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

摘要

A kinetic model framework with consistent and unambiguousterminology and universally applicable rate equations and parametersfor aerosol and cloud surface chemistry and gas-particleinteractions has been presented in the preceding companion paper byP?schl, Rudich and Ammann (P?schl et al., 2007), abbreviatedPRA. It allows to describe mass transport and chemical reaction atthe gas-particle interface and to link aerosol and cloud surfaceprocesses with gas phase and particle bulk processes. Here wepresent multiple exemplary model systems and calculationsillustrating how the general mass balance and rate equations of thePRA framework can be easily reduced to compact sets of equationswhich enable a mechanistic description of time and concentrationdependencies of trace gas uptake and particle composition in systemswith one or more chemical components and physicochemical processes.Time-dependent model scenarios show the effects of reversibleadsorption, surface-bulk transport, and chemical aging on thetemporal evolution of trace gas uptake by solid particles andsolubility saturation of liquid particles. They demonstrate how thetransformation of particles and the variation of trace gasaccommodation and uptake coefficients by orders of magnitude overtime scales of microseconds to days can be explained and predictedfrom the initial composition and basic kinetic parameters of modelsystems by iterative calculations using standard spreadsheetprograms. Moreover, they show how apparently inconsistentexperimental data sets obtained with different techniques and ondifferent time scales can be efficiently linked and mechanisticallyexplained by application of consistent model formalisms andterminologies within the PRA framework.Steady-state model scenarios illustrate characteristic effects ofgas phase composition and basic kinetic parameters on the rates ofmass transport and chemical reactions. They demonstrate howadsorption and surface saturation effects can explain non-linear gasphase concentration dependencies of surface and bulk accommodationcoefficients, uptake coefficients, and bulk solubilities (deviationsfrom Henry's law). Such effects are expected to play an importantrole in many real atmospheric aerosol and cloud systems involving awide range of organic and inorganic components of concentratedaqueous and organic solution droplets, ice crystals, and othercrystalline or amorphous solid particles.