Abstract
Abstract. Water-soluble organic carbon (WSOC) is a large fraction of organic aerosols (OA) globally and has significant impacts on climate and human health. The sources of WSOC remain very uncertain in polluted regions. Here we present a quantitative source apportionment of WSOC, isolated from aerosols in China using radiocarbon (14C) and offline high-resolution time-of-flight aerosol mass spectrometer measurements. Fossil emissions on average accounted for 32–47 % of WSOC. Secondary organic carbon (SOC) dominated both the non-fossil and fossil derived WSOC, highlighting the importance of secondary formation to WSOC in severe winter haze episodes. Contributions from fossil emissions to SOC were 61 ± 4 and 50 ± 9 % in Shanghai and Beijing, respectively, significantly larger than those in Guangzhou (36 ± 9 %) and Xi'an (26 ± 9 %). The most important primary sources were biomass burning emissions, contributing 17–26 % of WSOC. The remaining primary sources such as coal combustion, cooking and traffic were generally very small but not negligible contributors, as coal combustion contribution could exceed 10 %. Taken together with earlier 14C source apportionment studies in urban, rural, semi-urban and background regions in Asia, Europe and the USA, we demonstrated a dominant contribution of non-fossil emissions (i.e., 75 ± 11 %) to WSOC aerosols in the Northern Hemisphere; however, the fossil fraction is substantially larger in aerosols from East Asia and the eastern Asian pollution outflow, especially during winter, due to increasing coal combustion. Inclusion of our findings can improve a modelling of effects of WSOC aerosols on climate, atmospheric chemistry and public health.
Highlights
Water-soluble organic carbon (WSOC) is a large fraction of atmospheric organic aerosols (OA), which contributes approximately 10 to 80 % of the total mass of organic carbon (OC) in aerosols from urban, rural and remote sites (Zappoli et al, 1999; Weber et al, 2007; Ruellan and Cachier, 2001; Wozniak et al, 2012; Mayol-Bracero et al, 2002).Published by Copernicus Publications on behalf of the European Geosciences Union.Y.-L
Our study demonstrates that non-fossil emissions are generally a dominant contributor of WSOC aerosols during extreme haze events in representative major cities of China, which is in agreement with WSOC source information identified in aerosols with different size fractions (e.g., TSP, PM10 and PM2.5) observed in the Northern Hemisphere at urban, rural, semi-urban, and background sites in East/South Asia, Europe and USA (Table 1)
Low combustion efficiencies and high emission factors in most of the combustion processes in China may further be responsible for increased concentrations of fossil precursors which may be oxidized to form water-soluble secondary organic aerosol (SOA) in the atmosphere and contribute substantially to the WSOC aerosols
Summary
Water-soluble organic carbon (WSOC) is a large fraction of atmospheric organic aerosols (OA), which contributes approximately 10 to 80 % of the total mass of organic carbon (OC) in aerosols from urban, rural and remote sites (Zappoli et al, 1999; Weber et al, 2007; Ruellan and Cachier, 2001; Wozniak et al, 2012; Mayol-Bracero et al, 2002).Y.-L. Water-soluble organic carbon (WSOC) is a large fraction of atmospheric organic aerosols (OA), which contributes approximately 10 to 80 % of the total mass of organic carbon (OC) in aerosols from urban, rural and remote sites (Zappoli et al, 1999; Weber et al, 2007; Ruellan and Cachier, 2001; Wozniak et al, 2012; Mayol-Bracero et al, 2002). Recent studies suggest that the water-soluble fraction of humic like substances (HULIS) is a major component of WSOC, which exhibits light-absorbing properties (Limbeck et al, 2005; Andreae and Gelencser, 2006; Laskin et al, 2015). China Xi’an, China Shanghai, China Guangzhou, China Beijing, China Beijing, China Beijing, China Guangzhou, China Guangzhou, China Xi’an, China Xi’an, China Wuhan, China Sapporo, Japan Sapporo, Japan Sapporo, Japan Sapporo, Japan Sapporo, Japan Jeju Island, Korea Jeju Island, Korea Jeju Island, Korea
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