Volatility Change during Droplet Evaporation of Pyruvic Acid

Abstract

Atmospheric water-soluble organic gases such as pyruvic acid are produced in large quantities by 13 photochemical oxidation of biogenic and anthropogenic emissions and undergo water-mediated 14 reactions in aerosols and hydrometeors. These reactions can contribute to aerosol mass by forming 15 less volatile compounds. While progress is being made in understanding the relevant aqueous 16 chemistry, little is known about the chemistry that takes place during droplet evaporation. Here we 17 examine the evaporation of aqueous pyruvic acid droplets using both the Vibrating Orifice Aerosol 18 Generator (VOAG) and an electrodynamic balance (EDB). In some cases pyruvic acid was first 19 oxidized by OH radicals. The evaporation behavior of oxidized mixtures was consistent with 20 expectations based on known volatilities of reaction products. However, independent VOAG and 21 EDB evaporation experiments conducted without oxidation also resulted in stable residual 22 particles; the estimated volume yield was 10-30% of the initial pyruvic acid. Yields varied with 23 temperature and pyruvic acid concentration across cloud, fog, and aerosol-relevant concentrations. 24The formation of low volatility products, likely cyclic dimers, suggests that pyruvic acid accretion 25 reactions occurring during droplet evaporation could contribute to the gas-to-particle conversion 26 of carbonyls in the atmosphere. 27 mass. [4][5][6] However, the contribution of aqueous reactions to SOA mass remains uncertain due in 35 part to a limited understanding of precursors and limited laboratory results to parameterize 36 models. 1,[7][8][9][10][11] Quantifying the impacts of aqueous and multiphase chemistry on aerosol mass 37 remains challenging, and a more detailed understanding of product volatility is needed.A significant fraction of low molecular weight acids, aldehydes and carbonyls dissolve into 39 cloud or fog droplets. In the absence of additional reactions, these WSOGs largely evaporate 40 during water evaporation; the trace amounts that remain in the aerosol phase are determined by 41 their partial pressure in the gas phase and activity in the aerosol matrix. However, multiphase 42 reactions can generate low-volatility products that are retained in the equilibrated aerosol. Several 43 important criteria determine whether aqueous processing can appreciably increase SOA mass: (1) 44 the precursor must be abundant, (2) it must have a high vapor pressure before aqueous reactions, 45(3) it must have a high Henry's law coefficient and thus strongly partition into water, and (4) it 46 must react in the aqueous phase to form less volatile products. 47

Evolution of volatility and composition in sesquiterpene-mixed and α-pinene secondary organic aerosol particles during isothermal evaporation

“…Comparable evaporation rates under intermediate and high RH conditions suggest that particle evaporation can be approximated as a liquid-like process for both conditions (i.e., at RH ≥ 40%), in agreement with previous observations of α-pinene SOA particle evaporation (Yli-Juuti et al, 2017;Buchholz et al, 2019;. Additionally, particulate water content may also induce aqueous-phase processes during isothermal evaporation (Buchholz et al, 2019;Petters et al, 2020 SOA particles, we observed strong evidence of such processes under high RH conditions (RH = 80%), which indicates the presence of aerosol-water-induced chemistry (see section 3.3.3).…”

“…Although increasing evidence from laboratory and field observations have suggested the importance of aqueous-phase processes, such reactions are still underrepresented in the existing models because of a lack of fundamental knowledge (McNeill, 2015). While the aqueous-phase processes of simple, typically small carbonyl compounds have been well studied so far (De Haan et al, 2009;Schwier et al, 2010;Yasmeen et al, 2010;Zhao et al, 2012;Zhao et al, 2013;Petters et al, 2020), more studies should investigate the processes involving complex and large molecules with multiple functional groups. To investigate the changes in volatility of SOA particles, we need to compare the number of ions at each desorption temperature between fresh (0.25 h, ℎ ( )) and RTC (4.25 h, ( )) samples collected by on the FIGAERO filter.…”

Pre-deliquescent water uptake in deposited nanoparticles observed with in situ ambient pressure X-ray photoelectron spectroscopy

“…Uptake of glyoxal has been shown to be enhanced at acidic interfaces (Shi et al, 2020). Changes in droplet size via evaporation or condensation can affect the chemical reactions that take place at the surface via changes in the relative dimensions and chemical environments of the interface and associated bulk phases (Prisle et al, 2012;Djikaev and Ruckenstein, 2019;Petters et al, 2020). The presence of surface-active organic molecules on droplet surfaces can also affect droplet surface tension (Shulman et al, 1996;Prisle et al, 2010b;Bzdek et al, 2020) and morphology (Kwamena et al, 2010) that affect both warm (Sareen et al, 2013;Ovadnevaite et al, 2017) and ice cloud nucleation (Knopf and Forrester, 2011;Perkins et al, 2020) as well as droplet coalescence (Pak et al, 2020).…”

Evolution of volatility and composition in sesquiterpene-mixed and <i>α</i>-pinene secondary organic aerosol particles during isothermal evaporation

“…Particulate water reduces the viscosity and thus enhances particle evaporation with increasing RH. The comparable evaporation rates under intermediate-and high-RH conditions suggest that particle evaporation can be approximated as a liquid-like process for both conditions (i.e., at RH ≥ 40 %), but in addition to this plasticizing effect, particulate water content may also induce aqueous-phase processes during isothermal evaporation (Buchholz et al, 2019;Petters et al, 2020). For the investigated SOA particles, we observed strong evidence of such processes under high-RH conditions (RH = 80 %).…”

“…Although increasing evidence from laboratory and field observations have suggested the importance of aqueous-phase processes, such reactions are still underrepresented in the existing models because of a lack of fundamental knowledge (Mc-Neill, 2015). While the aqueous-phase processes of simple, typically small carbonyl compounds have been well studied so far (De Haan et al, 2009;Schwier et al, 2010;Yasmeen et al, 2010;Li et al, 2011;Zhao et al, 2012Zhao et al, , 2013Petters et al, 2020), more studies should investigate the processes involving complex and large molecules with multiple functional groups.…”