Effects of Acid-Catalyzed Heterogeneous/Multiphase Reactions on Atmospheric Aerosol Composition and the Fate of Organic Compounds
Abstract
Atmospheric aerosol particles are microscopic in size and are composed of a variety of materials such as soil dust, sea salt, soot, inorganic salts, and organic matter. These particles provide surface area and condensed organic and aqueous phases for adsorption and absorption of atmospheric inorganic and organic chemicals, as well as microenvironments for chemical transformations. Aerosol particles also affect air quality, visibility, the hydrologic cycle, climate, and human and environmental health. A large fraction of the particulate mass consists of organic matter, which is either emitted directly from combustion sources or is formed in the atmosphere when volatile organic compounds emitted from anthropogenic and natural sources are oxidized to form products that condense to particles as secondary organic aerosol (SOA). In spite of the importance of SOA as a contributor to particulate mass, and its effect on the transport and fate of atmospheric organic chemicals and numerous environmental phenomena, the chemical and physical processes by which it is formed and transformed are still poorly understood. The overall objective this project is to investigate the chemical reactions of organic compounds that occur on or in aerosol particles, which are catalyzed by the presence of acids. These reactions are known to occur, but are not represented in models used to predict atmospheric processes because of a current lack of understanding of important physical and chemical properties of aerosols and because these reactions have not been properly characterized under atmospheric conditions. In particular, in this project laboratory studies will be conducted to simulate the chemistry that occurs in atmospheric organic aerosol particles under well-controlled conditions, and then changes in chemical composition will be monitored using a variety of state-of-the-art chromatographic, spectroscopic, and mass spectrometry methods. Information will be obtained on the distribution of oxidized organic compounds between organic and aqueous aerosol phases, the availability of acids to catalyze the reactions, and the effects of particle composition on the rates of reactions and equilibrium concentrations of products of these reactions under atmospheric conditions. The extent to which the experimental results obtained here can be used to model the effects of these reactions on aerosol composition, the fate of organic reaction products, and aerosol formation in realistic, complex aerosol systems will also be determined. The qualitative and quantitative information gained from this study will be extremely valuable to scientists seeking to understand and develop models to predict the behavior and fate of gaseous and particulate organic chemicals in the atmosphere, and the extent to which gas-phase and acid-catalyzed particle reactions influence their lifetimes, fates, and role in the formation of aerosol particles. These models are widely used to investigate the formation and properties of organic aerosol particles, which influence air quality, visibility, human and ecosystem health, the hydrologic cycle, and regional and global climate.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 06, 2018
- Source ID
- W911NF1710607
Entities
People
- Paul J Ziemann
Organizations
- Army Contracting Command
- United States Army
- University of Colorado Boulder