Optical Calibration and Equivalence of a Multiwavelength Thermal/Optical Carbon Analyzer
Optical Calibration and Equivalence of a Multiwavelength Thermal/Optical Carbon Analyzer
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DOI：
10.4209/aaqr.2015.02.0106
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发表时间：
2015
影响因子：
4
通讯作者：
J. Chow;Xiaoliang Wang;B. Sumlin;S. Gronstal;L. Chen;D. Trimble;S. Kohl;Sierra R. Mayorga;Gustavo M. Riggio;Patrick R. Hurbain;Megan M. Johnson;R. Zimmermann;J. Watson
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文献类型：
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作者：
J. Chow;Xiaoliang Wang;B. Sumlin;S. Gronstal;L. Chen;D. Trimble;S. Kohl;Sierra R. Mayorga;Gustavo M. Riggio;Patrick R. Hurbain;Megan M. Johnson;R. Zimmermann;J. Watson
有机碳和元素碳(OC和EC)是由测量过程在操作上定义的，因此长期趋势可能会因仪器的变化而中断。研究了对美国改进的碳分析协议和硬件的修改，用从405到980 nm的7个波长取代用于OC炭化调整的633 nm激光，其中一个波长在635 nm。每个波长的反射率(R)和透射率(T)值可通过传递标准追溯到初级标准，传递标准由过滤介质上的气溶胶沉积范围组成，与分析样品的气溶胶沉积范围相似。用这些标准校准的UV/VIS光谱仪将R值和T值分配给这些滤光片。使用环境和源(例如，柴油废气、燃烧的生物质和阴燃的生物质)样品，证明了R和T校准与样品类型无关。城市和非城市样品的总碳(TC)、OC和EC与早期硬件设计的比较表明，在重复分析得出的精度内，633 nm和635 nm波长的等价性。确定了额外的多波长信息的几种用途，包括：1)多光谱遥感传感器的地面真实情况；2)改进对地球辐射平衡的估计；3)将特定的有机化合物与其光吸收特性联系起来；以及4)适当的黑碳和棕碳来源。
ABSTRACTOrganic and elemental carbon (OC and EC) are operationally-defined by the measurement process, so long-term trends may be interrupted with instrumentation changes. A modification to the U.S. IMPROVE carbon analysis protocol and hardware is examined that replaces the 633 nm laser light used for OC charring adjustments with seven wavelengths ranging from 405 to 980 nm, including one at 635 nm. Reflectance (R) and Transmittance (T) values for each wavelength are made traceable to primary standards through transfer standards consisting of a range of aerosol deposits on filter media similar to that of the analyzed samples. R and T values are assigned to these filters using a UV/VIS spectrometer calibrated with these standards. Using ambient and source (e.g., diesel exhaust, flaming biomass, and smoldering biomass) samples, it is demonstrated that R and T calibration is independent of the sample type. Total carbon (TC), OC, and EC comparisons with the earlier hardware design for urban- and non-urban samples demonstrate equivalence, within precisions derived from replicate analyses, for the 633 nm and 635 nm wavelengths. Several uses of the additional multiwavelength information are identified, including: 1) ground-truthing of multi-spectral remote sensors; 2) improving estimates of the Earth’s radiation balance; 3) associating specific organic compounds with their light absorption properties; and 4) appropriating sources of black and brown carbon.