Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology , Nanjing 210044, China.
Department of Environmental Toxicology, University of California at Davis , Davis, California 95616, United States.
Environ Sci Technol. 2017 Dec 19;51(24):14072-14082. doi: 10.1021/acs.est.7b03973. Epub 2017 Nov 28.
Refractory black carbon (rBC) aerosol is an important climate forcer, and its impacts are greatly influenced by the species associated with rBC cores. However, relevant knowledge is particularly lacking at the Tibetan Plateau (TP). Here we report, for the first time, highly time-resolved measurement results of rBC and its coating species in central TP (4730 m a.s.l), using an Aerodyne soot particle aerosol mass spectrometer (SP-AMS), which selectively measured rBC-containing particles. We found that the rBC was overall thickly coated with an average mass ratio of coating to rBC (R) of ∼7.7, and the coating species were predominantly secondarily formed by photochemical reactions. Interestingly, the thickly coated rBC was less oxygenated than the thinly coated rBC, mainly due to influence of the transported biomass burning organic aerosol (BBOA). This BBOA was relatively fresh but formed very thick coating on rBC. We further estimated the "lensing effect" of coating semiquantitatively by comparing the measurement data from a multiangle absorption photometer and SP-AMS, and found it could lead to up to 40% light absorption enhancement at R > 10. Our findings highlight that BBOA can significantly affect the "lensing effect", in addition to its relatively well-known role as light-absorbing "brown carbon."
难处理黑碳（rBC）气溶胶是一种重要的气候强迫因子，其影响受与 rBC 核心相关的物质的极大影响。然而，在青藏高原（TP），相关知识特别缺乏。在这里，我们首次报道了利用 Aerodyne soot particle 气溶胶质谱仪（SP-AMS）在青藏高原中部（4730 m 海拔）进行的高时间分辨率 rBC 及其涂层物质的测量结果，该仪器可选择性地测量含有 rBC 的颗粒。我们发现，rBC 总体上被厚厚的涂层包裹，涂层与 rBC 的平均质量比（R）约为 7.7，涂层物质主要是由光化学反应形成的二次物质。有趣的是，与薄涂层 rBC 相比，厚涂层 rBC 的含氧量较低，主要是由于运输的生物质燃烧有机气溶胶（BBOA）的影响。这种 BBOA 相对较新，但在 rBC 上形成了非常厚的涂层。我们通过比较多角度吸收光度计和 SP-AMS 的测量数据，进一步半定量地估计了涂层的“聚光效应”，发现当 R > 10 时，它可以导致高达 40%的光吸收增强。我们的研究结果表明，除了其作为光吸收“棕色碳”的相对知名作用外，BBOA 还可以显著影响“聚光效应”。
