Volatility measurement of atmospheric submicron aerosols in an urban atmosphere in southern China

Abstract. Aerosol pollution has been a very serious environmental problem in China for many years. The volatility of aerosols can affect the distribution of compounds in the gas and aerosol phases, the atmospheric fates of the corresponding components and the measurement of the concentration of aerosols. Compared to the characterization of chemical composition, few studies have focused on the volatility of aerosols in China. In this study, a TD-AMS (Thermo-Denuder – Aerosol Mass Spectrometer) system was deployed to study the volatility of non-refractory PM1 species during winter in Shenzhen. To our knowledge, this paper is the first report of the volatilities of aerosol chemical components based on a TD-AMS system in China. The average PM1 mass concentration during the experiment was 42.7 ± 20.1 μg m−3, with organics being the most abundant component (43.2 % of the total mass). The volatility of chemical species measured by the AMS varied, with nitrate showing the highest volatility, with an MFR (mass fraction remaining) of 0.57 at 50 °C. Organics showed semi-volatile characteristics (the MFR was 0.88 at 50 °C), and the volatility had a relatively linear correlation with the TD temperature (from 50 to 200 °C), with an evaporation rate of 0.45 %·°C1. Five subtypes of OA were resolved from total OAs by PMF for data obtained under both ambient temperature and high temperatures through the TD, including a hydrocarbon-like OA (HOA, accounting for 13.5 %), a cooking OA (COA, 20.6 %), a biomass burning OA (BBOA, 8.9 %) and two oxygenated OAs (OOA): a less-oxidized OOA (LO-OOA, 39.1 %) and a more-oxidized OOA (MO-OOA, 17.9 %). Different OA species presented different volatilities; the volatility sequence of OA factors at 50 °C was HOA (MFR of 0.56) > LO-OOA (0.70) > COA (0.85) ≈ BBOA (0.87) > MO-OOA (0.99). The volatility sequence of OA components suggested that HOA, rather than BBOA or COA, could be a potentially important source of LO-OOA through the oxidizing process of Evaporation – Oxidation in gas phase – Condensation. The results above can contribute to the understanding of the formation and ageing of submicron aerosols in the atmosphere and will help to constrain aerosol modelling inputs.