Light absorption by water-soluble organic carbon in atmospheric fine particles in the central Tibetan Plateau

Abstract. The mass absorption efficiency (MAE) of elemental carbon (EC) in Beijing was quantified using a thermal-optical carbon analyzer. The MAE measured at 632 nm was 8.45±1.71 and 9.41±1.92 m2 g−1 during winter and summer respectively. The daily variation of MAE was found to coincide with the abundance of organic carbon (OC), especially the OC to EC ratio, perhaps due to the enhancement by coating with organic aerosol (especially secondary organic aerosol, SOA) or the artifacts resulting from the redistribution of liquid-like organic particles during the filter-based absorption measurements. Using a converting approach that accounts for the discrepancy caused by measurements methods of both light absorption and EC concentration, previously published MAE values were converted to the equivalent-MAE, which is the estimated value if using the same measurement methods as used in this study. The equivalent-MAE was found to be much lower in the regions heavily impacted by biomass burning (e.g., below 2.7 m2 g−1 for two Indian cities). Results from source samples (including diesel exhaust samples and biomass smoke samples) also demonstrated that emissions from biomass burning would decrease the MAE of EC. Moreover, optical properties of water-soluble organic carbon (WSOC) in Beijing were presented. Light absorption by WSOC exhibited strong wavelength (λ) dependence such that absorption varied approximately as λ−7, which was characteristic of the brown carbon spectra. The MAE of WSOC (measured at 365 nm) was 1.79±0.24 and 0.71±0.20 m2 g−1 during winter and summer respectively. The large discrepancy between the MAE of WSOC during winter and summer was attributed to the difference in the precursors of SOA such that anthropogenic volatile organic compounds (AVOCs) should be more important as the precursors of SOA in winter. The MAE of WSOC in Beijing was much higher than results from the southeastern United States which were obtained using the same method as used in this study, perhaps due to the stronger emissions of biomass burning in China.

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Dual carbon isotope‐based source apportionment and light absorption properties of water‐soluble organic carbon in PM 2.5 over China

Journal of Geophysical Research Atmospheres ◽

10.1029/2020jd033920 ◽

2021 ◽

Author(s):

Yangzhi Mo ◽

Jun Li ◽

Zhineng Cheng ◽

Guangcai Zhong ◽

Sanyuan Zhu ◽

...

Keyword(s):

Organic Carbon ◽

Source Apportionment ◽

Carbon Isotope ◽

Light Absorption ◽

Water Soluble ◽

Absorption Properties ◽

Pm 2.5 ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

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A yearlong study of water-soluble organic carbon in Beijing II: Light absorption properties

Atmospheric Environment ◽

10.1016/j.atmosenv.2014.02.022 ◽

2014 ◽

Vol 89 ◽

pp. 235-241 ◽

Cited By ~ 86

Author(s):

Zhenyu Du ◽

Kebin He ◽

Yuan Cheng ◽

Fengkui Duan ◽

Yongliang Ma ◽

...

Keyword(s):

Organic Carbon ◽

Light Absorption ◽

Water Soluble ◽

Absorption Properties ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

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Sources and light absorption of water-soluble organic carbon aerosols in the outflow from northern China

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1413-2014 ◽

2014 ◽

Vol 14 (3) ◽

pp. 1413-1422 ◽

Cited By ~ 123

Author(s):

E. N. Kirillova ◽

A. Andersson ◽

J. Han ◽

M. Lee ◽

Ö. Gustafsson

Keyword(s):

Organic Carbon ◽

Light Absorption ◽

Radiative Forcing ◽

Large Fraction ◽

Northern China ◽

Water Soluble ◽

Cloud Formation ◽

Carbonaceous Aerosols ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

Abstract. High loadings of anthropogenic carbonaceous aerosols in Chinese air influence the air quality for over one billion people and impact the regional climate. A large fraction (17–80%) of this aerosol carbon is water-soluble, promoting cloud formation and thus climate cooling. Recent findings, however, suggest that water-soluble carbonaceous aerosols also absorb sunlight, bringing additional direct and indirect climate warming effects, yet the extent and nature of light absorption by this water-soluble "brown carbon" and its relation to sources is poorly understood. Here, we combine source estimates constrained by dual carbon isotopes with light-absorption measurements of water-soluble organic carbon (WSOC) for a March 2011 campaign at the Korea Climate Observatory at Gosan (KCOG), a receptor station in SE Yellow Sea for the outflow from northern China. The mass absorption cross section at 365 nm (MAC365) of WSOC for air masses from N. China were in general higher (0.8–1.1 m2 g−1), than from other source regions (0.3–0.8 m2 g−1). However, this effect corresponds to only 2–10% of the radiative forcing caused by light absorption by elemental carbon. Radiocarbon constraints show that the WSOC in Chinese outflow had significantly higher fraction fossil sources (30–50%) compared to previous findings in S. Asia, N. America and Europe. Stable carbon (δ13C) measurements were consistent with aging during long-range air mass transport for this large fraction of carbonaceous aerosols.

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Spatial and seasonal variations of fine particle water-soluble organic carbon (WSOC) over the Southeastern United States: implications for secondary organic aerosol formation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-9621-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 9621-9664 ◽

Cited By ~ 3

Author(s):

X. Zhang ◽

Z. Liu ◽

A. Hecobian ◽

M. Zheng ◽

N. H. Frank ◽

...

Keyword(s):

Organic Carbon ◽

Fine Particles ◽

Secondary Organic Aerosol ◽

Organic Aerosol ◽

Water Soluble ◽

Aerosol Formation ◽

Southeastern Us ◽

Urban Rural ◽

Water Soluble Organic Carbon ◽

Soluble Organic Carbon

Abstract. Secondary organic aerosol (SOA) in the Southeastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24 h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan < 50 ng m−3), WSOC and sulfate were highly correlated with PM2.5 mass and both comprised a large mass fraction of PM2.5 (13% and 35%, respectively). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly on the photochemical processes that lead to secondary formation. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC was associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55 mg C m−2 h−1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the Southeastern US, confirming the importance of secondary organic aerosol and the roles of both biogenic and anthropogenic emissions.

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