气候变化领域集成服务门户(CCPortal): Measuring light absorption by freshly emitted organic aerosols: Optical artifacts in traditional solvent-extraction-based methods

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DOI	10.5194/acp-19-8817-2019
	Measuring light absorption by freshly emitted organic aerosols: Optical artifacts in traditional solvent-extraction-based methods
	Shetty N.J.; Pandey A.; Baker S.; Hao W.M.; Chakrabarty R.K.
发表日期	2019
ISSN	16807316
起始页码	8817
结束页码	8830
卷号	19 期号:13
英文摘要	Recent studies have shown that organic aerosol (OA) could have a nontrivial role in atmospheric light absorption at shorter visible wavelengths. Good estimates of OA light absorption are therefore necessary to better estimate radiative forcing due to these aerosols in climate models. One of the common techniques used to measure OA light absorption is the solvent extraction technique from filter samples which involves the use of a spectrophotometer to measure bulk absorbance by the solvent-soluble organic fraction of particulate matter. Measured solvent-phase absorbance is subsequently converted to particle-phase absorption coefficient using scaling factors. The conventional view is to apply a correction factor of 2 to absorption coefficients obtained from solvent-extracted OA based on Mie calculations. The appropriate scaling factors are a function of biases due to incomplete extraction of organic carbon (OC) by solvents and size-dependent absorption properties of OA. The range for these biases along with their potential dependence on burn conditions is an unexplored area of research. Here, we performed a comprehensive laboratory study involving three solvents (water, methanol, and acetone) to investigate the bias in absorption coefficients obtained from solvent-extraction-based photometry techniques as compared to in situ particle-phase absorption for freshly emitted OA from biomass burning. We correlated the bias with OC=TC (total carbon) mass ratio and single scattering albedo (SSA) and observed that the conventionally used correction factor of 2 for water and methanol-extracted OA might not be extensible to all systems, and we suggest caution while using such correction factors to estimate particle-phase OA absorption coefficients. Furthermore, a linear correlation between SSA and the OC=TC ratio was also established. Finally, from the spectroscopic data, we analyzed the differences in absorption Ångström exponents (AÅE) obtained from solutionand particulate-phase measurements. We noted that AÅE from solvent-phase measurements could deviate significantly from their OA counterparts. © 2019 Author(s). This work is distributed under the Creative Commons Attribution 4.0 License.
语种	英语
scopus关键词	absorption; aerosol; aerosol property; concentration (composition); extraction method; optical depth; solvent
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144289
作者单位	Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, United States; USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT, United States; McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, United States
推荐引用方式 GB/T 7714	Shetty N.J.,Pandey A.,Baker S.,et al. Measuring light absorption by freshly emitted organic aerosols: Optical artifacts in traditional solvent-extraction-based methods[J],2019,19(13).
APA	Shetty N.J.,Pandey A.,Baker S.,Hao W.M.,&Chakrabarty R.K..(2019).Measuring light absorption by freshly emitted organic aerosols: Optical artifacts in traditional solvent-extraction-based methods.Atmospheric Chemistry and Physics,19(13).
MLA	Shetty N.J.,et al."Measuring light absorption by freshly emitted organic aerosols: Optical artifacts in traditional solvent-extraction-based methods".Atmospheric Chemistry and Physics 19.13(2019).