Chemical ageing and transformation of diffusivity in semi-solid multi-component organic aerosol particles

Abstract

Recent experimental evidence underlines the importance of reduced diffusivity in amorphous semi-solid or glassy atmospheric aerosols. This paper investigates the impact of diffusivity on the ageing of multi-component reactive organic particles approximating atmospheric cooking aerosols. We apply and extend the recently developed KM-SUB model in a study of a 12-component mixture containing oleic and palmitoleic acids. We demonstrate that changes in the diffusivity may explain the evolution of chemical loss rates in ageing semi-solid particles, and we resolve surface and bulk processes under transient reaction conditions considering diffusivities altered by oligomerisation. This new model treatment allows prediction of the ageing of mixed organic multi-component aerosols over atmospherically relevant timescales and conditions. We illustrate the impact of changing diffusivity on the chemical half-life of reactive components in semi-solid particles, and we demonstrate how solidification and crust formation at the particle surface can affect the chemical transformation of organic aerosols

Oxidation of a model alkane aerosol by OH radical: the emergent nature of reactive uptake

“…1,62 Eq. 7 cannot be connected to microscopic events such as sticking of gases to the particle or subsequent free radical chain reactions that consume the aerosol material.…”

Development of an inorganic and organic aerosol model (CHIMERE 2017<i>β</i> v1.0): seasonal and spatial evaluation over Europe

“…-Some recent experimental studies emphasize the need to account for dynamical aspects of the organic aerosol formation rather than assuming thermodynamic equilibrium with the gas phase because organic aerosols can be highly viscous (Virtanen et al, 2010;Cappa and Wilson, 2011;Pfrang et al, 2011;Shiraiwa et al, 2011;Vaden et al, 2011;Shiraiwa and Seinfeld, 2012;Abramson et al, 2013). To our knowledge, this phenomenon was never investigated inside a 3-D air quality model.…”

Gas–particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology

“…55,56 Oligomerization leads to the formation of low volatility compounds, which can enhance solidification and crust formation at the particle surface, potentially affecting reaction pathways and kinetics. 57 …”