Oak Ridge Institute for Science and Education (ORISE), 109 T.W. Alexander Drive, Research Triangle Park, NC, 27711, USA.
U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 109 T.W. Alexander Drive, Research Triangle Park, NC, 27711, USA.
Sci Rep. 2017 Aug 4;7(1):7318. doi: 10.1038/s41598-017-06981-8.
Light-absorbing organic carbon (OC), also termed brown carbon (BrC), from laboratory-based biomass burning (BB) has been studied intensively to understand the contribution of BB to radiative forcing. However, relatively few measurements have been conducted on field-based BB and even fewer measurements have examined BrC from anthropogenic combustion sources like motor vehicle emissions. In this work, the light absorption of methanol-extractable OC from prescribed and laboratory BB and gasoline vehicle emissions was examined using spectrophotometry. The light absorption of methanol extracts showed a strong wavelength dependence for both BB and gasoline vehicle emissions. The mass absorption coefficients at 365 nm (MAC, m gC) - used as a measurement proxy for BrC - were significantly correlated (p < 0.05) to the elemental carbon (EC)/OC ratios when examined by each BB fuel type. No significant correlation was observed when pooling fuels, indicating that both burn conditions and fuel types may impact BB BrC characteristics. The average MAC of gasoline vehicle emission samples is 0.62 ± 0.76 m gC, which is similar in magnitude to the BB samples (1.27 ± 0.76 m gC). These results suggest that in addition to BB, gasoline vehicle emissions may also be an important BrC source in urban areas.
吸光有机碳（OC），也称为棕色碳（BrC），来自实验室生物质燃烧（BB），已被深入研究，以了解 BB 对辐射强迫的贡献。然而，对基于现场的 BB 的测量相对较少，对来自人为燃烧源（如机动车排放）的 BrC 的测量甚至更少。在这项工作中，使用分光光度法研究了从规定的和实验室的 BB 以及汽油车排放物中提取的甲醇可溶 OC 的光吸收。甲醇提取物的光吸收对 BB 和汽油车排放物都表现出很强的波长依赖性。在分别检查每种 BB 燃料类型时，365nm 处的质量吸收系数（MAC，m gC） - 用作 BrC 的测量代理 - 与元素碳（EC）/OC 比值显著相关（p < 0.05）。当将燃料混合时，没有观察到显著的相关性，这表明燃烧条件和燃料类型都可能影响 BB BrC 的特征。汽油车排放样品的平均 MAC 为 0.62 ± 0.76 m gC，与 BB 样品（1.27 ± 0.76 m gC）的大小相似。这些结果表明，除了 BB 之外，汽油车排放物也可能是城市地区的一个重要 BrC 来源。
