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Light attenuation versus evolved carbon (AVEC) – A new way to look at elemental and organic carbon analysis
Atmospheric Environment ( IF 5 ) Pub Date : 2018-02-01 , DOI: 10.1016/j.atmosenv.2017.12.011
E.M.G. Nicolosi , P. Quincey , A. Font , G.W. Fuller

Abstract The Attenuation Versus Evolved Carbon (AVEC) plot is a new way to represent thermal-optical organic carbon/elemental carbon (OC/EC) analysis data. The accumulated carbon concentration is plotted against the attenuation (ln (I0/I)). Unlike the thermogram, it provides information about the sample properties rather than the instantaneous instrument sensor status. The plot can be used to refine the determination of OC and EC split point, either from consideration of laser instability or transit time within the instrument; to investigate the optical properties of the particles; and to spot the early evolution of pyrolysed carbon (PC) and/or EC during the inert phase. 168 samples from three sites were studied. The gradient of the AVEC plot curve in the oxygenated phase provides information about the mass absorption cross section (σ) of the particles leaving the filter. The σ of the PC generated in the higher temperature Quartz protocol was greater than the PC generated in the lower temperature EUSAAR_2 protocol. Also, in both cases the PC evolved at a lower temperature in the oxygenated phase than the native EC. To minimise the shadowing effect, σ was also measured for the particles leaving the filter at the end of the analysis. These σ values, which are expected to be a combination of inherent σ together with fixed instrumental factors, were consistent between the different sites (45 ± 10 m2 g−1 in rural samples, 42 ± 8 m2 g−1 in urban samples and 35 ± 14 m2 g−1 in roadside samples). The AVEC plot can be generated from the data routinely produced by the analytical instrument using the R-code supplied in the supplementary material.

中文翻译:

光衰减与演化碳 (AVEC) – 一种看待元素和有机碳分析的新方法

摘要 衰减与演化碳 (AVEC) 图是一种表示热光有机碳/元素碳 (OC/EC) 分析数据的新方法。累积碳浓度与衰减 (ln (I0/I)) 作图。与热谱图不同,它提供有关样品特性的信息,而不是瞬时仪器传感器状态。该图可用于细化 OC 和 EC 分裂点的确定,无论是考虑激光不稳定性还是仪器内的传输时间;研究粒子的光学特性;并在惰性阶段发现热解碳 (PC) 和/或 EC 的早期演变。研究了来自三个地点的 168 个样品。含氧相中 AVEC 绘图曲线的梯度提供有关离开过滤器的颗粒的质量吸收截面 (σ) 的信息。在较高温度 Quartz 协议中生成的 PC 的 σ 大于在较低温度 EUSAAR_2 协议中生成的 PC。此外,在这两种情况下,PC 在氧化相中的演化温度低于天然 EC。为了最小化阴影效应,还在分析结束时对离开过滤器的粒子测量了 σ。这些 σ 值预计是固有 σ 与固定工具因素的组合,在不同地点之间是一致的(农村样本为 45 ± 10 m2 g-1,城市样本为 42 ± 8 m2 g-1 和 35 ± 14 m2 g−1(路边样品)。
更新日期:2018-02-01
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