Atmospheric Aerosols as Chemical Micro Reactors in the Environment
Abstract
The objective of the proposed study is to study the fundamental surface photo-reactivity of organic environmentally relevant classes of compounds, and investigate how these reactive surface species interact with the gaseous and bulk aqueous phases. Specifically, the multiphase surface photochemistry of aldehyde and ketones producing reactive organic radicals will be investigated to establish their ability to react with fatty acids, fatty alcohols and gas phase reactants themselves not able to absorb solar terrestrial radiation. The light initiated chemistry will be compared with OH radical reaction to evaluate photochemistry as a source of secondary organic aerosol precursors in the natural and built environment. The proposed investigation addresses the basic science aspects of sunlight-initiated, water-mediated chemistry of organic molecules when several phases are present and interact. The methods to be employed consist of a combination of laboratory, simulation chamber and modeling studies. The expected results will lead to new mechanisms, dynamics and rates of photochemical reactions occurring on aerosol surfaces important in the environment. What distinguishes this work from other efforts is the emphasis on deriving molecular level mechanisms and quantitative models for atmospheric organic photochemistry in the unique environment at water surfaces whose treatment in current models is a Òweak linkÓ requiring significant attention. Results expected from the proposed study has the potential to improve the performance of models by incorporating a fundamentally correct treatment of chemistry affecting organic aerosols with implications to managing their role in visibility and health effects. Over the temperature and pressure range in the EarthÕs atmosphere, water in all its phase has an important role in mediating chemistry. Atmospheric particles formed by condensation of water with salts, minerals and organic compounds provide interesting and poorly understood microreactors, important in determining the EarthÕs temperature, and visibility in the clean and polluted environment. Given the large reactive surface area of indoor and outdoor aerosol particles, the sea surface microlayer and the surface of fogs and cloud droplets, chemistry in these environments has been suggested to explain field and laboratory results. The significance of the proposed work is to provide fundamental studies of chemistry at water surfaces, especially light initiated organic chemistry in these environments, information not currently available precluding their inclusion in atmospheric models and evaluation of their health effects. Epidemiological observations implicate aerosols in air pollution in indoor and outdoor environments. Aerosol optical and chemical properties as well as their health effects depend on the particle mass, composition, size and surface area. Organic compounds emitted from natural and man made sources interact with sunlight in and on aerosols affecting nucleation, growth, optical and properties of these particles as well as their surroundings. Chemical processing on aerosols lead to pollution, deleterious health effects and reduced visibility. The proposed work involves interdisciplinary collaboration between the fields of chemistry, environmental science, experiment and modeling, providing far-reaching opportunities for education. The significance of the proposed study to education is to bring interdisciplinary ideas from chemistry and environmental science to the development of young scientists and to non-scientific audiences.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 06, 2018
- Source ID
- W911NF1710115
Entities
People
- Veronica Vaida
Organizations
- Army Contracting Command
- United States Army
- University of Colorado Boulder