Aircraft Instrument for Comprehensive Characterization of Aerosol Optical Properties, Part 2: Black and Brown Carbon Absorption and Absorption Enhancement Measured with Photo Acoustic Spectroscopy

Lack, D. A.; Richardson, M.; Law, D. C.; Langridge, Justin M.; Cappa, C. D.; McLaughlin, Richard J.; Murphy, D. M.

doi:10.1080/02786826.2011.645955

Cited by 145 publications

(207 citation statements)

References 53 publications

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“…Photoacoustic spectroscopy (PAS) has become a popular technique for measuring absorption of light by atmospheric aerosols for PAS (Lack et al, 2006(Lack et al, , 2012, recent works exploring its validity have come to contradictory conclusions: Bluvshtein et al (2017) saw a discrepancy between ozone calibrations and particle-based calibrations, while Davies et al (2018) found this not to be the case. Concurrent to these publications, we have been exploring the use of ozone as a PAS calibrant for multipass, multi-wavelength, aerosol photoacoustic spectrometers; our observations are presented here to add to the discussion on the topic.…”

Section: Introductionmentioning

confidence: 96%

“…By using multiple concentrations (or sizes, in the case of aerosols), a linear regression of s vs. b abs can be performed from which the slope, m, can be determined. Examples of calibrants include aerosol particles such as flame-generated soot (Arnott et al, 2000) and gas-phase absorbers such as ozone (Lack et al, 2006(Lack et al, , 2012 or nitrogen 20 dioxide (Arnott et al, 2000;Lewis et al, 2008;Cross et al, 2010). Although ozone absorbs weakly in the UV-A and violet regions of the spectrum and is difficult to measure at those wavelengths, it has been employed for field calibrations because it can be easily generated using a UV lamp or corona discharge.…”

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confidence: 99%

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Technical Note: Can ozone be used to calibrate aerosol photoacoustic spectrometers?

Fischer

Smith

2018

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Abstract. Photoacoustic spectroscopy (PAS) has become a popular technique for measuring absorption of light by atmospheric aerosols in both the laboratory and in field campaigns. It has low detection limits, measures suspended aerosols, and is insensitive to scattering. But PAS requires rigorous calibration to be applied quantitatively. Often, a PAS instrument is either filled with a gas of known concentration and absorption cross section, such that the absorption in the cell can be calculated from the product of the two, or the absorption is measured independently with a technique such as cavity ringdown spectroscopy. Then, 5 the PAS signal can be regressed upon the known absorption to determine a calibration slope that reflects the sensitivity constant of the cell and microphone. Ozone has been used for calibrating PAS instruments due to its well-known UV-visible absorption spectrum and the ease with which it can be generated. However, it is known to photodissociate up to approximately 1120 nmpathway, which is likely to lead to inaccuracies in aerosol measurements. Two recent studies have investigated the use of O 3 for PAS calibration but have reached seemingly contradictory conclusions 10 with one finding that it results in a sensitivity that is a factor of two low and the other concluding that it is accurate. The present work is meant to add to this discussion by exploring the extent to which O 3 photodissociates in the PAS cell and the role that the identity of the bath gas plays in determining the PAS sensitivity. We find a 5% loss in PAS signal attributable to photodissociation at 532 nm in N 2 but no loss in a 5% mixture of O 2 in N 2 . Furthermore, we discovered a dramatic increase of more than a factor of two in the PAS sensitivity as we increased the O 2 fraction in the bath gas, which reached an asymptote near 15 100% O 2 that nearly matched the sensitivity measured with both NO 2 and nigrosin particles. We interpret this dependence with a kinetic model that suggests the reason for the observed results is a more efficient transfer of energy from excited O 3 to O 2 than to N 2 by a factor of 22-55 depending on excitation wavelength.

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Section: Introductionmentioning

confidence: 96%

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confidence: 99%

Technical Note: Can ozone be used to calibrate aerosol photoacoustic spectrometers?

Fischer

Smith

2018

Preprint

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“…at 365 and 405 nm, and contribute approximately 10 % at midvisible wavelengths, e.g. at 532 nm (Bahadur et al, 2012;Lack et al, 2012b;Washenfelder et al, 2015;Nakayama et al, 2014). During an agricultural waste burning event, BrC aerosol could contribute more than 65 % of light absorption at 370 nm and 15 % at a mid-wavelength (Favez et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Light absorption of brown carbon aerosol in the PRD region of China

et al. 2016

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Abstract. The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method has been widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosols, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the AAE method was applied to both urban and rural environments in the Pearl River Delta (PRD) region of China, with an improvement of constraining the realistic AAE of "pure" BC through statistical analysis of on-line measurement data. A threewavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that more realistic AAE values for "pure" BC aerosol (AAE BC ) were 0.86, 0.82, and 1.02 between 405 and 781 nm, and 0.70, 0.71, and 0.86 between 532 and 781 nm, in the campaigns of urban winter , urban fall , and rural fall , respectively. Roadway tunnel experiments were conducted and the results further confirmed the representativeness of the obtained AAE BC values for the urban environment. Finally, the average light absorption contributions of BrC (± relative uncertainties) at 405 nm were quantified to be 11.7 % (±5 %), 6.3 % (±4 %), and 12.1 % (±7 %) in the campaigns of urban winter , urban fall , and rural fall , respectively, and those at 532 nm were 10.0 % (±2 %), 4.1 % (±3 %), and 5.5 % (±5 %), respectively. The relatively higher BrC absorption contribution at 405 nm in the rural fall campaign could be reasonably attributed to the biomass burning events nearby, which was then directly supported by the biomass burning simulation experiments performed in this study. This paper indicates that the BrC contribution to total aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region.

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“…Cavity ring-down extinction: the b ext measurements at 405 and 532 nm were made using the UC Davis (UCD) twowavelength cavity ring-down photoacoustic spectrometer (CRD-PAS) instrument (Langridge et al, 2011;Lack et al, 2012). Full details of these measurements are available in Cappa et al (2016) and Atkinson et al (2015).…”

Section: Instruments Used At the T0 Site (American Rivermentioning

confidence: 99%

Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

et al. 2018

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Abstract. Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are analyzed using a spectral deconvolution method that allows extraction of particle-sizerelated information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved finemode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM 1 and PM 10 , although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of "fine" and "coarse" modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.

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Aircraft Instrument for Comprehensive Characterization of Aerosol Optical Properties, Part 2: Black and Brown Carbon Absorption and Absorption Enhancement Measured with Photo Acoustic Spectroscopy

Cited by 145 publications

References 53 publications

Technical Note: Can ozone be used to calibrate aerosol photoacoustic spectrometers?

Technical Note: Can ozone be used to calibrate aerosol photoacoustic spectrometers?

Light absorption of brown carbon aerosol in the PRD region of China

Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

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