Kinetic model framework for aerosol and cloud surface chemistry and gas-particle interactions – Part 2: Exemplary practical applications and numerical simulations

Abstract

Abstract.A kinetic model framework with consistent and unambiguous terminology and universally applicable rate equations and parameters for aerosol and cloud surface chemistry and gas-particle interactions has been presented in the preceding companion paper by Pöschl, Rudich and Ammann (Pöschl et al., 2007), abbreviated PRA. It allows to describe mass transport and chemical reaction at the gasparticle interface and to link aerosol and cloud surface processes with gas phase and particle bulk processes. Here we present multiple exemplary model systems and calculations illustrating how the general mass balance and rate equations of the PRA framework can be easily reduced to compact sets of equations which enable a mechanistic description of time and concentration dependencies of trace gas uptake and particle composition in systems with one or more chemical components and physicochemical processes.Time-dependent model scenarios show the effects of reversible adsorption, surface-bulk transport, and chemical aging on the temporal evolution of trace gas uptake by solid particles and solubility saturation of liquid particles. They demonstrate how the transformation of particles and the variation of trace gas accommodation and uptake coefficients by orders of magnitude over time scales of microseconds to days can be explained and predicted from the initial composition and basic kinetic parameters of model systems by iterative calculations using standard spreadsheet programs. Moreover, they show how apparently inconsistent experimental data sets obtained with different techniques and on different time scales can be efficiently linked and mechanistically explained by application of consistent model formalisms and terminologies within the PRA framework.Correspondence to: M. Ammann (markus.ammann@psi.ch) Steady-state model scenarios illustrate characteristic effects of gas phase composition and basic kinetic parameters on the rates of mass transport and chemical reactions. They demonstrate how adsorption and surface saturation effects can explain non-linear gas phase concentration dependencies of surface and bulk accommodation coefficients, uptake coefficients, and bulk solubilities (deviations from Henry's law). Such effects are expected to play an important role in many real atmospheric aerosol and cloud systems involving a wide range of organic and inorganic components of concentrated aqueous and organic solution droplets, ice crystals, and other crystalline or amorphous solid particles.

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VI – heterogeneous reactions with liquid substrates

“…Approximate formulas for C diff or diff have been derived in the literature (Brown, 1978;Fuchs and Sutugin, 1970;Pöschl et al, 2007;Seinfeld and Pandis, 1998) for various geometries, such as suspended aerosol particles, but also for cylindrical flow tubes. They are a function of the geometry (e.g., particle diameter, d p ) and the diffusion coefficient of X, D g , and γ .…”

“…A quasi steady state resistance model has frequently been used to describe the uptake of gas species to surfaces, and to relate the experimentally observable net probability of uptake (γ , see below) to fundamental physical parameters. In this model, a linear combination of flux resistances (decoupled and normalized fluxes) by analogy to resistances in electric circuits, is used to describe the uptake process Jayne et al, 1990;Pöschl et al, 2007), and we will refer to these formulations below where appropriate. Models involving solution of coupled differential rate equations of mass transport and chemical reactions using continuum flow formulations and gas kinetic formulations (Behr et al, 2004;Flückiger and Rossi, 2003;Pöschl et al, 2007;Pfrang et al, 2010;Shiraiwa et al, 2009Shiraiwa et al, , 2010 have recently been described and circumvent steady state approximations that are not easy to assess.…”

Technical note: Monte Carlo genetic algorithm (MCGA) for model analysis of multiphase chemical kinetics to determine transport and reaction rate coefficients using multiple experimental data sets

“…The essential parameters we use to describe an atmospheric multiphase chemical kinetic system of reactive trace gases X and bulk material Y include chemical reaction rate coefficients at the surface (k SLR ) and in the bulk (k BR ) of aerosol particles; bulk diffusion coefficients of reactive trace gases (D b,X ) and the bulk matrix (D b,Y ); accommodation coefficients (α s,X ) and desorption lifetimes (τ d,X ) of trace gases to the particle surface to determine transient and equilibrium adsorption behaviour; and equilibrium constants for the solubility of reactive trace gases (K sol,cc,X ), typically expressed in terms of Henry's law coefficients (H cp,X ) Ammann and Pöschl, 2007;Shiraiwa et al, 2010;Berkemeier et al, 2013). In its first application the MCGA was used to fit individual data sets of the decay of oleic acid upon ozonolysis (Berkemeier et al, 2013), highlighting the need for fitting to multiple experimental data sets to constrain kinetic parameters.…”

Shikimic acid ozonolysis kinetics of the transition from liquid aqueous solution to highly viscous glass

“…46 Such a self-reaction has been suggested to govern the long-term O 3 uptake to soot. 47 In the absence of surface sensitive analysis tools, the nature of the species involved in detail remains speculative. At low RH, when the overall uptake is low, such a reaction could significantly contribute to the total O 3 loss to shikimic acid in our case.…”