Physical and Chemical Characterization of Aerosols from Cyanobacterial Harmful Algal Blooms and Engineered Nanomaterials
Creators: name: Shi, Jia
Publisher: name: My University
Year: 2023
Subjects: subject: Cyanobacterial Harmful Algal Blooms
subject: Cyanopeptides
subject: Silver Nanoparticles
subject: Optical Photothermal Infrared + Raman Spectroscopy
subject: Microcystins
subject: Chemistry
subject: Science

description: Particles in the nanoscale regime like engineered nanoparticles (NPs) and atmospheric aerosol display unique physicochemical characteristics that impact human health and the environment. NPs have been incorporated into many consumer products, but their uptake in humans is poorly understood. Similarly, small aerosol particles have adverse health effects when inhaled deep into the lungs. The impacts of NPs and aerosol are dictated by their physicochemical properties, but their complex chemical compositions are analytically challenging to study due to their small sizes. In this dissertation, bulk and single particle analysis techniques were applied to study the digestion of engineered NPs and the aerosolization of biological material from cyanobacterial harmful algal blooms (cHABs) in ambient and laboratory-controlled settings. Silver nanoparticles (AgNPs) have exhibited antimicrobial properties, which has led to their integration in consumer products. However, the health effects of consuming AgNPs are poorly understood, particularly after undergoing transformations in the gastrointestinal tract. This study used an in vitro multi-vessel dynamic digestion model to simulate the dissolution of AgNPs in the stomach, duodenum, and jejunum. The size distribution AgNPs was monitored in the different vessels throughout the digestion process using nanoparticle tracking analysis, and elemental composition characterization was conducted with transmission electron microscopy with energy dispersive x-ray spectroscopy. Results showed that AgNPs aggregated in the stomach under a fasted condition (pH = 2) and remained aggregated in the intestinal fluid. Under a fed condition (pH = 5), the smaller AgNP aggregates formed in the stomach were redispersed in the intestine. This study highlights how the pH of the stomach and the pH-neutralizing effects in the intestinal fluids influenced the final physicochemical properties of AgNPs after the digestion process. Particles emitted from freshwater systems, lake spray aerosol (LSA), during a cyanobacterial harmful algal bloom (cHAB) potentially pose respiratory health risks to humans since they can contain toxins and other bioactive compounds produced by the cyanobacteria. Liquid chromatography with tandem mass spectrometry was used to quantify microcystins (MCs) and anabaenopeptins (APs) in ambient aerosol samples. Results highlight that the concentration of aerosolized MCs can be driven by other factors besides meteorological, with higher concentrations of MCs detected near a spillway structure and aeration systems. In addition, the first reported detection of APs demonstrated that they could be more common and abundant in the atmosphere than MCs near a cHAB. These results underscore the potential exposure to toxic and bioactive cyanometabolites in communities surrounding and downwind of cHABs. Bioaerosol identification is essential for understanding their impacts on public health and climate. Novel vibrational microspectroscopy techniques are needed to overcome the limitations of Raman (fluorescence interference) and Fourier-transform infrared spectroscopy (spatial resolution). Herein, Optical-photothermal infrared + Raman spectroscopy (O-PTIR+Raman) was utilized to identify bioaerosols in laboratory-generated LSA and ambient samples using the amide I and II fingerprints. Higher fractions of bioaerosols were observed in supermicron particles than submicron particles across all laboratory and ambient samples. Additionally, the complementary PTIR and Raman spectra collected assisted in the characterization additional organic and inorganic particle types. These results show the capability of O-PTIR+Raman to address the analytical challenges with aerosol analysis through vibrational spectroscopy. This dissertation investigated NPs and atmospheric aerosol using various analytical techniques. The results provide insight into their complex physical and chemical properties, which can directly impact human health and the environment.