvement to address the growing number of trace organic contaminants found in stormwater. One option of stormwater management is green stormwater infrastructure such as permeable pavement, green roofs, bioswales, and bioretention cells. These systems are primarily designed to reduce peak runoff volume, quickly infiltrate stormwater, and effectively return the hydrologic regime to a state close to “pre-development”. The systems of focus for this work are bioretention cells, which contain an engineered sandy soil mix and are often planted. Bioretention cells have both abiotic and biotic methods of contaminant removal and transformation. Given the increasing prevalence of trace organic contaminants, there is a great need to assess the adequacy of both abiotic and biotic methods of trace organic contaminant removal. Abiotic sorption can be enhanced within bioretention cells through the inclusion of novel soil amendments such as biochar (black carbon amendments that can be highly sorptive). However, contaminants can pass through the cell once sorption capacity reaches a maximum. Thus, there is a need to evaluate how biotic removal not only increases abiotic sorption capacity, but aids in contaminant transformation with the goal of detoxification.
Plant and bacterial biotransformation in bioretention cells have received some limited attention in the literature, but there are remarkably few studies on the role of fungi in bioretention cells. Fungi are a diverse group of organisms; mycorrhizal fungi often grow in mutually beneficial relationships with plants, and white/brown-rot fungi have demonstrated exceptional contaminant degradation abilities. Nonetheless, the various potential benefits fungi could offer within bioretention cells remain unexplored. This work addresses the knowledge gap concerning the impacts of fungi on trace organic contaminant fate in stormwater bioretention cells through two studies. The first study in this work investigated fungal removal and transformation of two relevant trace organic stormwater contaminants, the tire wear compounds acetanilide and hexamethoxymethylmelamine. White rot fungi were found to significantly remove and transform the tire wear compounds acetanilide and hexamethoxymethylmelamine by 81.9% and 69.6%, respectively. Additionally, 20 transformation products of hexamethoxymethylmelamine and three products of acetanilide were identified, including melamine as a potential dead-end product of hexamethoxymethylmelamine and a novel glutamine-conjugated product of acetanilide. The second study examined fungal diversity and key fungal functional gene abundance within 28 eastern Iowa bioretention cells. We found that differences in fungal diversity are well-explained by both the primary plant type within the cell as well as the presence/absence of native grasses and forbs. Fungal laccases and a nitrite reductase gene were quantified within the cells and abundances of these genes were significantly correlated with soil pH and percent organic matter. Altogether, these chapters contribute to understanding of trace organic contaminant removal in bioretention cells by demonstrating contaminant removal/transformation and exploring fundamental questions of fungal functional and taxonomic diversity.
In addition to experimental research, one chapter of this dissertation is dedicated to education research about graduate technical communication skills and how skills are influenced by a proposal-writing project implemented in a technical course. We demonstrated successful implementation of an advanced technical writing project in a required graduate course and provided insight into the need to train graduate students in communication skills such as creating testable hypotheses and communicating science to a broad audience. This education research was made possible in part from the integration of career development into the Sustainable Water Development program, where trainees were encouraged to pursue professional development opportunities outside of their core research focus.
Details
- Title: Subtitle
- The impacts of fungi on trace organic contaminant fate in stormwater bioretention cells
- Creators
- Erica Akari Wiener
- Contributors
- Gregory LeFevre (Advisor)Bin He (Committee Member)Craig Just (Committee Member)Timothy Mattes (Committee Member)Jerald Schnoor (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Summer 2022
- DOI
- 10.25820/etd.006729
- Publisher
- University of Iowa
- Number of pages
- xxiii, 229 pages
- Copyright
- Copyright 2022 Erica Akari Wiener
- Language
- English
- Description illustrations
- Illustrations, charts, graphs, tables
- Description bibliographic
- Includes bibliographical references.
- Public Abstract (ETD)
Whenever it rains, the resulting stormwater flows over buildings, lawns, and streets, collecting a variety of man-made chemicals. Some of these chemicals are known (e.g., weed/insect-killers), but new chemicals have been identified, including chemicals found in tires. This complex mixture of chemicals can be transported into storm drains or nearby soil, rivers, and lakes, posing a risk to fish or even humans who use the water downstream.
”Green stormwater infrastructure” is a term for systems that manage stormwater; some stormwater chemicals can be removed by these systems. For example, bioretention cells contain mostly sandy soil and are usually planted; chemicals can attach to or be filtered by the soil. Additionally, chemicals can be removed by the plants and microbes (bacteria and fungi) that live in such systems. However, little is known about the types of fungi present in these systems and if/how fungi remove stormwater chemicals, even though fungi have demonstrated remarkable abilities to remove pollutants that other organisms are unable to break down.
In this work, we investigate the ability of fungi to remove newer stormwater pollutants called tire wear compounds, which are released from tiny rubber particles that come off of tires when driving. We found white rot fungi (a certain type of fungi), were able to break down key tire wear compounds. We also determined the different kinds of fungi living in bioretention cells by sampling the soil and identifying the fungi living within the soil. To understand how fungi interact with chemicals in stormwater, we measured the amount of specific genes present in the soil that were related to fungal processes that might alter or remove stormwater chemicals.
Finally, my graduate program fully supported professional development in the form of “Path Training Experiences”- career training opportunities to help prepare trainees for their desired career path. I published a paper on advanced communication training for graduate students, and how using a scientific proposal as a course project helped strengthen technical communication skills such as sharing scientific work with broad audiences. This publication provides a framework for educators to use in their own coursework and highlights the importance of formal training in communication skills.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984285051002771
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