Influence of seed aerosol surface area and oxidation rate on vapor wall deposition and SOA mass yields: a case study with <i>α</i>-pinene ozonolysis

Abstract

Abstract. Laboratory chambers, invaluable in atmospheric chemistry and aerosol formation studies, are subject to particle and vapor wall deposition, processes that need to be accounted for in order to accurately determine secondary organic aerosol (SOA) mass yields. Although particle wall deposition is reasonably well understood and usually accounted for, vapor wall deposition is less so. The effects of vapor wall deposition on SOA mass yields in chamber experiments can be constrained experimentally by increasing the seed aerosol surface area to promote the preferential condensation of SOA-forming vapors onto seed aerosol. Here, we study the influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis. The observations are analyzed using a coupled vapor–particle dynamics model to interpret the roles of gas–particle partitioning (quasi-equilibrium vs. kinetically limited SOA growth) and α-pinene oxidation rate in influencing vapor wall deposition. We find that the SOA growth rate and mass yields are independent of seed surface area within the range of seed surface area concentrations used in this study. This behavior arises when the condensation of SOA-forming vapors is dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O3 concentrations for the same initial α-pinene concentration. When the α-pinene oxidation rate increases relative to vapor wall deposition, rapidly produced SOA-forming oxidation products condense more readily onto seed aerosol particles, resulting in higher SOA mass yields. Our results indicate that the extent to which vapor wall deposition affects SOA mass yields depends on the particular volatility organic compound system and can be mitigated through the use of excess oxidant concentrations.

Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region

“…These ELVOCs have been observed during both chamber and in situ measurements in Germany (Mutzel et al, 2015). Several studies showed the importance of nighttime SOA formation from MT via nitrate radical oxidation, resulting in the formation of organic nitrates (Pye et al, 2015;Bean and Ruiz, 2016;Xu et al, 2015;Nah et al, 2016). Pye et al (2010) showed the importance of reactive nitrogen and pointed out the fact that organic nitrate accounts for more than a half of the monoterpene oxidation products in the particle phase over the US.…”

“…Organic nitrates are formed where biogenic VOCs and anthropogenic NO x sources interact (Pye et al, 2015;Xu et al, 2015;Bean and Ruiz, 2016;Nah et al, 2016). We used here the parameterisation of Pye et al (2015) to account for the formation of organic nitrate compounds from the oxidation by OH and NO 3 of MT.…”

“…01, 0.0141, 0.0199, 0.0281, 0.0398, 0.0562, 0.0794, 0.1121, 0.1585, 0.2512, 0.3981, 0.6310, 1.0, 1.2589, 1.5849, 1.9953, 2.5119, 3.5481, 5.0119, 7.0795 and 10.0 µm. The condensation/evaporation of inorganic aerosols is determined using the thermodynamic model ISORROPIA (Nenes et al, 1998) with a bulk equilibrium approach in order to compute partitioning between the gaseous and condensed phases of particles.…”

The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

“…Experimental measurements of SOA formation in laboratory Teflon chambers are influenced by deposition of both particles and vapors to the chamber walls, and evaluation of the SOA yield from VOC oxidation must take careful accounting for such wall losses (e.g., Zhang et al, 2014;Nah et al, 2017Nah et al, , 2016. We seek to assess the extent to which both vapor and particle deposition onto the entrance region and quartz wall of the flow tube is influential in flow tube reactor studies.…”

Semivolatile POA and parameterized total combustion SOA in CMAQv5.2: impacts on source strength and partitioning

“…Second, it is likely that previous estimates of SOA yields from wellknown VOC precursors (e.g., toluene, xylene, alkanes, isoprene, terpenes) derived from smog chamber experiments were biased by unaccounted loss of semivolatile organic vapors to the chamber walls (Hildebrandt et al, 2009;Mat-B. N. Murphy et al: Comprehensive evaluation of CMAQ semivolatile POA sunaga and Ziemann, 2010; Loza et al, 2010;Yeh and Ziemann, 2014;Zhang et al, 2014Zhang et al, , 2015Cappa et al, 2016;Nah et al, 2016;Krechmer et al, 2016;Saha and Grieshop, 2016;Ma et al, 2017;Nah et al, 2017). The magnitude of this bias likely varies substantially among experimental systems (i.e., precursor and oxidant identity) and experimental conditions (e.g., seed concentration, relative humidity, temperature; Krechmer et al, 2016;Nah et al, 2016).…”