Difference in production routes of water-soluble organic carbon in PM_2.5observed during non-biomass and biomass burning periods in Gwangju, Korea

Abstract

4 h integrated PM2.5 samples were collected from an urban site of Gwangju, Korea, for five days and analyzed for organic carbon and elemental carbon (OC and EC), total water-soluble OC (WSOC), hydrophilic and hydrophobic WSOC fractions (WSOCHPI and WSOCHPO), oxalate, and inorganic ionic species (sodium (Na(+)), ammonium (NH4(+)), potassium (K(+)), calcium (Ca(2+)), magnesium (Mg(2+)), chloride (Cl(-)), nitrate (NO3(-)), and sulfate (SO4(2-))) to investigate the possible sources of water-soluble organic aerosols. Two types of sampling periods were classified according to the regression relationship between black carbon (BC) concentrations measured at wavelengths of 370 nm (BC370nm) and 880 nm (BC880nm) using an aethalometer; the first period was traffic emission influence ("non-biomass burning (BB) period") and the second was biomass burning influence ("BB period"). The slope of the regression equation (BC370nm/BC880nm) was 0.95 for the non-BB period and 1.29 for the BB period. However, no noticeable difference in the WSOC/OC ratio, which can be used to infer the extent of secondary organic aerosol (SOA) formation, was found between the non-BB (0.61, range = 0.43-0.75) and BB (0.61, range = 0.52-0.68) periods, due to significant contribution of primary BB emissions to the WSOC. The concentrations of OC, WSOC and K(+), which were used as the BB emission markers, were 15.7 μg C m(-3) (11.5-24.3), 9.4 μg C m(-3) (7.0-12.7), and 1.2 μg m(-3) (0.6-2.7), respectively, during the BB period, and these results were approximately 1.7, 1.7, and 3.9 times higher than those during the non-BB period. During the non-BB period, good correlations among WSOC, SO4(2-) and oxalate, and poor correlations among WSOC, EC, and K(+) suggest that SOA is probably an important source of WSOC (and WSOCHPI) concentration. For the WSOC fractions, better correlations among WSOCHPI, oxalate (R(2) = 0.52), and SO4(2-) (R(2) = 0.57) were found than among WSOCHPO, oxalate (R(2) = 0.23), and SO4(2-) (R(2) = 0.20), suggesting that a significant proportion of the WSOCHPI fraction of OC could be produced through processes (gas-phase and heterogeneous oxidations) such as SOA formation. However, during the BB period, the BB emission source accounted for the high correlations between total WSOC (and WSOC fractions) and other relevant atmospheric parameters (EC, Na(+), Cl(-), K(+), and oxalate), with higher correlations in WSOCHPI than in WSOCHPO. These results suggest a significant contribution of BB emissions to WSOC.

Source identification of water-soluble organic aerosols at a roadway site using a positive matrix factorization analysis

“…Biomass burning (BB) is a significant primary source of WSOC Zhang et al, 2010;Du et al, 2014;Yu et al, 2014;Kuang et al, 2015). WSOC is often considered a proxy for secondary organic aerosols (SOA) due to its highly oxidized nature (Weber et al, 2007;Park et al, 2013a;Yu et al, 2014;Kuang et al, 2015). In addition to BB emissions and SOA, traffic emissions are known primary sources of particulate WSOC (Ruellan and Cachier, 2001;Ho et al, 2006;Saarikoski et al, 2008;Cho and Park, 2013;Park et al, 2013a).…”

“…It is emitted directly from combustion sources, and is formed by the gas-to-particle conversion processes (Seinfeld and Pandis, 2006). Biomass burning (BB) is a significant primary source of WSOC Zhang et al, 2010;Du et al, 2014;Yu et al, 2014;Kuang et al, 2015). WSOC is often considered a proxy for secondary organic aerosols (SOA) due to its highly oxidized nature (Weber et al, 2007;Park et al, 2013a;Yu et al, 2014;Kuang et al, 2015).…”

Chemical Characteristics and Formation Pathways of Humic Like Substances (HULIS) in PM_2.5 in an Urban Area

“…따라서 본 연구에서는 도시지역 에서 약 1년 동안 PM 2.5 를 측정하여 WSOC의 상당한 부분을 차지하고 있는 HULIS의 일반적 화학 특성과 생성과정을 조사하였다. (Park et al, 2013a;Park and Shin, 2013;Jeong et al, 2011 Yu et al, 2014;Park et al, 2013a Park et al, 2013a;Park and Cho, 2011;Kondo et al, 2007;. …”

Investigation of the CCN Activity, BC and UVBC Mass Concentrations of Biomass Burning Aerosols during the 2013 BASELInE Campaign

“…7. Yu et al (2014) reported that the slope of the equation for the regression between BC 370nm and BC 880nm is 0.95 for the non-BB period and 1.29 for the BB period, which correspond to BC 880nm /BC 370nm values of 1.05 (non-BB) and 0.77 (BB) here. As seen in Fig.…”

“…Previous studies using aethalometer measurements have suggested that certain organic aerosol components such as aromatic organic species of wood smoke or BB aerosols have enhanced UV absorption at 370 nm, relative to that at 880 nm (Jeong et al, 2004;Park et al, 2006;Sandradewi et al, 2008;Kumar et al, 2011;Wang et al, 2011;Yu et al, 2014). Therefore, the ratio between BC concentrations measured at wavelengths of 880 nm (BC 880nm ) and 370 nm (BC 370nm ), also known as UVBC, as well as the Delta-C value (BC 370nm −BC 880nm ) were calculated and plotted in Fig.…”