Lin Yue, Han Yuemei, Li Guohui, Li Lijuan, Zhang Xin, Cao Junji
Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Aerosol Chemistry and Physics, State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
Sci Total Environ. 2024 May 20;926:171820. doi: 10.1016/j.scitotenv.2024.171820. Epub 2024 Mar 19.
Atmospheric brown carbon (BrC) aerosols were investigated at two urban sites in southern (Hefei) and northern (Shijiazhuang) China during summer and winter of 2019-2020 to explore regional variability in their compositional and optical properties. Organic matter in ambient PM samples were characterized at molecular level using ultrahigh performance liquid chromatography coupled with a diode array detector and an Orbitrap mass spectrometer. Although the molecular composition of organic aerosols varied substantially over different ambient environments, they were mainly composed by CHO and CHON species in positive ionization mode while CHO and CHOS species in negative mode. The mass absorption coefficients of BrC aerosols at wavelength range 250-450 nm were relatively higher for winter samples in both cities and for Shijiazhuang samples in both seasons, partly attributed to the higher concentration levels of anthropogenic air pollutants in these environments. The absorption Ångström exponents further revealed that BrC aerosols in winter seasons and in Shijiazhuang had a greater capacity of absorption at shorter wavelengths. A total of 26 BrC species with strong absorption were unambiguously identified from different environments, which mainly consisted of CHO, CHON, and CHN species and had higher degrees of unsaturation and lower degrees of oxidation. The presence and abundance of these BrC species varied dynamically across the seasons and cities, with a greater number of species presented in the winter of Shijiazhuang. The BrC species together contributed 12-26 % in the total absorbance of light-absorbing organic components at 250-450 nm. This study highlights the regional differences in BrC properties influenced by the sources and atmospheric processes, which should be taken into account to assess their climate impacts.
2019 - 2020年夏季和冬季，在中国南方（合肥）和北方（石家庄）的两个城市站点对大气棕色碳（BrC）气溶胶进行了研究，以探讨其成分和光学特性的区域变异性。使用超高效液相色谱结合二极管阵列检测器和轨道阱质谱仪在分子水平上对环境PM样品中的有机物进行了表征。尽管有机气溶胶的分子组成在不同的环境中差异很大，但在正离子模式下它们主要由CHO和CHON物种组成，而在负离子模式下由CHO和CHOS物种组成。两个城市冬季样品以及石家庄两个季节的样品在250 - 450 nm波长范围内的BrC气溶胶质量吸收系数相对较高，部分原因是这些环境中人为空气污染物的浓度水平较高。吸收Ångström指数进一步表明，冬季和石家庄的BrC气溶胶在较短波长下具有更大的吸收能力。从不同环境中明确鉴定出总共26种具有强吸收的BrC物种，它们主要由CHO、CHON和CHN物种组成，具有较高的不饱和度和较低的氧化度。这些BrC物种的存在和丰度在季节和城市之间动态变化，石家庄冬季出现的物种数量更多。在250 - 450 nm波长下，BrC物种在吸光有机成分的总吸光度中贡献了12 - 26%。这项研究突出了受源和大气过程影响的BrC特性的区域差异，在评估其气候影响时应予以考虑。
