Photoacoustic and filter‐based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity

Arnott, W. P.; Moosmüller, Hans; Sheridan, Patrick J.; Ogren, J. A.; Raspet, Richard; Slaton, William V.; Hand, Jenny L.; Kreidenweis, Sonia M.; Collett, Jeffrey L.

doi:10.1029/2002jd002165

Cited by 204 publications

(213 citation statements)

References 43 publications

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“…An average value of σ (λ) = 10.4±2.0 m 2 g −1 was obtained and used to calculate the EBC presented in this work. Absorption cross sections between 7 m 2 g −1 and 11 m 2 g −1 are usually reported in literature (see for example Bond and Bergstrom, 2006;Fernández-Camacho et al, 2010;He et al, 2009;Barnard et al, 2008;Arnott et al, 2003Arnott et al, , 2005Reche et al, 2011)). …”

Section: Data Processingmentioning

confidence: 99%

Variability of aerosol optical properties in the Western Mediterranean Basin

et al. 2011

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Abstract. Aerosol light scattering, absorption and particulate matter (PM) concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB) which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Mean scattering and hemispheric backscattering coefficients (@ 635 nm) were 26.6±23.2 Mm −1 and 4.3±2.7 Mm −1 , respectively and the mean aerosol absorption coefficient (@ 637 nm) was 2.8±2.2 Mm −1 . Mean values of Single Scattering Albedo (SSA) andÅngström exponent (å) (calculated from 450 nm to 635 nm) at MSY were 0.90±0.05 and 1.3±0.5 respectively. A clear relationship was observed between the PM 1 /PM 10 and PM 2.5 /PM 10 ratios as a function of the calculatedÅngström exponents. Mass scattering cross sections (MSC) for fine mass and sulfate at 635 nm were 2.8±0.5 m 2 g −1 and 11.8±2.2 m 2 g −1 , respectively, while the mean aerosol absorption cross section (MAC) was 10.4±2.0 m 2 g −1 . The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The MAC values appear dependent of particles aging: similar to the expected absorption cross-section for fresh emissions under Atlantic Advection episodes and higher under aerosol pollution episodes. The analysis of theÅngström exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (å = 1.5±0.1) while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly dominated by coarser particles (å = 1.0±0.4). The sea breeze played an important role Correspondence to: M. Pandolfi (marco.pandolfi@idaea.csic.es) in transporting pollutants from the developed WMB coastlines towards inland rural areas, changing the optical properties of aerosols. Aerosol scattering and backscattering coefficients increased by around 40 % in the afternoon when the sea breeze was fully developed while the absorption coefficient increased by more than 100 % as a consequence of the increase in the equivalent black carbon concentration (EBC) observed at MSY under sea breeze circulation.

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Section: Data Processingmentioning

confidence: 99%

Variability of aerosol optical properties in the Western Mediterranean Basin

et al. 2011

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“…On the other hand, laboratory comparisons between the PAS and difference method suggest that the PAS can determine aerosol absorption with an accuracy <10% (Moosmüller et al, 1998;Arnott et al, 1999;Arnott et al, 2003;Sheridan et al, 2005).…”

Section: Problems Related To the Measurement Of Aerosol Light Absorptionmentioning

confidence: 99%

“…Comparisons of simultaneous measurements made using PAS and filter-based techniques (PSAP, aethalometer, integrating plate) show considerable differences (up to a factor of two) under some circumstances, especially when the relative humidity is variable (Moosmüller et al, 1998;Arnott et al, 1999;Arnott et al, 2003;Sheridan et al, 2005). The most reliable filter-based instrument for absorption measurements at this time is the multi-angle absorption photometer (MAAP), which simultaneously measures transmittance and reflectance of the filter at multiple angles and uses a twostream radiative transfer model to determine the filter and aerosol scattering corrections for the absorption measurement (Petzold and Schönlinner, 2004).…”

Section: Problems Related To the Measurement Of Aerosol Light Absorptionmentioning

confidence: 99%

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

Andreae

Gelencsér²

2006

Atmos. Chem. Phys.

1,789

1,033

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Abstract. Although the definition and measurement techniques for atmospheric "black carbon" ("BC") or "elemental carbon'' ("EC") have long been subjects of scientific controversy, the recent discovery of light-absorbing carbon that is not black ("brown carbon, Cbrown") makes it imperative to reassess and redefine the components that make up light-absorbing carbonaceous matter (LAC) in the atmosphere. Evidence for the atmospheric presence of Cbrown comes from (1) spectral aerosol light absorption measurements near specific combustion sources, (2) observations of spectral properties of water extracts of continental aerosol, (3) laboratory studies indicating the formation of light-absorbing organic matter in the atmosphere, and (4) indirectly from the chemical analogy of aerosol species to colored natural humic substances. We show that brown carbon may severely bias measurements of "BC" and "EC" over vast parts of the troposphere, especially those strongly polluted by biomass burning, where the mass concentration of Cbrown is high relative to that of soot carbon. Chemical measurements to determine "EC" are biased by the refractory nature of Cbrown as well as by complex matrix interferences. Optical measurements of "BC" suffer from a number of problems: (1) many of the presently used instruments introduce a substantial bias into the determination of aerosol light absorption, (2) there is no unique conversion factor between light absorption and "EC" or "BC" concentration in ambient aerosols, and (3) the difference in spectral properties between the different types of LAC, as well as the chemical complexity of Cbrown, lead to several conceptual as well as practical complications. We also suggest that due to the sharply increasing absorption of Cbrown towards the UV, single-wavelength light absorption measurements may not be adequate for the assessment of absorption of solar radiation in the troposphere. We discuss the possible consequences of these effects for our understanding of tropospheric processes, including their influence on UV-irradiance, atmospheric photochemistry and radiative transfer in clouds.

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“…10 m 2 g often used for urban aerosols (Moosmuller, 1998), 8-10 m 2 g (at 550 nm) in Mexico City (Barnard, 2005), 8.5 m 2 g from BRAVO (Big Bend Regional Aerosol and Visibility Observation Study) (Arnott, 2003). The conversion factor 8.28 m 2 g was also used in a study by Yan et al (2008) for obtaining the aerosol absorption over a rural site in North China.…”

Section: Measurements and Instrumentationsmentioning

confidence: 99%

An intensive study of aerosol optical properties in Beijing urban area

Lau

et al. 2009

Atmos. Chem. Phys.

120

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Abstract. In order to quantify the aerosol impact on climate, a range of aerosol parameters are required. In this paper, twoyear of ground-based observations of aerosol optical properties from an urban site in Beijing of China are assessed. The aerosol absorption coefficient (σ a ), scattering coefficient (σ s ), as well as single scattering albedo (ω) are analyzed to aid in characterizing Beijing's urban aerosol. Two-year averages (and standard deviations) for σ a at 532 nm, σ s at 525 nm and ω at 525 nm are 56±49 Mm −1 , 288±281 Mm −1 and 0.80±0.09, respectively. Meanwhile, there is a distinct diurnal variation for σ a , with its minimum occurring at approximately 14:00 to 15:00 and maximum at midnight. σ s peaks in the late morning and the minimum occurs in the evening. σ s in summer is higher than that in winter. ω is also higher in summer than that in winter, except before 07:00 a.m., and peaks in the early afternoon. Both σ a and σ s show strong dependence on local wind in all four seasons. When the wind blows from the north with low speed (0-2 m/s), the values of σ a are high, and in contrast, very low with wind speeds higher than 4 m/s. When the wind blows from south with low speed (0-4 m/s), σ a is intermediate. The patterns of the wind dependence of σ a indicates that σ a is mainly dominated by local emissions. σ s displays a similar dependence on wind speed and direction to σ a , except in summer. In summer, the σ s value is highest when wind is from southeast with speed of 0-6 m/s. This indicates that the particle pollution resulting from regional transport is only significant in the summer season. ω also shows wind dependence to some extent though not as strong as σ a or σ s . Overall, the wind dependence results provide valuable information about the locations of Correspondence to: C. C. Li (ccli@pku.edu.cn) aerosol pollution sources and suggest that the air pollution in summer is a regional problem but in other seasons it is mainly affected by local urban emissions.

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Photoacoustic and filter‐based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity

Cited by 204 publications

References 43 publications

Variability of aerosol optical properties in the Western Mediterranean Basin

Variability of aerosol optical properties in the Western Mediterranean Basin

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

An intensive study of aerosol optical properties in Beijing urban area

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