Compositional Evolution of Secondary Organic Aerosol as Temperature and Relative Humidity Cycle in Atmospherically Relevant Ranges

Abstract

Atmospheric secondary organic aerosols (SOA) play an important role in the global particulate matter budget, and their chemical compositions determine critical properties that impact radiative forcing and human health. During temporal and spatial transport, atmospheric particles undergo ambient temperature and relative humidity (RH) changes or cycles that may transform their chemical compositions. Here, we report compositional evolution of SOA from α-pinene ozonolysis in a smog chamber as the temperature and RH cycle within atmospherically relevant ranges (5−35°C; 10−80% RH). The results suggest that the organic vapor condensation is limited during cooling, in contrast to volatility-based predictions, likely due to high viscosity of the α-pinene SOA particles and the potential enrichment of semivolatile products in the particle surface region. Combining a number of online and offline aerosol bulk and molecular-level measurements, we determine that particle-phase reactions occur reversibly and irreversibly throughout the temperature/RH cycles, substantially modifying concentrations of the SOA constituents and forming new products. Further, the presence of water is found to enhance the SOA O/C ratios prominently during cooling (high RH). These findings have important implications for understanding the chemical evolution of SOA in the atmosphere through their lifetime and long-range transport.

The Aarhus Chamber Campaign on Highly Oxygenated Organic Molecules and Aerosols (ACCHA): particle formation, organic acids, and dimer esters from <i>α</i>-pinene ozonolysis at different temperatures

“…A number of smog chamber studies have investigated the effect of α-pinene concentration and reaction temperature on the formation of SOA from α-pinene oxidation (Svendby et al, 2008;Pathak et al, 2007;Tillmann et al, 2010;Warren et al, 2009;Kourtchev et al, 2016;Kristensen et al, 2017;Zhao et al, 2019a). Most of published studies, however, focus on SOA mass yield (defined as mass of SOA formed per mass of reacted VOC) and report higher yields with increasing VOC concentrations and lower temperatures.…”

Structural Characterisation of Dimeric Esters in α-Pinene Secondary Organic Aerosol Using N2 and CO2 Ion Mobility Mass Spectrometry

“…This technique is increasingly used in the structural characterisation of small molecules since the introduction of the first commercial IMS-TOFMS in 2006 [9]. In the field of atmospheric science, IMS-TOFMS is successfully used for the molecular characterisation of β-pinene originating organosulfates [10], isoprene originating organosulfates [11], aerosol bound alkyl nitrates [12], classification of atmospherically relevant organic compounds [13], aqueous phase oligomerisation of α,β-unsaturated carbonyls and acids [14], separation of highly oxygenated molecules in laboratory-generated α-pinene SOA [15], particle-phase reaction products of α-pinene oxidation [16], and heterogeneous oxidation of organic aerosols [17,18].…”

Temperature effects on optical properties and chemical composition of secondary organic aerosol derived from <i>n</i>-dodecane

“…Therefore, it is important to study SOA formation and optical properties under varying atmospheric conditions to simulate the processes in the real atmosphere. There have been a number of smog chamber experiments on the effect of seed particles (Huang et al, 2017;Denjean et al, 2014;Song et al, 2013;Lee et al, 2013;Li et al, 2017aLi et al, , 2018Trainic et al, 2011); oxidant type, e.g., NO 3 (Peng et al, 2018;Lu et al, 2011;OH, Liu et al, 2015;Lin et al, 2015;Li et al, 2014;Nakayama et al, 2013;Cappa et al, 2011) and O 3 (Peng et al, 2018;Kim et al, 2014;Flores et al, 2014;Kim and Paulson, 2013); oxidation concentrations, e.g., photochemical age (Zhong and Jang, 2014;Kim et al, 2014;Lambe et al, 2012Lambe et al, , 2013; and relative humidity (RH;Titos et al, 2016;McNeill, 2015;Denjean et al, 2015;Li et al, 2017b;Sareen et al, 2017;Ye et al, 2016;Michel Flores et al, 2012) on SOA formation and the RI values of SOA derived from both biogenic and anthropogenic volatile organic compounds (VOCs). There have also been many studies investigating temperature effects on SOA formation and composition (Takekawa et al, 2003;Svendby et al, 2008;Clark et al, 2016;Lamkaddam et al, 2016;Huang et al, 2018;Mu et al, 2018;Zhao et al, 2019;…”