Investigation of Primary and Secondary Particulate Brown Carbon in Two Chinese Cities of Xi’an and Hong Kong in Wintertime

Abstract

Brown carbon (BrC), an aerosol carbonaceous matter component, impacts atmospheric radiation and global climate because of its absorption in the near-ultraviolet−visible region. Simultaneous air sampling was conducted in two megacities of Xi'an (northern) and Hong Kong (southern) in China in winter of 2016−2017. The aim of this study is to determine and characterize the BrC compounds in collected filter samples. Characteristic absorption peaks corresponding to aromatic C−C stretching bands, organo-nitrates, and CO functional groups were seen in spectra of Xi'an samples, suggesting that the BrC was derived from freshly smoldering biomass and coal combustion as well as aqueous formation of anthropogenic secondary organic carbon. In Hong Kong, the light absorption of secondary BrC accounted for 76% of the total absorbances of BrC. The high abundance of strong CO groups, biogenic volatile organic compounds (BVOCs) and atmospheric oxidants suggest secondary BrC was likely formed from photochemical oxidation of BVOCs in Hong Kong. Several representative BrC molecular markers were detected using Fourier transform ion cyclotron resonance mass spectrometry and their absorption properties were simulated by quantum chemistry. The results demonstrate that light absorption capacities of secondary anthropogenic BrC with nitro-functional groups were stronger than those of biogenic secondary BrC and anthropogenic primary BrC.

Determining the Sources and Transport of Brown Carbon Using Radionuclide Tracers and Modeling

“…The ratio in GZ is lower than those in BB‐influenced areas, such as Beijing (58%) (Du et al., 2014), Atlanta (50%) (Hecobian et al., 2010), and Alabama (87%) (Washenfelder et al., 2015), but higher than that in a less‐polluted region of North Carolina (14%) (Xie, Chen, Holder, et al., 2019). Furthermore, we found that the contributions of secondary sources to total BrC absorption in Guangzhou (39%) was in the range measured in the wintertime of North China cities ( λ = 370 nm, 19%–48%), but much lower than those recorded on the Tibetan Plateau (70%) and Hong Kong (76%) (Wang, Han, et al., 2019; Wang, Ye, et al., 2019; Zhang et al., 2020), highlighting the dominant contribution of primary BrC in Guangzhou and the nonnegligible contributions from secondary BrC. Among secondary sources, NT is the most important source of secondary BrC, accounting for 16.4% of total BrC absorption.…”

Determining the Sources and Transport of Brown Carbon Using Radionuclide Tracers and Modeling

“…The ratio in GZ is lower than those in BB-influenced areas, such as Beijing (58%) (Du et al, 2014), Atlanta (50%) (Hecobian et al, 2010), and Alabama (87%) (Washenfelder et al, 2015), but higher than that in a less-polluted region of North Carolina (14%) . Furthermore, we found that the contributions of secondary sources to total BrC absorption in Guangzhou (39%) was in the range measured in the wintertime of North China cities (λ = 370 nm, 19%-48%), but much lower than those recorded on the Tibetan Plateau (70%) and Hong Kong (76%) (Wang, Han, et al, 2019;Zhang et al, 2020), highlighting the dominant contribution of primary BrC in Guangzhou and the nonnegligible contributions from secondary BrC. Among secondary sources, NT is the most important source of secondary BrC, accounting for 16.4% of total BrC absorption.…”

Characterizing Atmospheric Brown Carbon and Its Emission Sources during Wintertime in Shanghai, China

“…The pyrolysis of lignin during biomass burning usually produces a variety of substituted phenols; subsequently, nitrophenol is generated through phenolic compounds with NO x . Overall, there were nine element formulae identified as nitroaromatic compounds, eight of which were also detected in Xie et al Five of the nitroaromatic compounds (including 4-nitrophenol, 4-nitrocatechol, 2-nitro-1-naphthol, 3-methyl-4-nitrocatechol and 2-methyl-4nitrophenol) usually come from biomass burning or are produced from the photo-oxidation of anthropogenic VOCs (e.g., toluene, benzene) under high-NO x in heavy traffic urban environments [58,59]. Moreover, C 10 H 17 NO 7 S (RT = 11.186 min) may be a nitroxy organic sulfate derived from monoterpenes, and C 8 H 18 O 4 S (RT = 13.446 min) detected in the sample may be an aliphatic organic sulfate [60].…”