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

Abstract

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 thermodenuder aerosol mass spectrometer (TD-AMS) system was deployed to study the volatility of non-refractory submicron particulate matter (PM 1 ) 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 PM 1 mass concentration during the experiment was 42.7±20.1 µg m −3 , with organic aerosol (OA) 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 a mass fraction remaining (MFR) of 0.57 at 50 • C. Organics showed semivolatile characteristics (the MFR was 0.88 at 50 • C), and the volatility had a relatively linear correlation with the TD temperature (from the ambient temperature to 200 • C), with an evaporation rate of 0.45 % • C −1 . Five subtypes of OA were resolved from total OA using positive matrix factorization (PMF) for data obtained under both ambient temperature and high temperatures through the TD, including a hydrocarbonlike OA (HOA, accounting for 13.5 %), a cooking OA (COA, 20.6 %), a biomass-burning OA (BBOA, 8.9 %), and two oxygenated OAs (OOAs): a less-oxidized OOA (LO-OOA, 39.1 %) and a more-oxidized OOA (MO-OOA, 17.9 %). Different OA factors presented different volatilities, and the volatility sequence of the 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), which was not completely consistent with the sequence of their O / C ratios. The high volatility of HOA implied that it had a high potential to be oxidized to secondary species in the gas phase. The aerosol volatility measurement results in this study provide useful parameters for the modeling work of aerosol evolution in China and are also helpful in understanding the formation mechanisms of secondary aerosols.

Summertime aerosol volatility measurements in Beijing, China

“…In addition, OA consisted of ∼ 13 % extremely lowvolatility compounds (ELVOCs with C * ≤ 10 −4 µg m −3 ), consistent with the remaining organic mass fraction at 226 • C (9 %). The SVOC fraction in Beijing in summer 2018 was overall larger than those reported in Finokalia (30 %-60 %) (Lee et al, 2010), Athens (38 %) (Louvaris et al, 2017), Centreville and Raleigh (60 %) (Saha et al, 2017), and Mexico City (39 %-73 %; Cappa and Jimenez, 2010). Such results might suggest relatively higher volatility of OA in summer in Beijing than at other sites, consistent with the fact that the fraction of evaporated particulate organics (28 %) at 50 • C was larger than that observed in Shenzhen (∼ 10 %) , Centreville and Raleigh (Kostenidou et al, 2018;Saha et al, 2017), and Athens (Louvaris et al, 2017).…”

“…A number of studies have been conducted to investigate the OA volatility using thermogram models assuming fixed effective vaporization enthalpy and mass accommodation coefficient (Cappa and Jimenez, 2010;Lee et al, 2010;Paciga et al, 2016;Louvaris et al, 2017;Kostenidou et al, 2018). The results showed that OA volatility distributions may vary from place to place, and the estimated OA volatility was sensitive to the assumed values of the effective vaporization enthalpy and the mass accommodation coefficient (Riipinen et al, 2010).…”

High contributions of fossil sources to more volatile organic aerosol

“…For the PM 2.5 samples collected in Xi'an, filter pieces of 1.5 cm 2 were taken for OC and EC analysis using a carbon analyzer (Model 5L, Sunset Laboratory, Inc., Portland, OR, USA) following the thermal-optical transmittance protocol EUSAAR_2 (European Supersites for Atmospheric Aerosol Research; Cavalli et al, 2010). The EUSAAR_2 protocol de-fines OC1 as the carbon fraction that desorbs in helium (He) at 200 • C for 2 min.…”

A Review of Aerosol Chemical Composition and Sources in Representative Regions of China during Wintertime

“…Figure 2b shows the relative contributions of the main organic sources. The terms of low-volatility OOA (LV-OOA) and semi-volatile OOA (SV-OOA) were originally used, whilst newer studies referred to more oxidized OOA (MO-OOA) and less-oxidized OOA (LO-OOA) [22,31,35,[43][44][45]. The OOAs at different aging levels are formed through different atmospheric processes (e.g., aqueous phase reactions and photochemical reactions).…”