Contaminants like plastics, pharmaceuticals, illicit drugs, and personal care products enter the oceans directly or indirectly from land runoff, rivers, and atmospheric deposition. While known to accumulate at the ocean surface, the efficiency of transfer into sea spray aerosols (SSA) at the ocean-air interface and their atmospheric lifetime once airborne is relatively understudied. Photosensitizing materials found in marine dissolved organic matter may lead to enhanced photochemical removal of pollutants. A complete analysis of these pollutants' transfer and environmental fate is warranted to improve our collective understanding of the full impact of human activities on public and ecological health. Additionally, the full complexity of the natural coastal marine atmosphere remains poorly understood, compounding the difficulty in isolating and understanding the impacts of anthropogenically introduced materials. Secondary marine aerosol (SMA) formed from the oxidation and condensation of biogenically emitted gases drives marine cloud formation, which may serve as a natural buffer system for human-caused climate change. Deepening our understanding of these complex systems requires detailed characterization of the organic compounds that constitute polluted and natural marine aerosols.

Our findings identify SSA as an important vector for transporting several illicit drugs, personal care products, and plastic additive compounds from the ocean to the atmosphere. Quantifying selected contaminants in aerosol and water samples across multiple coastal sites in San Diego revealed a regional hotspot near the Tijuana River outflow, with the amount of pollutants transferred into SSA dependent on their ocean concentration and lipophilicity. This airborne pathway underscores the need for revised health assessments in polluted coastal regions due to the heightened exposure risk for coastal residents and visitors.

An investigation of the photo-induced degradation kinetics of the toxic sunscreen ingredient oxybenzone (BP3) in seawater and SSA mimics reveals rapid degradation in aerosols compared to bulk solutions. Despite this rapid degradation, the formation of toxic transformation products suggests sustained environmental and health risks. Investigations into pure, binary, and ternary mixtures of BP3, NaCl, and the photosensitizer 4-benzoyl benzoic acid using solar-simulated light isolated the effects of salt and photosensitization on BP3 degradation.

The first-ever measurements of SMA by extractive electrospray ionization mass spectrometry highlighted the importance of hydrocarbons such as isoprene and monoterpenes in producing organic aerosol mass, demonstrating how the organic character of SMA shifts throughout a phytoplankton bloom, and identified the role of phytoplankton and bacterial production sources of sulfur- and nitrogen-containing substituents.

This dissertation emphasizes the intricate interactions between pollutants, natural marine processes, and atmospheric dynamics. It contributes to a deeper understanding of the complex interplay between coastal contaminants and marine atmospheric chemistry, highlighting the urgent need for comprehensive environmental management strategies.

Organic nitrates, produced from the oxidation of biogenic volatile organic compounds (BVOC) in the presence of nitrogen oxides (NOx), have significant contributions to the global secondary organic aerosol (SOA) budget and slow the production of ozone by sequestering NOx. Monoterpenes, such as α-pinene, are important organic nitrate and SOA precursors and are the second largest contributor to non-methane BVOC mass next to isoprene. It has been observed in previous studies that α-pinene-derived hyrdroxy nitrates readily partition to the particle phase, introducing a potential sink for atmospheric NOx through reactions such as acid-catalyzed hydrolysis. However, the role of relative humidity and particle acidity in the mass accommodation and rate of uptake of hydroxy nitrates by aerosol are not well understood, introducing a knowledge gap in the fate of atmospheric NOx. In this experiment, an α-pinene hydroxy nitrate is synthesized and introduced to a potential mass aerosol oxidation flow reactor (PAM-OFR) with dry, zero air flowed through a temperature controlled glass tube to elucidate the uptake rates of α-pinene hydroxy nitrate in the presence of ammonium sulfate seed aerosol. α-pinene hydroxy nitrate uptake kinetics are determined via analysis of hydroxy nitrate concentrations in the gas phase using a high-resolution time-of-flight chemical ionization mass spectrometer (HR-TOF-CIMS). Our results will report on the uptake kinetics of this hydroxy nitrate as a function of relative humidity and seed particle acidity and may provide new insight into the timescales at which α-pinene derived organic nitrates partition to the particle phase, offering more detailed considerations for future modeling studies.

The direct and indirect interactions of aerosols with solar and terrestrial radiation represent the most significant uncertainty in our understanding of Earth’s climate. Marine aerosols, comprised of freshly emitted or nascent sea spray aerosols (SSA), aged SSA, and secondary marine aerosol (SMA), significantly impact the global radiative budget, cloud and fog formation, and visibility and air quality in coastal marine environments. Biological processes in seawater impact marine aerosol chemical and physical properties. An important but understudied property of marine aerosol is its phase state or viscosity. Viscosity significantly influences gas-to-particle partitioning, liquid and ice cloud nucleation rates, and heterogeneous reaction kinetics, which can affect aerosol chemical composition, wet deposition rates, size, and thus aerosol impacts on climate and air quality. This work investigates the influence of biological activity, particle size, and oxidative aging processes on marine aerosol's molecular composition and phase states. Empirical observations of particle phase state are made through online particle bounce/rebound measurements and offline with atomic force microscopy. Findings indicate nascent SSA particles exhibit increasingly viscous or solid-like characteristics with greater seawater phytoplankton activity and decreasing particle size. SSA aged by OH radical is more viscous than nascent SSA. Increasing organic carbon content and chemical species with higher molecular weights were enriched in SSA during elevated phytoplankton growth in seawater and smaller SSA. We attribute the higher molecular weight and more viscous organic components in SSA to the production of colloidal or gel-like SSA formed through the complexation of polyanionic organic components with divalent cations, specifically Ca2+. In polluted air with high concentrations of marine volatile organic compounds and oxidants equivalent to a week of chemical aging in the atmosphere, SSA becomes more viscous, attributed to the functionalization of particulate organic carbon. Further aging up to the equivalent of weeks in the atmosphere leads to less viscous phase states, attributed to the volatilization and, thus, decreasing molecular weight of the SSA organic carbon. These results have the potential for a better understanding of processes such as ice nucleation and airborne transport of chemical pollutants and toxins in SSA in coastal environments, which are strongly influenced by viscosity.

Plastics have become ubiquitous in the world’s oceans, and recent work indicates that they can transfer from the ocean to the atmosphere in sea spray aerosol (SSA). SSA is the largest contributor to annual aerosol mass load and is a significant source of plastic to the atmosphere. Plastic additives, including bisphenol-A (BPA), represent a sizable fraction of consumer plastics and have been measured consistently in air over both terrestrial and marine environments. However, the chemical lifetimes of BPA and mechanisms by which it degrades with respect to photochemical and heterogeneous oxidation processes in aerosols are unknown. The work in this dissertation utilized an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) to monitor changes in aerosol composition with high time resolution. In Chapter 3, the photosensitized and OH- initiated heterogeneous oxidation kinetics of BPA in the aerosol phase consisting of pure-component BPA and internal mixtures of BPA, NaCl, and dissolved photosensitizing organic matter are presented. OH-initiated degradation is enhanced in the presence of chloride, likely due to the enhanced mobility of BPA in the more liquid-like particle due to the hygroscopicity of NaCl increasing the liquid water content within the aerosol. In contrast, photosensitized reactions were limited in the presence of chloride, which was attributed to quenching of triplet state formation by dissolved Cl− in the less viscous aqueous aerosol mixtures. In Chapter 4, the composition changes in SSA during a phytoplankton bloom are determined, including the temporal variability and trends dependent on specific biological processes occurring in seawater. Through this study, it was also established that EESI-TOF sensitivity is critically dependent on the sample's relative humidity after adjusting for pressure variations at the inlet and normalization to the reagent ion. In Chapter 5, the photosensitized degradation of BPA at high and low pH is investigated. At pH 3 and pH 11, the photosensitized degradation of BPA is inhibited, and the potential causes are discussed. This dissertation highlights important heterogeneous and photosensitized reactions which BPA undergoes, as well as the role of particle viscosity. Ultimately, this work contributes to our understanding of the lifetimes of hazardous plastic pollutants in SSA with implications for pollutant transport and exposure risks in coastal marine environments.

Triclosan, an antimicrobial agent incorporated in personal care and consumer products, is used to prevent bacterial contamination and material biodegradation. However, various studies have shown that triclosan exhibits toxic effects to aquatic species, persists in the environment, and poses as an endocrine disruptor. Triclosan can be leached from untreated wastewater and wastewater treatment plant effluent into ocean surface water as a contaminant. Consequently, it can become aerosolized in sea spray aerosol (SSA) and undergo degradation in the atmosphere to produce potentially more toxic transformation products, such as dichlorodibenzo-p-dioxin and chlorophenols. To understand the lifetime of triclosan in the aerosol phase in SSA, this research focuses on quantifying the kinetics and degradation lifetimes of triclosan with respect to heterogeneous oxidation by hydroxyl radicals (OH) and photosensitization reactions involving chromophoric dissolved organic matter (CDOM) mixed with inorganic salts that coexist in SSA. A potential aerosol mass oxidation flow reactor (PAM-OFR), used to simulate aerosol aging, is coupled with an extractive electrospray ionization high-resolution time-of-flight mass spectrometer (EESI-HR-ToF-MS) to study triclosan degradation kinetics and its transformation products in the aerosol phase in near real time. Results indicate that the reactive uptake of OH by single-component triclosan aerosol proceeds with a diffusion-corrected uptake coefficient of 0.15 ± 0.04. In the presence of humic acid, a CDOM proxy, the OH reactive uptake coefficient decreased to 0.09 ± 0.04, suggesting that CDOM inhibits triclosan degradation in the presence of OH radicals. Furthermore, the addition of the inorganic salt, NaCl, to the triclosan system increased the effective uptake coefficient to 0.29 ± 0.08. 2,8 dichlorodibenzo-p-dioxin (2,8 DCDD), a toxic transformation product, was potentially detected by the EESI-HR-ToF-MS in the aerosol phase indicating photodegradation as the major degradation pathway of triclosan. The half-life of triclosan in the aerosol phase with respect to heterogeneous oxidation by OH is estimated to be 18.63 ± 4.53 days. This project aims to gain a better understanding of the effects of photodegradation and OH radical heterogeneous oxidation on the lifetime of triclosan in the aerosol phase, the influence of added photosensitizer and inorganic salt, and potentially the contribution of triclosan degradation to the formation of more toxic transformation products.