Chemical characteristics of water‐soluble organic carbon in the Asian outflow

Abstract

[1] Semicontinuous measurements of water-soluble organic carbon (WSOC) and organic carbon (OC) in PM 2.5 were made at Gosan, Korea, in March-April 2005. On average, the WSOC/OC mass ratio for all air masses observed at Gosan was 0.30 ± 0.12. WSOC correlated well with CO (r 2 = 0.54) in Chinese outflow, suggesting that a major part of the observed WSOC and/or their precursors was of combustion origin. The relationship between the increase of WSOC and O 3 suggests that the observed WSOC was mostly secondary product. To interpret the measured organic compounds, thermal analyses of organic standards were made in the laboratory. Thermograms of a single standard of water-soluble organic species showed that carbon that evolved at high temperatures (600°-870°C) was generally associated with water-soluble compounds having high molecular weights (MWs) on the order of hundreds, while carbon that evolved at low temperatures (<300°C) generally had MWs of less than $180 g mol À1 . Positive matrix factorization (PMF) analysis revealed three organic compound groups (low, medium, and highly refractory compounds) based on the OC thermograms. On average, highly and low refractory compound groups accounted for 79% and 21% of the WSOC mass, respectively, at Gosan. Highly refractory compound groups significantly contributed to WSOC regardless of air mass origin. The results of the laboratory experiments imply that a large fraction of these highly refractory compound groups was likely associated with high MW compounds. For water-insoluble organic carbon(=OC-WSOC), medium and low refractory compound groups accounted for 60% and 40%, respectively, consistent with the results of the laboratory experiments.

Water-soluble organic carbon (WSOC) and its temperature-resolved carbon fractions in atmospheric aerosols in Beijing

“…It was suggested that the evolution features of carbon, such as the number and position of the peaks, are greatly influenced by the chemical composition of the aerosols (Yu et al, 2002). Investigation of thermograms of single standards of water-soluble organic species found that organics evolved at lower temperatures (such as oxalic acid, adipit acid and glucose) are generally associated with low molecular weight polar organic and organics evolved at higher temperatures (such as humic acid) might be associated with high molecular weight polar compounds (Matsumoto et al, 2014;Miyazaki et al, 2007;Yu et al, 2004). Therefore, the carbon fractions of WSOC in ascending Fig.…”

“…Although a number of studies have focused on chemical characteristics and sources of WSOC (Cheng et al, 2012;Huang et al, 2006;Miyazaki et al, 2007;Park et al, 2015), studies about the artifacts of WSOC during sampling, thermal characteristics of WSOC and its application to source appointment were limited. In our study, we developed a method to obtain the temperature-resolved carbon fractions of WSOC.…”

Stabilization of the Mass Absorption Cross Section of Black Carbon for Filter-Based Absorption Photometry by the use of a Heated Inlet

“…The air sample was introduced into a cyclone with a 50% effective cut-off diameter of 2.5 µm (PM 2.5 ) or 1 µm (PM 1 ) to exclude coarse particles. in the TMA and at Gosan estimated by combining the measurements at these sites Shiraiwa et al 2007;Miyazaki et al 2007;Kuwata et al 2007;Miyakawa et al 2008;Sahu et al 2009) are summarized in Table 2. Here OOA (nearly equivalent to SOA) and D p represent oxygenated organic aerosol and particle diameter, respectively.…”

Modal Characteristics of Elemental and Organic Carbon in an Urban Location in Guangzhou, China

“…PMF is a variant of factor analysis and the model details have been described by Paatero and coworkers (e.g., Paatero 1997;Paatero and Tapper 1994). Yu et al (2004) and Miyazaki et al (2007) used PMF to deconvolute mixtures of water-soluble OC in aerosol water extracts into three component groups of low, medium, and high molecular weight polar compounds on the basis of their thermal evolution features. In this study we carried out PMF analysis (PMF2, version 4.2) of the 98 samples (7 sets × 14 stages/set), with OC 1 , OC 2 , OC 3 , OC 4 , EC 1 , EC 2 , EC 3 , EC 4 , and EC 5 as the input variables.…”