MOLECULAR CHARACTERIZATION OF FREE TROPOSPHERIC ORGANIC AEROSOL AND THE DEVELOPMENT OF COMPUTATIONAL TOOLS FOR MOLECULAR FORMULA ASSIGNMENT
MOLECULAR CHARACTERIZATION OF FREE TROPOSPHERIC ORGANIC AEROSOL AND THE DEVELOPMENT OF COMPUTATIONAL TOOLS FOR MOLECULAR FORMULA ASSIGNMENT

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Published: 2019

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Abstract : Organic aerosol affects human health and climate. These effects are largely determined by the composition of the organic aerosol, which is a complex mixture of species. Understanding the complexity of organic aerosol is critical to determining its effect on human health and climate. In this study, long range transported organic aerosol collected at the Pico Mountain Observatory was analyzed using ultrahigh resolution mass spectrometry. Organic aerosol transported in the free troposphere had an overall lower extent of oxidation than aerosol transported in the boundary layer. It was hypothesized that the lower oxidation was related to a more viscous phase state of the aerosol during transport. The results suggest that biomass burning organic aerosol injected into the free troposphere are more persistent than organic aerosol in the boundary layer. A sample was also analyzed using tandem FT-ICR MS/MS fragmentation, providing information about the functional group composition in the aerosol sample. This was done using a segmented scan approach, which revealed an unprecedented molecular complexity of unfragmented precursor ions. In addition to the expected CO2 and H2O neutral losses, neutral losses corresponding to carbonyl functional groups (C2H4O, CO) were observed. The abundance of carbonyl functional groups suggests a slower rate of aging in the atmosphere. Analysis of nitrogen and sulfur containing neutral losses highlighted a surprising abundance of reduced nitrogen and sulfur loss (NH3 and SH2). This further supports the hypothesis of slower aging in the free troposphere. Additional research was done to develop an R software package (MFAssignR) to perform molecular formula assignment with improved decision-making transparency, noise estimation, isotope identification, and mass recalibration. MFAssignR was found to assign the same molecular formula as other molecular formula assignment methods for the majority (97-99%) of mass peaks that were assigned a molecular formula by the compared methods. Additionally, MFAssignR was more effective at assigning molecular formulas to low intensity peaks relative to the other methods tested, leading to more overall molecular formula assignments. MFAssignR is available via GitHub and is the first open source package to contain a full pipeline of functions for data preparation and analysis for ultrahigh resolution mass spectrometry.

Molecular Characterization of Organic Aerosol by Mass Spectrometry
Molecular Characterization of Organic Aerosol by Mass Spectrometry

Author: Yuqian Gao

Publisher:

Published: 2011

Total Pages:

ISBN-13: 9781124611839

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Organic aerosol is a major constituent of atmospheric fine particles, especially over continental regions. These particles adversely affect human health and global climate. A significant fraction of organic aerosol is considered to be from the oxidation products of ozone and volatile organic compounds, which are called secondary organic aerosol (SOA). To study the formation mechanisms of secondary organic aerosol, it is important to characterize their molecular composition. The composition of secondary organic aerosol is very complex including thousands of species with molecular weight up to over a thousand Dalton. Methods utilized for the identification of these oxidation products involve advanced mass spectrometry techniques. In this dissertation, three mass spectrometry techniques were developed to study the molecular composition of organic aerosol. Firstly, online nano-aerosol sample deposition methods for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was developed to incorporate matrix particles directly with analyte particles onto a conventional MALDI plate. Secondly, a microsampling and analysis technique was developed in order to collect microgram samples and analyze them with high performance mass spectrometry. With this technique, the molecular composition of particle phase SOA at a low mass loading can be elucidated, which provides information about SOA formation at the early stages. A species with the (neutral molecule) formula C 17 H 26 O 8 (MW 358) increased substantially in intensity relative to other products as the mass loading decreased. Tandem mass spectrometry (MS n) of this species showed it to be a dimer of C 9 H 14 O 4 and C 8 H 12 O 4, most likely pinic acid and terpenylic acid, respectively. This species is likely to be critical at the early stages of SOA formation. Thirdly, ambient secondary electrospray ionization (ESI) source was designed to characterize the molecular composition of both gas and particle phases SOA online. This ion source was demonstrated to be applicable to a wide range of mass spectrometers having an ambient inlet. This technique provides a tool to acquire detailed information about possible SOA nucleation agents. A species with the (neutral molecule) formula C 20 H 36 O 6 (MW 372) was found in the gas-phase products of SOA, which could be critical for the new particle formation of SOA. Tandem mass spectrometry (MS n) of this species showed it to be a dimer of an organic hydroperoxide C 10 H 18 O 3, which is likely formed via OH-initiated oxidation pathway.

A Molecular Characterization of Biogenic Secondary Organic Aerosol by High-resolution Time-of-flight Mass Spectrometry
A Molecular Characterization of Biogenic Secondary Organic Aerosol by High-resolution Time-of-flight Mass Spectrometry

Author: Felipe Daniel Lopez-Hilfiker

Publisher:

Published: 2015

Total Pages: 178

ISBN-13:

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The guiding question to this research is: To what extent and by what mechanisms do biogenic volatile organic compounds contribute to atmospheric aerosol mass? To address this question we need to understand the chemistry that produces condensable vapors which when in the presence of particles may partition onto the aerosol surface depending on their chemical and physical properties. I developed an insitu gas and aerosol sampling system, the FIGAERO (Filter Inlet for Gases and AEROsol) to speciate gas and particle phase organics derived from photochemical reactions with biogenic volatile organic compounds under both field and laboratory conditions. By coupling the FIGAERO to a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-TOF-CIMS) I am able to elucidate chemical pathways by identifying elemental compositions and in some cases functional groups present in the detected molecular ions. The coupling of the FIGAERO to the HR-TOF-CIMS also allows the estimation of effective vapor pressures of the aerosol components and this information can be used to improve vapor pressure models and test associated partitioning theories and parameterizations. The approach also provides hundreds of speciated chemical tracers that can be correlated with traditional environmental and chemical measurements (e.g AMS, NOx, SO2, SMPS, VOC) to help derive sources and sinks and to constrain the mechanisms responsible for the formation and growth of organic aerosol. Measurements obtained across a wide range of conditions and locations allowing connections and contrasts between different chemical systems, providing insights into generally controlling factors of secondary organic aerosol (SOA) and its properties.

Molecular Characterization of Atmospheric Organic Matter in Biogenic Secondary Organic Aerosol, Ambient Aerosol and Clouds
Molecular Characterization of Atmospheric Organic Matter in Biogenic Secondary Organic Aerosol, Ambient Aerosol and Clouds

Author: Yunzhu Zhao

Publisher:

Published: 2014

Total Pages: 256

ISBN-13:

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Atmospheric aerosol affects the Earth's energy budget, reduces visibility and influences human health. The organic composition of aerosol is quite complex and continuously evolves through various atmospheric processes. To gain a deeper understanding of the molecular composition of atmospheric organic matter (AOM), chamber-generated biogenic secondary organic aerosol (SOA), ambient aerosol and cloud water samples were studied. Ultrahigh resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry was used to provide detailed molecular characterization of the atmospheric samples. Due to the extremely high mass resolution and mass accuracy, thousands of individual molecular formulas were identified in all of the samples studied. Multivariate statistical analysis methods were evaluated to compare the similarities and differences of the sample compositions. The biogenic SOA from three individual monoterpene precursors and a sesquiterpene precursor have clusters of peaks in their mass spectra, indicating that high molecular weight oligomers are a major component of the SOA. The monoterpene SOA have similar molecular compositions, which are different from the sesquiterpene SOA composition. The indicator species of SOA were identified using multivariate statistical analysis. Daily 24-hour water-soluble organic carbon samples from ambient aerosol collected at the Storm Peak Laboratory (SPL) show similar bulk chemical properties regarding their average elemental ratios and double bond equivalents. Using multivariate statistical analysis, the site meteorological conditions were found to affect the aerosol molecular composition. Days with strong UV radiation and high temperature were found to contain large numbers of biogenic SOA molecular formulas. Days with high relative humidity and high sulfate ion concentrations were found to contain many sulfur-containing compounds, suggesting their aqueous phase formation. The collection of cloud samples at the SPL provided an opportunity to study aqueous processing of AOM. The cloud composition was affected by biomass burning and SOA. Comparisons of the sample compositions indicate biogenic SOA components are commonly observed in ambient aerosol and cloud samples collected at the SPL. Thus, the ambient samples were used to confirm the biogenic SOA indicator species identified in chamber-generated SOA. This study of the three types of atmospheric samples helps to understand the composition of AOM with respect to atmospheric processes.

EXTREME MOLECULAR DIVERSITY IN BIOMASS BURNING ATMOSPHERIC ORGANIC AEROSOL OBSERVED THROUGH ULTRAHIGH RESOLUTION MASS SPECTROMETRY
EXTREME MOLECULAR DIVERSITY IN BIOMASS BURNING ATMOSPHERIC ORGANIC AEROSOL OBSERVED THROUGH ULTRAHIGH RESOLUTION MASS SPECTROMETRY

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Published: 2019

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Abstract : Ambient atmospheric aerosol is ubiquitous in the atmosphere, originating from a variety of natural and man-made sources. These microscopic particles have profound impacts on the global climate system as well as human health. The organic fraction of atmospheric aerosol is an extremely complex mixture which is not yet fully characterized. These unknown organic aerosol species contribute to the uncertainty in the effect of aerosol on climate and uncertainty in overall ambient aerosol toxicity. Light absorbing organic aerosol can interact with incoming solar radiation and contribute to atmospheric heating; however, the source apportionment and overall fate of these absorbing organic aerosol species are not fully understood. The burning of woody and vegetative materials (biomass) is expected to be one source, while secondary chemical reactions in aqueous phase aerosol and liquid water droplets are another. In this work, we have analyzed ambient samples from the Po Valley (Italy) and Pacific Northwest (USA) influenced by biomass burning. Using ultrahigh resolution mass spectrometry and subsequent molecular formula assignment, we observe an extreme level of molecular complexity in atmospheric aerosol. We make several key observations regarding both biomass burning organic aerosol and aqueous phase processing based on the molecular details and the observed elemental trends in the assigned formulas. We estimate oxidation levels, heteroatom functionalization, aromatic character, volatility and glass transition temperature based on reliable molecular formula assignments. Overall, this work describes a level of complexity in organic aerosol much greater than previously indicated. We suspect that any one analytical technique is likely to miss certain aspects of this mixture, and that a variety of analytical methods must be employed to fully characterize and resolve the complex mixture in atmospheric organic aerosol.

Aerosols in Atmospheric Chemistry
Aerosols in Atmospheric Chemistry

Author: Yue Zhang

Publisher: American Chemical Society

Published: 2022-04-01

Total Pages: 176

ISBN-13: 0841299293

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The uncertainties in the aerosol effects on radiative forcing limit our knowledge of climate change, presenting us with an important research challenge. Aerosols in Atmospheric Chemistry introduces basic concepts about the characterization, formation, and impacts of ambient aerosol particles as an introduction to graduate students new to the field. Each chapter also provides an up-to-date synopsis of the latest knowledge of aerosol particles in atmospheric chemistry.

Atmospheric and Aerosol Chemistry
Atmospheric and Aerosol Chemistry

Author: V. Faye McNeill

Publisher: Springer

Published: 2014-07-08

Total Pages: 267

ISBN-13: 3642412157

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Christian George, Barbara D’Anna, Hartmut Herrmann, Christian Weller, Veronica Vaida, D. J. Donaldson, Thorsten Bartels-Rausch, Markus Ammann - Emerging Areas in Atmospheric Photochemistry. Lisa Whalley, Daniel Stone, Dwayne Heard - New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Neil M. Donahue, Allen L. Robinson, Erica R. Trump, Ilona Riipinen, Jesse H. Kroll - Volatility and Aging of Atmospheric Organic Aerosol. P. A. Ariya, G. Kos, R. Mortazavi, E. D. Hudson, V. Kanthasamy, N. Eltouny, J. Sun, C. Wilde - Bio-Organic Materials in the Atmosphere and Snow: Measurement and Characterization. V. Faye McNeill, Neha Sareen, Allison N. Schwier - Surface-Active Organics in Atmospheric Aerosols.

Atmospheric Multiphase Chemistry
Atmospheric Multiphase Chemistry

Author: Hajime Akimoto

Publisher: John Wiley & Sons

Published: 2020-03-27

Total Pages: 544

ISBN-13: 1119422396

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An important guide that highlights the multiphase chemical processes for students and professionals who want to learn more about aerosol chemistry Atmospheric Multiphase Reaction Chemistry provides the information and knowledge of multiphase chemical processes and offers a review of the fundamentals on gas-liquid equilibrium, gas phase reactions, bulk aqueous phase reactions, and gas-particle interface reactions related to formation of secondary aerosols. The authors—noted experts on the topic—also describe new particle formation, and cloud condensation nuclei activity. In addition, the text includes descriptions of field observations on secondary aerosols and PM2.5. Atmospheric aerosols play a critical role in air quality and climate change. There is growing evidence that the multiphase reactions involving heterogeneous reactions on the air-particle interface and the reactions in the bulk liquid phase of wet aerosol and cloud/fog droplets are important processes forming secondary aerosols in addition to gas-phase oxidation reactions to form low-volatile compounds. Comprehensive in scope, the book offers an understanding of the topic by providing a historical overview of secondary aerosols, the fundamentals of multiphase reactions, gas-phase reactions of volatile organic compounds, aqueous phase and air-particle interface reactions of organic compound. This important text: Provides knowledge on multiphase chemical processes for graduate students and research scientists Includes fundamentals on gas-liquid equilibrium, gas phase reactions, bulk aqueous phase reactions, and gas-particle interface reactions related to formation of secondary aerosols Covers in detail reaction chemistry of secondary organic aerosols Written for students and research scientists in atmospheric chemistry and aerosol science of environmental engineering, Atmospheric Multiphase Reaction Chemistry offers an essential guide to the fundamentals of multiphase chemical processes.

Chemical Composition and Photochemical Evolution of Limonene Secondary Organic Aerosol Studied Using High Resolution Electrospray Ionization Mass Spectrometry
Chemical Composition and Photochemical Evolution of Limonene Secondary Organic Aerosol Studied Using High Resolution Electrospray Ionization Mass Spectrometry

Author: Adam Patrick Bateman

Publisher:

Published: 2011

Total Pages: 189

ISBN-13: 9781124668659

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Organic aerosols comprise hundreds, if not thousands, of distinct chemical compounds. Traditional analytical techniques for analysis of chemical composition lack the ability to completely characterize complex mixtures such as organic aerosol. Until recently, the best available methods could only provide information on selected aerosol compounds, on selected groups of compounds, or on sample-averaged elemental ratios. Such experimental limitations posed significant barriers to understanding the detailed chemical composition of organic aerosols and its atmospheric evolution. The unique HR ESI-MS methods developed in this research are able to not only characterize the organic aerosols average elemental ratios, but also simultaneously obtain information about hundreds or even thousands of individual compounds in organic aerosols. One of the key achievements of this work was the development of new methods for classification of individual compounds in organic aerosols by their functional groups using reactive HR ESI-MS. This contribution made it possible to track organic aerosols throughout their atmospheric evolution via functional group composition and average elemental ratios while still retaining the chemical composition of each individual compound. Other important scientific advances described in this thesis include: complete characterization of the chemical composition of limonene SOA as a function of particle size and reaction time; adaptation of PILS (particle-into-liquid sampler) to the HR ESI-MS platform; chemical characterization of the water soluble component of several types of organic aerosols; the effects of photochemical aging on the water soluble component of limonene SOA through characterization of the optical properties coupled with chemical composition; and investigation of photochemistry of carbonyls in model SOA matrices. The research included in this dissertation reviews the development of unique aerosol characterization tools utilizing the facilities at UCI and the Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory. The research project answered important questions regarding organic aerosol formation, evolution, and chemical composition that impact the direct and indirect influences of aerosols on Earth's climate.

Environmental Chemistry of Aerosols
Environmental Chemistry of Aerosols

Author: Ian Colbeck

Publisher: John Wiley & Sons

Published: 2008-03-24

Total Pages: 276

ISBN-13: 1405139196

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Aerosol particles are ubiquitous in the Earth’s atmosphere and are central to many environmental issues such as climate change, stratospheric ozone depletion and air quality. In urban environments, aerosol particles can affect human health through their inhalation. Atmospheric aerosols originate from naturally occurring processes, such as volcanic emissions, sea spray and mineral dust emissions, or from anthropogenic activity such as industry and combustion processes. Aerosols present pathways for reactions, transport, and deposition that would not occur in the gas phase alone. Understanding the ways in which aerosols behave, evolve, and exert these effects requires knowledge of their formation and removal mechanism, transport processes, as well as their physical and chemical characteristics. Motivated by climate change and adverse health effects of traffic-related air pollution, aerosol research has intensified over the past couple of decades, and recent scientific advances offer an improved understanding of the mechanisms and factors controlling the chemistry of atmospheric aerosols. Environmental Chemistry of Aerosols brings together the current state of knowledge of aerosol chemistry, with chapters written by international leaders in the field. It will serve as an authoritative and practical reference for scientists studying the Earth’s atmosphere and as an educational and training resource for both postgraduate students and professional atmospheric scientists.