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Determining the Sources and Transport of Brown Carbon Using Radionuclide Tracers and Modeling
  • +8
  • Hongxing Jiang,
  • Jun Li,
  • Rong Sun,
  • Guoqing Liu,
  • Chongguo Tian,
  • Jiao Tang,
  • Zhineng Cheng,
  • Sanyuan Zhu,
  • Guangcai Zhong,
  • Xiang Ding,
  • Gan Zhang
Hongxing Jiang
Guangzhou Institute of Geochemistry

Corresponding Author:[email protected]

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Jun Li
Guangzhou Institute of Geochemistry
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Rong Sun
Guangzhou Institute of Geochemistry
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Guoqing Liu
Shenzhen University
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Chongguo Tian
Yantai Institute of Coastal Zone Research
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Jiao Tang
Guangzhou Institute of Geochemistry
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Zhineng Cheng
Guangzhou Institute of Geochemistry
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Sanyuan Zhu
Guangzhou Institute of Geochemistry
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Guangcai Zhong
Guangzhou Institute of Geochemistry
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Xiang Ding
Guangzhou Institute of Geochemistry
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Gan Zhang
Guangzhou Institute of Geochemistry
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Abstract

The isotope tracer technique plays a key role in identifying the sources and atmospheric processes affecting pollution. The sources of brown carbon (BrC) at Guangzhou during 2017-2018 was characterized by positive matrix factorization with carbon isotope constraints and multiple linear regression analysis. The primary emission factors of fossil fuel combustion (FF) and biomass burning (BB) accounted for 34% and 27% of dissolved BrC absorption at λ = 365 nm, respectively. The total mean light absorption contributed by secondary sources was 39%. The absorption of FF-origin BrC was relatively stable and dominant in the summer monsoon period, whereas the absorption of BrC from BB and secondary nitrate formation increased and contributed larger fractions during the winter monsoon period. Transported BrC was estimated using an index of 7 Be/(7 Be+n 210 Pb). Higher values were generally accompanied by lower BrC absorption, whereas lower values were associated with higher BrC absorption, indicating that BrC absorption of aerosols transported from the upper-atmosphere is lower than that of aerosols transported near the surface. Based on the positive correlations between 210 Pb and BrC absorption and non-fossil dissolved organic carbon in the winter monsoon period, we estimated that the contribution of invasive BrC (include ground and upper-atmosphere level) to total absorption during the period of elevated BrC was approximately 50%, which was likely related to BB organic aerosols and secondary nitrate formation processes. This study supports radionuclides as a novel method for characterizing the sources and transport of BrC that can be applied in future atmospheric research.