Abstract
Abstract. Organic aerosols are measured at a remote site (Ersa) on the cape of Corsica in the northwestern Mediterranean basin during the winter campaign of 2014 of the CHemistry and AeRosols Mediterranean EXperiment (CharMEx), when high organic concentrations from anthropogenic origins are observed. This work aims to represent the observed organic aerosol concentrations and properties (oxidation state) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Because intermediate and semi-volatile organic compounds (I/S-VOCs) are the main precursors of SOAs at Ersa during winter 2014, different parameterizations to represent the emission and aging of I/S-VOCs were implemented in the chemistry-transport model of Polyphemus (different volatility distribution emissions and single-step oxidation vs multi-step oxidation within a volatility basis set – VBS – framework, inclusion of non-traditional volatile organic compounds – NTVOCs). Simulations using the different parameterizations are compared to each other and to the measurements (concentration and oxidation state). The highly observed organic concentrations are well reproduced in all the parameterizations. They are slightly underestimated in most parameterizations. The volatility distribution at emissions influences the concentrations more strongly than the choice of the parameterization that may be used for aging (single-step oxidation vs multi-step oxidation), stressing the importance of an accurate characterization of emissions. Assuming the volatility distribution of sectors other than residential heating to be the same as residential heating may lead to a strong underestimation of organic concentrations. The observed organic oxidation and oxygenation states are strongly underestimated in all simulations, even when multigenerational aging of I/S-VOCs from all sectors is modeled. This suggests that uncertainties in the emissions and aging of I/S-VOC emissions remain to be elucidated, with a potential role of formation of organic nitrate and low-volatility highly oxygenated organic molecules.
Highlights
Organic aerosols (OAs) are one of the main compound of submicron particulate matter (PM1; Jimenez et al, 2009)
Organic species that compose POAs are often classified depending on their volatility: intermediate volatility organic compounds (IVOCs; with saturation concentration C∗ in the range 103–106 μg m−3), semi-volatile organic compounds (SVOCs; with saturation concentration C∗ in the range 0.1– 103 μg m−3), or low-volatility organic compounds (LVOCs; with saturation concentration C∗ lower than 0.1 μg m−3; Lipsky and Robinson, 2006; Grieshop et al, 2009; Huffman et al, 2009; Cappa and Jimenez, 2010; Fountoukis et al, 2014; Tsimpidi et al, 2010; Woody et al, 2016; Ciarelli et al, 2017a, b)
For anthropogenic intermediate and semivolatile organic compound (I/S-VOC) emissions, the oxidation mechanism is based on the hybrid volatility basis set (1.5-D VBS) approach developed by Koo et al (2014)
Summary
Organic aerosols (OAs) are one of the main compound of submicron particulate matter (PM1; Jimenez et al, 2009). M. Chrit et al.: Organic aerosol concentrations during ChArMEx 2014 winter volatile in emissions inventories and chemistry-transport models (CTMs); recent studies have provided clear evidence that a large portion of POA emissions partition between the gas and the particle phases (Robinson et al, 2007). At Ersa, over the Mediterranean and during the summer, Chrit et al (2017) found high OM : OC and O : C ratios (2.5 and 1 respectively) They are due to aged biogenic OAs, which Chrit et al (2017) were able to represent by adding the formation of extremely low-volatility species and organic nitrate to the model and by considering the formation of organosulfate.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
