Browsing by Author "Ferguson, P Lee"

Oil spills in marine environments often damage marine and coastal life if not remediated rapidly and efficiently. In spite of the strict enforcement of environmental legislations (i.e., Oil Pollution Act 1990) following the Exxon Valdez oil spill (June 1989; the second biggest oil spill in U.S. history), the Macondo well blowout disaster (April 2010) released 18 times more oil. Strikingly, the response methods used to contain and capture spilled oil after both accidents were nearly identical, note that more than two decades separate Exxon Valdez (1989) and Macondo well (2010) accidents.

The goal of this dissertation was to investigate new advanced materials (mechanically strong aerogel composite blankets-Cabot® Thermal Wrap™ (TW) and Aspen Aerogels® Spaceloft® (SL)), and their applications for oil capture and recovery to overcome the current material limitations in oil spill response methods. First, uptake of different solvents and oils were studied to answer the following question: do these blanket aerogel composites have competitive oil uptake compared to state-of-the-art oil sorbents (i.e., polyurethane foam-PUF)? In addition to their competitive mechanical strength (766, 380, 92 kPa for Spaceloft, Thermal Wrap, and PUF, respectively), our results showed that aerogel composites have three critical advantages over PUF: rapid (3-5 min.) and high (more than two times of PUF’s uptake) oil uptake, reusability (over 10 cycles), and oil recoverability (up to 60%) via mechanical extraction. Chemical-specific sorption experiments showed that the dominant uptake mechanism of aerogels is adsorption to the internal surface, with some contribution of absorption into the pore space.

Second, we investigated the potential environmental impacts (energy and chemical burdens) associated with manufacturing, use, and disposal of SL aerogel and PUF to remove the oil (i.e., 1 m3 oil) from a location (i.e., Macondo well). Different use (single and multiple use) and end of life (landfill, incinerator, and waste-to-energy) scenarios were assessed, and our results demonstrated that multiple use, and waste-to-energy choices minimize the energy and material use of SL aerogel. Nevertheless, using SL once and disposing via landfill still offers environmental and cost savings benefits relative to PUF, and so these benefits are preserved irrespective of the oil-spill-response operator choices.

To inform future aerogel manufacture, we investigated the different laboratory-scale aerogel fabrication technologies (rapid supercritical extraction (RSCE), CO2 supercritical extraction (CSCE), alcohol supercritical extraction (ASCE)). Our results from anticipatory LCA for laboratory-scaled aerogel fabrication demonstrated that RSCE method offers lower cumulative energy and ecotoxicity impacts compared to conventional aerogel fabrication methods (CSCE and ASCE).

The final objective of this study was to investigate different surface coating techniques to enhance oil recovery by modifying the existing aerogel surface chemistries to develop chemically responsive materials (switchable hydrophobicity in response to a CO2 stimulus). Our results showed that studied surface coating methods (drop casting, dip coating, and physical vapor deposition) were partially successful to modify surface with CO2 switchable chemical (tributylpentanamidine), likely because of the heterogeneous fiber structure of the aerogel blankets. A possible solution to these non-uniform coatings would be to include switchable chemical as a precursor during the gel preparation to chemically attach the switchable chemical to the pores of the aerogel.

Taken as a whole, the implications of this work are that mechanical deployment and recovery of aerogel composite blankets is a viable oil spill response strategy that can be deployed today. This will ultimately enable better oil uptake without the uptake of water, potential reuse of the collected oil, reduced material and energy burdens compared to competitive sorbents (e.g., PUF), and reduced occupational exposure to oiled sorbents. In addition, sorbent blankets and booms could be deployed in coastal and open-ocean settings, respectively, which was previously impossible.

Azobenzene disperse dyes are the fastest-growing category of commercial dyestuffs, accounting for 70% of the 9.9 million tons of industrial dye colorants used annually. Azobenzene disperse dyes are intended to be applied to synthetic fabrics such as polyester, nylon, and acrylic; however, azo dyes may also be used in cosmetic products such as hair dyes, and in fashion accessories such as leather goods. Recently, our group and others have detected azobenzene disperse dyes in dust particles collected from the indoor environment, and raising concerns about the release of these chemicals from products and human exposure. Although extensive literature characterizes these chemicals as toxic contaminants in aquatic environments, to date there exists little data on levels, exposures, and hazards associated wit exposures to azobenzene disperse dyes in the indoor environment. The presence of these dyes in the indoor environment is concerning. House dust is a sink for many contaminants that leach out or off-gas from products in the home. Due to children’s unique behaviors (e.g. crawling and hand to mouth activity) they have higher exposure to chemicals associated with dust. Azobenzene disperse dyes are implicated in literature as potentially allergenic: they are known to be present in clothing that elicits allergic reactions such as skin sensitization. Therefore, it is of crucial importance to support research that seeks to characterize children’s exposure in the home environment, and evaluate the in vitro effects of azobenzene disperse dyes. The hypothesis of this research dissertation is that azobenzene disperse dyes are prevalent in dust collected from the indoor environment at concentrations of concern for human health. In the first aim of this thesis research, azobenzene disperse dyes were characterized in commercial mixtures and in children’s polyester clothing. Azo dyes were first purified from dyestuffs by Soxhlet extraction and flash chromatography and then analyzed using ultra-high-performance liquid chromatography (UHPLC) coupled with high resolution mass spectrometry (HRMS), as well as by 1H and 13C NMR for structural elucidations. Nineteen total azobenzene dyes were detected in dyestuffs via a non-targeted analysis approach, including Disperse Blue 79:1, Disperse Blue 183:1, Disperse Orange 44, Disperse Orange 73, Disperse Red 50, Disperse Red 73, and Disperse Red 354. Samples of children's polyester clothing (n=X) were then analyzed via UHPLC-HRMS. In clothing, 21 azobenzene disperse dyes were detected, 12 of which were confirmed and quantified via reference standards. Individual dyes in apparel were quantified at concentrations up to 9230 μg dye/g shirt, with geometric means ranging 7.91–300 μg dye/g shirt. Total dye load in apparel was quantified at up to 11,430 μg dye/g shirt. This research supported the development of reference standards and library mass spectra for azobenzene disperse dyes previously absent from standard and spectral libraries. This study was the first to confirm and quantify these azo compounds in children’s products, facilitating a more robust understanding of sources of azobenzene disperse dyes in the indoor environment. The second aim of this thesis research investigated the presences and quantities of azobenzene disperse dyes and related compounds in indoor house dust (n=188) collected from homes in Durham, NC. Using a targeted approach, we quantified 12 azo disperse dyes and quantified at least one dye in every house dust sample. Detection frequencies ranged from 11% to 89%; of the dyes that were detected in at least 50% of the samples, geometric mean levels ranged from 32.4 to 360 ng/g. HRMS suspect screening analysis identified an additional eight azobenzene compounds in dust that are present at high relative abundances. This study indicates that azo disperse dyes and related compounds are ubiquitous in the indoor environment. To support quality assurance and control during the analysis, a house dust Standard Reference Material (NIST SRM 2585) was extracted and analyzed with the samples. Based on the detection and abundance of azo dyes in SRM 2585, which was prepared from hundreds of dust samples collected in the mid 1990s, azo dye levels in the indoor environment may be increasing over time. To our knowledge, this is the most comprehensive quantitative study of azo disperse dyes in house dust to date. Future studies are needed to quantify additional dyes in dust, particularly those identified here via suspect screening, and to examine exposure pathways of dyes in the indoor environment where children are concerned. The third aim of this thesis research examined the binding reactivity of azobenzene disperse dyes to nucleophilic peptide residues in order to understand their potential reactivity as electrophilic allergenic sensitizers. The Direct Peptide Reactivity Assay (DPRA) was utilized via both a spectrophotometric method and a high-performance liquid chromatography (HPLC) method. Dyes isolated from the commercial dyestuffs, and several potential transformation products, were tested. All dyes were found to react with nucleophilic peptides in a dose-dependent manner with pseudo-first order (kobserved) activity, but overall to react more potently with cysteine than with lysine: EC10 values for cysteine binding were determined as low as 0.005mM and pseudo-first order rate constants as high as 0.04 hr-1 (as observed for Disperse Blue 79:1). Observed rate constants were correlated to metrics of structural features such as Hammett constants and electrophilicity indices, indicating that binding reactivity may be related to structural properties of azobenzene disperse dyes. In addition to examining dyes, the reactivity of extracts of polyester shirts were also examined; shirt extracts with high relative abundances of azobenzene disperse dyes were observed to induce greater peptide reactivity. Results suggest that azobenzene disperse dyes may function as immune sensitizers, and that clothing containing azobenzene disperse dyes may pose risks for skin sensitization. Collectively, this thesis research suggests that azobenzene disperse dyes are common in clothing, and appear to be near ubiquitous in house dust. Given their reactivity in vitro, this may present health consequences, particularly for young children.

Commercial shipping activities place significant strain on one of our most important natural resources as demand for affordable global trade demands ever increasing marine traffic. It has long been recognized as one of the greatest threats to the health of the world’s oceans due to the translocation of invasive species by way of ballasting operations. However, the industry’s role in the global movement of anthropogenic compounds has not been previously investigated. Upcoming regulatory change will further add to the environmental burden as ships will be required to treat ballast water using disinfecting techniques, potentially generating toxic disinfection byproducts. This dissertation was thus focused on revealing current and future potential environmental impacts on the marine environment by using a combination of high resolution mass spectrometry instruments.

Ship ballast water and port water samples were analyzed using both targeted and non-targeted analyses to characterize the organic pollutant burden contained within tanks. This revealed the presence of contaminants derived from both land sources, such as agricultural runoff, as well as compounds associated with shipboard maintenance protocols. Several of these compounds are likely to serve as precursors for disinfection byproduct formation as the shipping industry begins to incorporate ballast water treatment systems. The role of natural organic matter in disinfection byproduct formation was then investigated by chlorinating natural and synthetic seawater. Using a combination of high resolution gas and liquid chromatography paired with accurate mass spectrometry, comprehensive disinfection byproduct profiles were generated to better understand environmental conditions responsible for their formation. A large amount of novel brominated compounds were tentatively identified and should be addressed further prior to global release during ballasting operations. Finally, the ability for continued disinfection byproduct formation to occur beyond quenching disinfection reactions was investigated. This is important to understand further potential risk to sensitive coastal ecosystems beyond the release of treated ballast water.

This dissertation used non-targeted workflows to supplement standard targeted analyses in order to discover compounds that may be of environmental concern relating to the shipping industry. As such, informed recommendations can be made as to the proper environmental conditions in which seawater chlorination should and should not be used. In addition, this allowed for discovery of additional novel disinfection byproducts which can be further investigated for toxicity potential.

Single-walled carbon nanotubes (SWNT) are highly ordered filamentous nanocarbon structures. As their commercial and industrial use becomes more widespread, it is anticipated that SWNT will enter the environment through waste streams and product degradation. Because of their highly hydrophobic nature, SWNT aggregate and settle out of aqueous environments, especially in saline environments such as estuaries. Therefore, sediments are a likely environmental sink for SWNT once released. It is important to understand how these materials will impact benthic estuarine systems since they are the probable target area for SWNT exposure in addition to containing many lower trophic level organisms whose survvial and contaminant body burdens can have a large impact on the overall ecosystem. Disruptions in lower trophic level organism survival can have negative consequences for higher trophic levels, impacting the overall health of the ecosystem. It is also important to consider contaminant bioaccumulation, trophic transfer and biomagnification. If SWNT are taken up by benthic invertebrates, there is the possibility for trophic transfer, increasing the exposure of SWNT to higher trophic level organisms that otherwise would not have been exposed. If this type of transfer occurs in environmentally important species, the potential for human exposure may increase. My research aims to determine the magnitude of the toxicity and bioaccumulation of SWNT in benthic estuarine systems, as well as determine how they interact with other contaminants in the environment. This research will contribute to the knowledge base necessary for performing environmental risk assessments by providing information on the effects of SWNT to benthic estuarine systems.

Before investigating the environmental effects of SWNT, it is imperative that a measurement method is established to detect and quantify SWNT once they enter the environment. This research utilized pristine, semiconducting SWNT to develop extraction and measurement methods to detect and quantify these specific materials in environmental media using near infrared fluorescence (NIRF) spectroscopy. Semiconducting SWNT fluoresce in the near infrared (NIR) spectrum when excited with visible&ndashNIR light. This unique optical property can be used to selectively measure SWNT in complex media.

The fate, bioavailability, bioaccumulation and toxicity of SWNT have not been extensively studied to date. Pristine SWNT are highly hydrophobic and have been shown to strongly associate with natural particulate matter in aquatic environments. In light of this, I have focused my research to examine the influence of sediment and food exposure routes on bioavailability, bioaccumulation, and toxicity of structurally diverse SWNT in several ecologically-important marine invertebrate species. No significant mortality was observed in any organism at concentrations up to 1000 mg/kg. Evidence of biouptake after ingestion was observed for pristine semiconducting SWNT using NIRF spectroscopy and for oxidized 14C&ndashSWNT using liquid scintillation counting. After a 24 hour depuration period, the pristine semiconducting SWNT were eliminated from organisms to below the method detection limit (5 &mug/mL), and the 14C&ndashSWNT body burden was decreased by an order of magnitude to a bioaccumulation factor (BAF) of <0.01. Neither pristine SWNT nor oxidized 14C&ndashSWNT caused environmentally relevant toxicity or bioaccumulation in benthic invertebrates. Overall, the SWNT were not bioavailable and appear to associate with the sediment.

In addition to investigating the toxicity and bioaccumulation of SWNT as an independent toxicant, it is important to consider how they will interact with other contaminants in the environment (i.e., increase or decrease toxicity and bioaccumulation of co&ndashcontaminants, alter the environmental transport of co&ndashcontaminants, induce degradation of co&ndashcontaminants, etc.). I wanted to investigate the effects of SWNT on a complex mixture of contaminants already present in a natural system. New Bedford Harbor (NBH) sediment, which is contaminated with polychlorinated biphenyls (PCBs), was amended with pristine SWNT to determine if the presence of SWNT would mitigate the toxicity and bioaccumulation of the PCBs in deposit-feeding invertebrates. A dilution series of the NBH sediment was created using uncontaminated Long Island Sound (LIS) sediment to test 25% NBH sediment, 50% NBH sediment, 75% NBH sediment, and 100% NBH sediment. The results of this work showed increased organism survival and decreased bioaccumulation of PCBs in treatments amended with SWNT, with the greatest reduction observed in the 25% NBH sediment treatment group amended with 10 mg SWNT/g dry sediment. Polyethylene (PE) passive samplers indicated a reduction of interstitial water (ITW) PCB concentration of greater than 90% in the 25% NBH sediment + 10 mg SWNT/g dry sediment amendment. The ITW concentration was reduced because PCBs were not desorbing from the SWNT. Lower bioavailability leads to reduced potential for toxic effects, supporting the observation of increased survival and decreased bioaccumulation. Once in the sediment, not only are SWNT not bioavailable, they act as a highly sorptive phase, such as black carbon (BC), into which hydrophobic organic contaminants (HOCs), such as PCBS and polycyclic aromatic hydrocarbons (PAHs), can partition, thereby reducing the toxicity and bioavailability of co-occurring HOCs.

To more fully understand the impact of SWNT in this environment, their biodegradability also needs to be investigated. Biodegradation of SWNT could lead to release and/or transformation of sorbed HOCs as well as a change in the inherent transport, toxicity, and bioaccumulation of SWNT in the estuarine environment. Because the persistence of SWNT will be a primary determinant of the fate of these materials in the environment, I conducted experiments to determine if the fungus Trametes versicolor, the natural bacterial communities present in NBH sediment, and municipal wastewater treatment plant sludge could degrade or mineralize oxidized 14C&ndashSWNT. Over a six month time period, no significant degradation or mineralization was observed. In all treatments, approximately 99% of the 14C-SWNT remained associated with the solid phase, with only approximately 0.8% of added 14C present as dissolved species and only 0.1% present as 14CO₂. These small pools of non-SWNT 14C were likely due to trace impurities, as no differences in production were observed between treatments and abiotic (killed) controls.

Single-walled carbon nanotubes (SWCNT) are unique, anthropogenic allotropes of nanoparticulate black carbon. As numerous industrial and commercial uses of SWCNT result the heavy expansion of production of this material, the release of SWCNT is likely to occur, increasing their level in air, water and soil. SWCNTs have been shown to cause adverse impact in organisms from direct exposure through ingestion or inhalation. In addition to direct exposure, SWCNT can also induce toxicity to organisms by indirect exposure such as adsorption of hydrophobic contaminants (HOCs). One unique property of SWCNT is the quantized nature of their electronic structure, which is dependent on the chiral wrapping angle of the sp2 hybridized graphene sheet that comprises the wall of each SWNT species. Using probe HOCs – one planar polycyclic aromatic hydrocarbon (PAH)14 C-naphthalene and one halogenated aromatic 14 C-hexachlorobenzene and purified conductive and semiconductive SWCNT species, my first study aimed at assessing the role of SWCNT electronic structure on HOC sorption. Despite their differences in electronic structures, the results indicated that overall the electronic structure does not influence the adsorption of HOCs. However, due to the large specific surface area, SWCNT have a general high affinity for HOCs. Upon release of SWCNT into aquatic environment, SWCNT have the potential to affect the distribution of organic contaminants by acting as strong sorbent.

A significant barrier to studying toxicity of SWCNT to animal models is the lack of in vivo techniques to track and quantify SWCNT for assessing their distribution, transport and bioaccumulation. The fluorescence resulting from the unique band gap of each species of semiconductive SWCNT allows the detection and quantification of a bulky SWCNT sample using near infrared fluorescence spectroscopy (NIRF). NIRF is highly sensitive to detect SWCNT in biological tissues due to the low fluorescence in the near infrared region from biological samples. Two exposure routes were investigated using NIRF: ingestion from dietary track using fathead minnow (FHM) fish model in an aquatic environment and inhalation through lung using mouse model. The SWCNT extraction conditions were optimized and validated using spike recovery experiments. SWCNT were extracted from fish tissues, intestine, and liver using ultrasonic extraction in 2% sodium deoxycholate1extraction. Proteinase K digestion was needed for dissolving mouse lung prior to SDC extraction. The quantification results showed that while SWCNT readily passed through fish dietary track with minimal partition into the lumen tissue and caused no acute toxicity; SWCNT was less mobile in respiratory system and was responsible for the lung-term pulmonary disease induced.

The fate, transport and bioaccumulation of SWCNT are essential information for risk assessment and making environmental regulations for nanomaterials. Currently the lack of standardized sensitive characterization and quantitative analytical methods for SWCNT determination at the current levels in the environment is one major barrier for evaluation of their real impact to the environment. NIRF is sensitive for environmental samples. However, this technique is not sensitive to all types of SWCNT. Metal catalysts are widely used in synthetic production of SWCNTs, leading to total metal content ranging from 5 - 30%. The metal: metal ratios and metal: carbon ratios of SWCNT are very distinctive from many geological materials. A metal fingerprinting approach was developed by monitoring the metal type and metal: metal ratios, along with elemental carbon content. SWCNT can be principally quantified using inductive coupled plasma mass spectrometry (ICP-MS). Metal content, metal: metal ratios, elemental carbon and metal: carbon ratios were analyzed for two aerosol matrices, the urban dust NIST SRM 1649b and aerosol collected at Duke University using three types of SWCNT: SG65 SWCNT, SG65i SWCNT and P2 SWCNT. Results demonstrated that the metal finger approach worked well with all aerosol matrices with detection limits near ng m-3. It worked best with elements that were less abundant in the background such as Co and Y. This method offers a robust and economic approach for application to occupational spaces for monitoring possible SWCNT release.

Applying a similar approach in sediment presents a significant challenge as background metals present in sediment complicates such analyses. To overcome these challenges, we have applied density gradient ultracentrifuge (DGU) to isolate and separate SWCNT in sediment extracts prior to both NIRF and ICP-MS analysis. Several types of SWCNTs (arc discharge, CoMoCat, and HiPCO) were spiked and subsequently extracted from estuarine sediments. SWCNTs were separated into different bands after DGU, primarily into two distinct horizons (one showed near infrared fluorescence, while the other did not). Two techniques,near-infrared spectroscopy (NIRF) and ICP-MS, were applied for quantitation of SWCNTs in these bands. Results indicate excellent separation of SWCNT from interferences in sediments. We have also discovered an apparent disconnect between the metal catalyst particles and SWCNT during density gradient ultracentrifuge separation. It is clear that the SWCNT (within the NIRF band) is not physically associated with metal catalyst. This result was further confirmed using single-particle ICP-MS. Although DGU separation seems to be an outstanding method for isolating SWCNT from aquatic sediment for analysis, our current findings indicate that metal fingerprints derived from residual catalyst may not be a good tracer for SWCNT occurrence and fate in marine sediments, as the associated metal catalyst particles in SWCNT preparations might be transported in different ways relative to the SWCNT.

Overall, my research explored several analytical techniques to detect and quantify SWCNTs at their relevant concentration in various environmental matrices. These techniques will provide essential information for evaluating the environmental impact based on SWCNTs fate, transport and bioaccumulation in the environment.

Over 7 million liters of Corexit® series dispersants were applied in the Gulf of Mexico during the 2010 Deepwater Horizon oil spill to facilitate the dispersion of crude oil into the water column. At the time of application, the composition, fate, and transformation kinetics of the surfactants in Corexit®9500 were relatively unknown. Recent advances in high-resolution mass spectrometry, such as resolving power, mass accuracy, and acquisition rates, have allowed for comprehensive characterization of complex surfactant mixtures in environmental matrices. The objective of this dissertation was to develop a method for comprehensive characterization of Corexit in the marine environment using high-resolution mass spectrometry. Specifically, I assessed the kinetic and biodegradation rates and transformation products of Corexit®9500 in under environmentally relevant conditions.

In Chapter 2, I identified individual nonionic polysorbate surfactants in Corexit using ultra high-resolution mass spectrometry. The method allowed for greater confident in structural assignment and systematic differentiation of isobaric and isomeric compounds. I examined the heterogeneity of Corexit based on differences in the hydrophilic core and hydrophobic tail groups. Specifically, the nonionic surfactants exhibited variability in the degree of esterification, fatty acid chain length and saturation as well as different core groups and ethoxymer distribution. The composition of Corexit has implications on the utility, fate, and persistence during an oil spill emergency response.

In Chapter 3, I investigated Corexit degradation under biotic and abiotic conditions using temperate seawater collected from the Pivers Island Coastal Observatory in Beaufort, NC. Corexit degraded under both biotic and abiotic conditions, although biodegradation rates were two to four times faster. Kinetic degradation rates were highly dependent on the degree of esterification and fatty acid chain length. However, they were not dependent on the core group, fatty acid saturation, or degree of ethoxylation. The only observed transformation products were the nonesterified ethoxylates generated by ester hydrolysis. Abiotic hydrolysis rates were also dependent on temperature. Increased temperature had a greater influence on the monoester surfactants degradation rates than surfactants that contained two or more ester moieties. I determined the kinetic degradation rates for individual surfactants, ethoxymer series, and ester components and compared degradation rates to polysorbate mixtures.

In Chapter 4, I examined the impact of crude oil on Corexit partitioning and degradation in Arctic seawater collected from the Chuckchi Sea. Components of Corexit did not partition into the crude oil layer based on surfactant hydrophobicity. Instead, the total abundance of Corexit increased in the water column in the presence of dispersed oil. The transformation products detected were the nonesterified ethoxylates, which suggested ester hydrolysis was the main pathways of degradation. The biodegradation rates of the ester components were slightly faster with dispersed oil due to the greater concentrations in the water column. In addition, observed abiotic hydrolysis rates at cold temperatures agreed with estimated rates calculated from the kinetic variable determined in Chapter 3. Overall, Corexit followed the same degradation pathway with slower transformation kinetics in Artic seawater in the presence and absence of crude oil.

Finally, Chapter 5 presented results from the microbial community analysis in the Corexit only and Corexit dispersed crude oil treatments. In the presence of Corexit, Bacteroidetes dominated the microbial community within 24-hours. Bacteroidetes were also present of dispersed oil and untreated water, however, in lower abundance. We did not observe a dramatic change in the microbial structure after the monoester component of Corexit was removed after 24-hours. The communities maintained a large degree of diversity in the presence of Corexit and dispersed crude oil, however after 5 days Proteobacteria (specifically Oceanospirillales and Altermonadales) and Flavobacterilia accounted for 75% of the community in the Corexit treatment. The inclusion of both dispersant and oil had significant effects on microbial community structure, which can be correlated to the degradation of dispersants.

High resolution mass spectrometry analysis allowed me to perform a complete characterization of Corexit and its related polysorbates, as well as determine the degradation rates and identify transformation products under various environmental conditions. I detected individual ethoxymers and evaluated the heterogeneity of the mixtures as well as the kinetic rates of degradation. I showed that the components of Corexit degrade on varying time scales based on structural similarities. All nonionic components of Corexit were removed within 10 days in temperate seawater and after 20 days in Arctic seawater. These studies are among the most comprehensive analysis of nonionic polysorbate surfactants under environmental conditions and will help to profile other dispersants and inform the application of Corexit series dispersants in future oil spill disasters.

Human activities represent a significant burden on the global water cycle, with large and increasing demands placed on limited water resources by manufacturing, energy production and domestic water use. In addition to changing the quantity of available water resources, human activities lead to changes in water quality by introducing a large and often poorly-characterized array of chemical pollutants, which may negatively impact biodiversity in aquatic ecosystems, leading to impairment of valuable ecosystem functions and services. Domestic and industrial wastewaters represent a significant source of pollution to the aquatic environment due to inadequate or incomplete removal of chemicals introduced into waters by human activities. Currently, incomplete chemical characterization of treated wastewaters limits comprehensive risk assessment of this ubiquitous impact to water. In particular, a significant fraction of the organic chemical composition of treated industrial and domestic wastewaters remains uncharacterized at the molecular level. Efforts aimed at reducing the impacts of water pollution on aquatic ecosystems critically require knowledge of the composition of wastewaters to develop interventions capable of protecting our precious natural water resources.

The goal of this dissertation was to develop a robust, extensible and high-throughput framework for the comprehensive characterization of organic micropollutants in wastewaters by high-resolution accurate-mass mass spectrometry. High-resolution mass spectrometry provides the most powerful analytical technique available for assessing the occurrence and fate of organic pollutants in the water cycle. However, significant limitations in data processing, analysis and interpretation have limited this technique in achieving comprehensive characterization of organic pollutants occurring in natural and built environments. My work aimed to address these challenges by development of automated workflows for the structural characterization of organic pollutants in wastewater and wastewater impacted environments by high-resolution mass spectrometry, and to apply these methods in combination with novel data handling routines to conduct detailed fate studies of wastewater-derived organic micropollutants in the aquatic environment.

In Chapter 2, chemoinformatic tools were implemented along with novel non-targeted mass spectrometric analytical methods to characterize, map, and explore an environmentally-relevant “chemical space” in municipal wastewater. This was accomplished by characterizing the molecular composition of known wastewater-derived organic pollutants and substances that are prioritized as potential wastewater contaminants, using these databases to evaluate the pollutant-likeness of structures postulated for unknown organic compounds that I detected in wastewater extracts using high-resolution mass spectrometry approaches. Results showed that application of multiple computational mass spectrometric tools to structural elucidation of unknown organic pollutants arising in wastewaters improved the efficiency and veracity of screening approaches based on high-resolution mass spectrometry. Furthermore, structural similarity searching was essential for prioritizing substances sharing structural features with known organic pollutants or industrial and consumer chemicals that could enter the environment through use or disposal.

I then applied this comprehensive methodological and computational non-targeted analysis workflow to micropollutant fate analysis in domestic wastewaters (Chapter 3), surface waters impacted by water reuse activities (Chapter 4) and effluents of wastewater treatment facilities receiving wastewater from oil and gas extraction activities (Chapter 5). In Chapter 3, I showed that application of chemometric tools aided in the prioritization of non-targeted compounds arising at various stages of conventional wastewater treatment by partitioning high dimensional data into rational chemical categories based on knowledge of organic chemical fate processes, resulting in the classification of organic micropollutants based on their occurrence and/or removal during treatment. Similarly, in Chapter 4, high-resolution sampling and broad-spectrum targeted and non-targeted chemical analysis were applied to assess the occurrence and fate of organic micropollutants in a water reuse application, wherein reclaimed wastewater was applied for irrigation of turf grass. Results showed that organic micropollutant composition of surface waters receiving runoff from wastewater irrigated areas appeared to be minimally impacted by wastewater-derived organic micropollutants. Finally, Chapter 5 presents results of the comprehensive organic chemical composition of oil and gas wastewaters treated for surface water discharge. Concurrent analysis of effluent samples by complementary, broad-spectrum analytical techniques, revealed that low-levels of hydrophobic organic contaminants, but elevated concentrations of polymeric surfactants, which may effect the fate and analysis of contaminants of concern in oil and gas wastewaters.

Taken together, my work represents significant progress in the characterization of polar organic chemical pollutants associated with wastewater-impacted environments by high-resolution mass spectrometry. Application of these comprehensive methods to examine micropollutant fate processes in wastewater treatment systems, water reuse environments, and water applications in oil/gas exploration yielded new insights into the factors that influence transport, transformation, and persistence of organic micropollutants in these systems across an unprecedented breadth of chemical space.

Plastic, while incredibly useful to both industrial and commercial products due to its flexibility and durability, has created a global waste management issue. In 2020, roughly 368 million tons of plastic was produced for packaging, textiles, consumer products, transportation, construction, electronics and more. Due to the lack of a circular economy for plastic, a large majority will be used once before being taken to landfills, incinerators, and recycling facilities. A fraction of this waste is also mismanaged and disposed of in the environment. Plastic debris in the environment is found within freshwater lakes, rivers, and streams where sedimentation can occur or transport to the marine environment. Plastic waste in aqueous environments has the potential to undergo abiotic and biotic weathering that will cause fragmentation to the polymer result in the release of microplastics and potentially hazardous polymer associated chemicals. Polymer associated chemicals (PACs) include polymer additives and monomers that are intentionally incorporated into the polymer to imbue the material with certain properties along with non-intentionally added substances like processing impurities. Some PACs have previously demonstrated toxicity including being mutagenic, carcinogenic, and estrogenic. PACs are not physically bound to the polymer and can be released into aqueous environments. Thus, plastic pollution introduces a risk of harm to marine and freshwater organisms via ingestion of microplastics that will result in exposure to potentially hazardous chemicals. The objective of this dissertation aims to further characterize the risk of polymer associated chemicals released into aqueous environments by answering these three questions: (1) What is the leaching behavior of PACs within various simulated aqueous environments? (2) How are PACs chemically transformed in simulated aqueous environments? (3) To what extent do released PACs and mixtures of PACs contribute to the estrogenic activity in a polymer leachate? In chapter 2, I studied the influence of carbon nanotube loading and various abiotic factors on the release of the monomers bisphenol A (BPA) and 4-tert-buylphenol (TBP) from epoxy and polycarbonate nanocomposites submerged in simulated freshwater environments. Single walled carbon nanotube (SWCNT) loading within the polymer nanocomposites (PNCs) demonstrated a decrease in monomeric concentrations released into water. Temperature, pH, UV light, and polymer size were found to be the most significant factors influencing release of TBP and BPA from PNCs. Additionally, the relative leaching behavior demonstrated differences by polymer type and chemical over the 5-day leaching experiments. These results provided important data to assess the risk posed by SWCNT polymer composites as they age in the environment. In chapter 3, I examined the release and fate of PACs from polypropylene (PP) and polyurethane (PU) microplastics during 12-month freshwater wetland mesocosm experiments and 3-month freshwater laboratory photolysis and leaching studies. Liquid chromatography coupled to high-resolution mass spectrometry (HRMS) is a powerful analytical technique used to characterize soluble organic pollutants in complex aqueous matrices. I utilized the data acquired from our HRMS with a non-targeted mass spectrometry workflow to identify novel polymer additives (Tinuvin 770), monomers (4-(4-formamidobenzyl)phenyl) formamide), and non-intentionally added substances (ricinine). Additionally, I was able to use this information to structurally annotate abiotically driven transformation products of two PACs. Leaching behavior of PACs quantified in both studies varied significantly where mesocosm PAC concentrations decreased over 12 months and laboratory-controlled PAC concentrations increased over 3 months. Further, UV pretreatment to the microplastics highlighted the difference in PACs that were UV labile or photo transformed. This work demonstrated the importance of utilizing both laboratory and mesocosm based studies in analyzing the fate and occurrence of PACs released from microplastics into freshwater environments. In chapter 4, four polymers (latex (LX), polyethylene (PE), polypropylene (PP), and polystyrene (PS)) were submerged in simulated freshwater, seawater, fish gastric fluid, seabird gastric fluid and solvent extracts to characterize leachable and potentially endocrine disrupting PACs. Suspect screening and targeted analysis were employed to quantify known PACs and structurally annotate PACs. In vitro bioassays were utilized to determine estrogenic responses of individual chemicals and chemically representative mixtures of the seabird digestate. Suspect screening characterized 20 polymer associated chemicals in the PE shopping bag, PS foam and PP string functioning as catalysts, antioxidants, lubricants, colorant intermediates, and surfactants. Additionally, in silico fragmentation workflows were employed to structurally annotate unknown sulfurous containing polymer associated chemicals released from PS foam samples. Of the four compounds quantified in the leachates, Tris(2,4-di-tert-butylphenyl) phosphate demonstrated significant estrogenic response at relevant concentrations found within the samples. Further, chemical mixtures of previously quantified phenols and phthalates explained 20% of the estrogenic activity within the PE shopping bag seabird digest samples. The implications of this work highlight the necessity of coupling non-targeted screening tools to in vitro assays for predicting the risk of polymer associated chemicals in the environment. In summary, this dissertation coupled targeted and non-targeted mass spectrometry workflows to characterize the broad diversity of leachable PACs. This work additionally highlighted the importance of analyzing environmental PAC transformations to understand the fate of PACs in water. Further, toxicity studies combined with identification of potentially hazardous chemicals further characterized the risk of endocrine disruption from PACs released into simulated marine stomachs. Taken together, my work represents significant progress in characterizing the behavior and risk of polymer associated chemicals in aqueous environments.