美国沙漠研究所Judith C. Chow 教授团队特邀文章——PM2.5 中棕碳吸光效应估算的改进

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特邀文章

Available online 15 January 2021

Improved estimation of PM2.5 brown carbon contributions to filter light attenuation (Open Access)

Judith C. Chow, L.-W. Antony Chen, Xiaoliang Wang, Mark C. Green, John G. Watson

DOI: 10.1016/j.partic.2021.01.001

Keywords: Organic carbon, Brown carbon, Elemental carbon, Black carbon, Absorption Ångström Exponent

美国沙漠研究所Judith C. Chow 教授团队开发的多波段有机碳/元素碳分析方法自2016年起被美国颗粒物化学组分观测网（CSN network）以及能见度观测网（IMPROVE network）采用。该方法可推算PM_2.5中棕碳在不同波长下对光吸收系数的贡献，进而有效地将生物质燃烧产生的碳与其它碳源相区分。然而，基于滤膜的光衰减测量会由于颗粒物的遮蔽效应而使光吸收系数定量产生偏差。

近期，Judith C. Chow 教授团队在Particuology上发表了题为“Improved estimation of PM_2.5 brown carbon contributions to filter light attenuation”的研究论文，对上述方法进行了改进。该文章详细分析了美国城市和自然保护区近十万个滤膜样品的数据，总结了滤膜光衰减和吸光颗粒物载荷的关系，对载荷效应进行了修正；同时通过对每个样品在635–780 nm波长的吸收来测量黑碳Ångström指数（AAE）避免了不准确的黑碳AAE=1的假设，从而更准确地推算了棕碳的吸光效应。

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亮点·导读

# Multiwavelength thermal/optical carbon analysis permits brown carbon estimates.

# Light attenuation deviates from Beer's Law at loadings greater than 3 μg/cm².

# Filter loading correction factor increase as wavelength decreases for a given elemental carbon filter loading.

# The conventional assumption that the black carbon Absorption Ångström Exponent equals one is not confirmed by multiwavelength measurements.

研究·背景

碳气溶胶是大气气溶胶的重要组分，它通常根据化学成分可以分为有机碳(OC)和元素碳（EC）或者根据光学性质分为黑碳 （BC），棕碳 (BrC)，和不吸光碳。棕碳是对紫外和可见光波段有吸收效应的有机碳，因为其广泛的排放和对辐射强迫、大气能见度和光化学反应的重要影响而被关注。然而，目前对于棕碳的基础研究刚刚起步，对于它的来源、排放、组成、演变及光学化学性质的认识还十分有限。

美国沙漠研究所的Judith C. Chow 教授团队开发了多波段有机碳/元素碳分析仪，该仪器在用热光法进行常规的有机碳和元素碳分析的基础上增加了从近紫外到红外（405–980 nm）的多波段光衰减测量，从而推算棕碳和黑碳对光吸收系数的贡献。然而，基于滤膜的光衰减测量会由于颗粒物的遮蔽效应而使光吸收系数定量产生偏差。

内容·简介

本文详细分析了美国位于城市地区的颗粒物化学组分观测网（CSN network；2016–2017）和位于国家自然保护区的能见度观测网（IMPROVE network；2016–2019）近十万个滤膜样品的数据，总结了光衰减和吸光颗粒物载荷的关系，从而对载荷效应进行了修正。本文还指出通常假设的黑碳吸收Ångström指数（AAE）为1不准确并可能因此低估棕碳对光吸收系数的贡献。从635–780 nm波长分析的数据显示CSN 和IMPROVE 黑碳的AAE中位值分别为0.76和0.80。本文强调在元素碳浓度超过1.5 µg/m³时有必要对载荷效应进行修正并使用实际测量得到的黑碳AAE，从而推算棕碳及黑碳对光吸收系数的准确贡献。

作者·介绍

Judith C. Chow

研究方向：空气质量、大气观测、碳气溶胶、颗粒物分析、健康效应等

Dr. Judith C. Chow is a Research Professor in the Division of Atmospheric Sciences at the Desert Research Institute (DRI), Nevada System of Higher Education. She is the founder and director of DRI's Environmental Analysis Facility and led the development of three generations of thermal/optical carbon analyzers. Dr. Chow has served on many monitoring and research advisory committees for air quality, including the National Academy of Sciences/National Research Council Committee on "Research Priorities for Airborne Particulate Matter". She was a chartered member of the U.S. EPA's Clean Air Scientific Advisory Committee (CASAC) and a member of U.S. EPA's Ambient Air Monitoring and Methods Subcommittee (now the Air Monitoring and Methods Subcommittee). She authored more than 400 journal articles with a h-index of 79. Dr. Chow obtained her Sc.D. in Environmental Science and Physiology from Harvard University.

L.-W. Antony Chen

 (陳隆文)

研究方向：空气污染，源解析及风险评估

Dr. Antony Chen is an associate professor in the Department of Environmental and Occupational Health at the School of Public Health, University of Nevada, Las Vegas. Dr. Chen researches atmospheric aerosols and co-pollutants from natural and anthropogenic sources, focusing on development of monitoring and modeling methods for assessing public exposure and health risks. He has ~100 peer-reviewed publications with an h index of 36. Dr. Chen leads the UNLV Urban Air Quality Laboratory and teaches Air Pollution, Atmospheric Measurement and Modeling, and Environmental Health courses at both graduate and undergraduate levels. Dr. Chen obtained his Ph.D. in Chemical Physics-Atmospheric Chemistry from the University of Maryland and worked at Desert Research Institute for 10 years prior to joining UNLV. 

Xiaoliang Wang 

(王小亮)

研究方向：气溶胶物理化学性质表征、测量仪器开发、污染源排放测量等

Dr. Xiaoliang Wang is a Research Professor in DRI's Division of Atmospheric Sciences. He has been involved in the development of an array of instruments for characterizing aerosol properties, including nanoparticle aerodynamic lenses, the TSI DustTrak DRX Aerosol Monitor, the DRI portable dilution sampling system, and the DRI Model 2015 Multiwavelength Thermal/Optical Carbon Analyzer. He is the recipient of the 2020 Benjamin Y.H. Liu Award from the American Association for Aerosol Research (AAAR), for his outstanding contributions to aerosol instrumentation and experimental techniques. Dr. Wang obtained his Ph.D. in Mechanical Engineering from University of Minnesota and is a graduate of the Thermal and Environmental Engineering Departments at Tsinghua University. He worked for 4 years at TSI Inc. before joining DRI. 

Mark C. Green

研究方向：空气污染、雾霾和能见度观测、气象观测和分析等

Dr. Green is a Research Professor in DRI's Division of Atmospheric Sciences. He has over 30 years' experience in the fields of air pollution and meteorology with research focuses on determining the causes of haze in both remote and urban areas and the attribution of suspended particles to emission sources. Dr. Green obtained his Ph.D. in Atmospheric Science from University of California at Davis.

John G. Watson

研究方向：颗粒物源解析、空气质量和能见度观测、污染源表征、低成本传感器等

Dr. John G. Watson is a Research Professor in DRI's Division of Atmospheric Sciences. He developed the U.S. EPA's Chemical Mass Balance receptor modeling software and has prepared  guidance documents for network design, continuous particulate monitoring, and pollutant chemical speciation. He has designed and led dozens of major aerosol and visibility characterization studies. Dr. Watson has authored more than 400 peer-reviewed journal publications with a h-index of 74, including the Air & Waste Management Association (A&WMA) 2002 critical review on "Visibility: Science and Regulation" and  the 2017 critical review on "Air quality measurements—From rubber bands to tapping the rainbow". Dr. Watson obtained his Ph.D. in Environmental Sciences from Oregon Graduate Institute, now the Oregon Health and Science University. 

PARTICUOLOGY简介

Particuology(《颗粒学报》)是由中国科协主管，中国颗粒学会和中国科学院过程工程研究所主办，科学出版社和Elsevier出版集团共同出版的英文版双月刊，正式创刊于2003年4月。首任主编为郭慕孙院士，现任主编为李静海院士。

Particuology2019年度影响因子2.787, 五年影响因子3.111，已连续十年分别在SCI化工类及材料综合类期刊中位列Q2区，是颗粒学领域三大期刊之一。同时，《颗粒学报》始终坚持以创精品与国际化为办刊方针，多年来一直保持60%国际稿源，70%国际审稿，作者来自中国、美国、德国、英国、澳大利亚等20多个国家，读者遍布全球100多个国家，并连续九年被评为“中国最具国际影响力期刊”称号。

Particuology主要刊登国内外颗粒学领域在研究、工程和应用方面的优秀原创论文，内容涉及颗粒测试与表征、颗粒制备与处理、流态化与颗粒流系统、固体散料技术、模拟与仿真技术、气溶胶科学与技术、材料科学与工程、纳米颗粒、能源颗粒、生物颗粒与仿生技术等领域。热忱欢迎国内外相关领域专家、学者、研究人员来稿！

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