Glassy aerosols with a range of compositions nucleate ice heterogeneously at cirrus temperatures

Abstract

Abstract. Atmospheric secondary organic aerosol (SOA) is likely to exist in a semi-solid or glassy state, particularly at low temperatures and humidities. Previously, it has been shown that glassy aqueous citric acid aerosol is able to nucleate ice heterogeneously under conditions relevant to cirrus in the tropical tropopause layer (TTL). In this study we test if glassy aerosol distributions with a range of chemical compositions heterogeneously nucleate ice under cirrus conditions. Three single component aqueous solution aerosols (raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA) and levoglucosan) and one multi component aqueous solution aerosol (raffinose mixed with five dicarboxylic acids and ammonium sulphate) were studied in both the liquid and glassy states at a large cloud simulation chamber. The investigated organic compounds have similar functionality to oxidised organic material found in atmospheric aerosol and have estimated temperature/humidity induced glass transition thresholds that fall within the range predicted for atmospheric SOA. A small fraction of aerosol particles of all compositions were found to nucleate ice heterogeneously in the deposition mode at temperatures relevant to the TTL (< 200 K). Raffinose and HMMA, which form glasses at higher temperatures, nucleated ice heterogeneously at temperatures as high as 214.6 and 218.5 K respectively. We present the calculated ice active surface site density, n s , of the aerosols tested here and also of glassy citric acid aerosol as a function of relative humidity with respect to ice (RH i ). We also propose a parameterisation which can be used to estimate heterogeneous ice nucleation by glassy aerosol for use in cirrus cloud models up to ∼ 220 K. Finally, we show that heterogeneous nucleation by glassy aerosol may compete with ice nucleation on mineral dust particles in midlatitudes cirrus.

Quantifying water diffusion in high-viscosity and glassy aqueous solutions using a Raman isotope tracer method

“…Highly viscous aerosol particles have been found to act as heterogeneous IN and may play an important role in cirrus cloud formation (Murray et al, 2010b;Wagner et al, 2012;Wilson et al, 2012;Wang et al, 2012;Baustian et al, 2013). Heterogeneous nucleation of ice on glassy aerosol particles well below water saturation may lead to less, but larger, ice crystals which have a greater sedimentation velocity; this may be particularly important in the very cold and dry topical tropopause region where clouds play a key role in water transport into the stratosphere (Murray et al, 2010b).…”

Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities

“…Simulations show that total SOM mass concentrations can be overestimated or underestimated depending on what diffusion rates are used (Shiraiwa and Seinfeld, 2012). Chemical aging of atmospheric particles by heterogeneous reactions can depend on diffusion rates within SOM Kuwata and Martin, 2012;Zhou et al, 2013;Steimer et al, 2014;Houle et al, 2015) and heterogeneous ice nucleation may be influenced by the viscosity of SOM particles (Murray et al, 2010;Wang et al, 2012;Ladino et al, 2014;Schill et al, 2014;Wilson et al, 2012). Moreover, long-range transport of polycyclic aromatic hydrocarbons can depend on diffusion rates in a particle Zhou et al, 2013) and the efflorescence of crystalline salts can be hindered for highly viscous SOM (Murray, 2008;Murray and Bertram, 2008;Bodsworth et al, 2010;Song et al, 2013).…”

The efficiency of secondary organic aerosol particles acting as ice-nucleating particles under mixed-phase cloud conditions

“…The findings of the above-mentioned studies can be summarized as follows: Wang et al (2012) and Ignatius et al (2016) found that atmospheric SOA particles are potentially important for ice nucleation due to their semi-solid or solid phase states by investigating SOA from naphthalene and α-pinene, respectively, whereas Ladino et al (2014) and Wagner et al (2017) found that α-pinene SOA at first is an inefficient INP at cirrus temperatures, but after precooling of the SOA particles, ice nucleation ability is increased. Schill et al (2014) found that semi-solid or glassy SOA from aqueous processing of methylglyoxal with methylamine is a poor depositional INP; however, Wilson et al (2012) found other aqueous glassy aerosol to nucleate ice heterogeneously at temperatures relevant for cirrus formation in the tropical tropopause layer. All these studies investigated the ice-forming abilities of the SOA particles at temperatures in the cirrus regime (i.e.…”

“…Ice nucleation has been tested e.g. in expansion chambers (Murray et al, 2010;Wilson et al, 2012;Wagner et al, 2017), in continuous-flow diffusion chambers and flow tubes (Ladino et al, 2014;Ignatius et al, 2016), and in microscope systems (Wang et al, 2012;Baustian et al, 2013). Whether these formation pathways and ice nucleation initiation methods have an impact on the ice nucleation ability of the SOA particles is not clear.…”

“…The procedures for generation of the SOA particles as well as the methods of initiating ice nucleation do vary substantially among these experiments. For example, SOA formation has been initiated by dark ozonolysis (Prenni et al, 2009;Wagner et al, 2017) or photochemical reactions (Ladino et al, 2014;Ignatius et al, 2016), using gas-phase reactions (Wang et al, 2012;Ignatius et al, 2016) or aqueous processing (Wilson et al, 2012;Baustian et al, 2013;Schill et al, 2014). Ice nucleation has been tested e.g.…”