Photochemical aging of aerosol particles in different air masses arriving at Baengnyeong Island, Korea

Abstract

Abstract. Atmospheric aerosol particles are a serious health risk, especially in regions like East Asia. We investigated the photochemical aging of ambient aerosols using a potential aerosol mass (PAM) reactor at Baengnyeong Island in the Yellow Sea during 4–12 August 2011. The size distributions and chemical compositions of aerosol particles were measured alternately every 6 min from the ambient air or through the highly oxidizing environment of a potential aerosol mass (PAM) reactor. Particle size and chemical composition were measured by using the combination of a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Inside the PAM reactor, O3 and OH levels were equivalent to 4.6 days of integrated OH exposure at typical atmospheric conditions. Two types of air masses were distinguished on the basis of the chemical composition and the degree of aging: air transported from China, which was more aged with a higher sulfate concentration and O : C ratio, and the air transported across the Korean Peninsula, which was less aged with more organics than sulfate and a lower O : C ratio. For both episodes, the particulate sulfate mass concentration increased in the 200–400 nm size range when sampled through the PAM reactor. A decrease in organics was responsible for the loss of mass concentration in 100–200 nm particles when sampled through the PAM reactor for the organics-dominated episode. This loss was especially evident for the m∕z 43 component, which represents less oxidized organics. The m∕z 44 component, which represents further oxidized organics, increased with a shift toward larger sizes for both episodes. It is not possible to quantify the maximum possible organic mass concentration for either episode because only one OH exposure of 4.6 days was used, but it is clear that SO2 was a primary precursor of secondary aerosol in northeast Asia, especially during long-range transport from China. In addition, inorganic nitrate evaporated in the PAM reactor as sulfate was added to the particles. These results suggest that the chemical composition of aerosols and their degree of photochemical aging, particularly for organics, are also crucial in determining aerosol mass concentrations.

Secondary organic aerosol production from local emissions dominates the organic aerosol budget over Seoul, South Korea, during KORUS-AQ

“…The potential aerosol mass (PAM) OFR measures the aerosol mass that can be formed from the precursors that are present in ambient or laboratory air (Kang et al, 2007;Lambe et al, 2011). The OFR has been successfully deployed in multiple urban and forested locations to quantify potential SOA Kang et al, 2018). The chemical regimes and comparability to ambient results of the OFR have been characterized extensively by modeling, which indicate that SOA formation proceeds by chemistry similar to that in the atmosphere, dominated by OH oxidation under low-NO conditions (Li et al, 2015;Peng et al, 2015Peng et al, , 2016.…”

“…This box model does not explicitly consider volatile chemical products (VCPs) (Khare and Gentner, 2018;McDonald et al, 2018), S/IVOC from cooking emissions (e.g., Hayes et al, 2013;Ots et al, 2016), or glyoxal (Volkamer et al, 2006;Knote et al, 2014), although contributions from these components may be partially included in the empirical estimation of S/IVOC. Modeled SOA in Los Angeles, using estimates of S/IVOC from HOA/ CO, including approximately two-thirds of VCPs and not including glyoxal, was able to capture the observed SOA in the first 0.5 equivalent Figure 11.…”

Secondary Organic Aerosol Production from Local Emissions Dominates the Organic Aerosol Budget over Seoul, South Korea, during KORUS-AQ

“…The OFR has been successfully deployed in multiple 266 urban and forested locations to quantify potential SOA (Ortega et al, 2016;Palm et al, 2016Palm et al, , 267 2017Palm et al, , 2018Kang et al, 2018). The chemical regimes and comparability to ambient results of the 268 OFR have been characterized extensively by modeling, which indicate that SOA formation 269 proceeds by chemistry similar to the atmosphere, dominated by OH oxidation under low-NO 270 conditions Peng et al, 2015Peng et al, , 2016 Fig.…”

Physical and chemical constraints on transformation and mass-increase of fine aerosols in northeast Asia

“…7a). The mass size distributions of OC, NO3 -, and SO4 -2 estimated by the aerosol mass spectrometer generally show organics enriched in nucleation-mode particles (e.g., Kang et al, 2018;Kim et al, 2018).…”