The Role of Desorption Lifetime and Adsorption Energies in Multiphase Chemical Kinetics
Abstract
Representing multiphase chemical kinetics on a molecular level remains challenging due to the large compositional variety of airborne particulate matter and gas species, in addition to the wide temperature and humidity range present in the atmosphere. The underlying molecular processes are important for a scientific understanding and reliable description of gas uptake and chemical evolution of organic aerosol including the partitioning of gas species to and from the particle. In addition, multiphase oxidation reactions can impact the particles' ability to act as cloud condensation and ice nuclei. Adsorption of gas species at the surface of a liquid or solid material, either as physisorption or chemisorption, represents commonly the first step of multiphase chemical reactions. The desorption rate and lifetime (DL) can be derived from knowledge of the desorption energy for given adsorbate and substrate. Desorption is convoluted with elementary reactive and non-reactive processes including uptake, adsorption, ozonolysis, and gas-particle partitioning. At lower temperatures, the DL can increase significantly, counteract slow rates of chemical reaction and diffusion, and potentially enhance the overall gas uptake which can involve reversible, reactive, and catalytic processes operating in parallel or sequentially on the surface or in the bulk of the particles. Accurate DL lifetime estimates yield a better constraint of such reactive and non-reactive processes, important when interpreting experimental and modeling studies. We present an evaluation and compilation of desorption energies of atmospherically relevant gas species and substrates to demonstrate the importance of the desorption process for the derivation of uptake kinetics by liquid and solid substrates. Sensitivity simulations of reactive and non-reactive uptake using kinetic flux models are conducted to demonstrate the impact of DL and temperature on the overall multiphase chemical kinetics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A51C..07K
- Keywords:
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- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE