Aerosol light absorption, black carbon, and elemental carbon at the Fresno Supersite, California
Aerosol light absorption, black carbon, and elemental carbon at the Fresno Supersite, California
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DOI：
10.1016/j.atmosres.2009.04.010
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发表时间：
2009-08-01
影响因子：
5.5
通讯作者：
Motallebi, Nehzat
中科院分区：
文献类型：
--
作者：
Chow, Judith C.;Watson, John G.;Motallebi, Nehzat
粒子光吸收（B（ap）），炭黑（BC），元素碳（EC）的测量在弗雷斯诺Supersite在2005年夏天进行了比较，以检查当前技术的等效性，评估基于过滤器的B（ap）校正方法，并确定EC质量吸收效率（σ（ap））和光谱依赖性的B（ap）。光声分析仪（PA）被用作原位B（ap）的基准。大多数B（ap）测量技术具有良好的相关性（r >= 0.95）。由于后向散射和多次散射的吸收增强，在相似波长下，未调整的Aethalometer（AE）和颗粒烟尘吸收光度计（PSAP）B（ap）比PA B（ap）高7倍。应用已发表的算法来校正这些效应，在532 nm处，AE和PSAP的差异分别降低至24%和17%。考虑后向散射效应的多角度吸收光度计（MAAP）相对于PA高估了B（ap）51%。由AE、MAAP和Sunset实验室半连续碳分析仪测定的BC浓度也高度相关（r >= 0.93），但差异高达57%。EC测量与IMPROVE/EQUIPMENT热/光学协议，和法国两步热协议同意在29%以内。根据PA B（ap）和EC测定的吸收效率（采用不同分析方案测量）平均为7.9 +/- 1.5。5.4+/- 1.1和2.8 +/- 0.6 m（2）/g。根据调整后的AE和PA B（ap）确定的Angstrom指数（α）范围为1.19至1.46。最大值的α发生在下午的时候，总碳的有机部分是最高的。与基于过滤器的B（ap）、BC和EC测量相关的显著偏倚具有方法特异性。校正这些偏差必须考虑到气溶胶浓度、成分和来源的差异。(C)2009爱思唯尔有限公司版权所有。
Particle light absorption (b(ap)), black carbon (BC), and elemental carbon (EC) measurements at the Fresno Supersite during the summer of 2005 were compared to examine the equivalency of current techniques, evaluate filter-based b(ap) correction methods, and determine the EC mass absorption efficiency (sigma(ap)) and the spectral dependence of b(ap). The photoacoustic analyzer (PA) was used as a benchmark for in-situ b(ap). Most b(ap) measurement techniques were well correlated (r >= 0.95). Unadjusted Aethalometer (AE) and Particle Soot Absorption Photometer (PSAP) b(ap) were up to seven times higher than PA b(ap) at Similar wavelengths because of absorption enhancement by backscattering and multiple scattering. Applying published algorithms to Correct for these effects reduced the differences to 24 and 17% for the AE and PSAP, respectively, at 532 nm. The Multi-Angle Absorption Photometer (MAAP), which accounts for backscattering effects, overestimated b(ap) relative to the PA by 51%. BC concentrations determined by the AE, MAAP, and Sunset Laboratory semi-continuous carbon analyzer were also highly correlated (r >= 0.93) but differed by up to 57%. EC measured with the IMPROVE/STN thermal/optical protocols, and the French two-step thermal protocol agreed to within 29%. Absorption efficiencies determined from PA b(ap) and EC measured with different analytical protocols averaged 7.9 +/- 1.5. 5.4 +/- 1.1, and 2.8 +/- 0.6 m(2)/g at 532, 670, and 1047 nm, respectively. The Angstrom exponent (alpha) determined from adjusted AE and PA b(ap) ranged from 1.19 to 1.46. The largest values of alpha occurred during the afternoon hours when the organic fraction of total carbon was highest. Significant biases associated with filter-based measurements of b(ap), BC, and EC are method-specific. Correcting for these biases must take into account differences in aerosol concentration, composition, and sources. (C) 2009 Elsevier B.V. All rights reserved.