Carbonaceous aerosol AAE inferred from in-situ aerosol measurements at the Gosan ABC super site, and the implications for brown carbon aerosol

Chung, Chien; Kim, S.-W.; Lee, Myeongsang; Yoon, Soon‐Chang; Lee, S.

doi:10.5194/acp-12-6173-2012

Cited by 64 publications

(46 citation statements)

References 41 publications

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“…Observations over California indicate that BrC absorption is 20-40% that of measured elemental carbon (Bahadur et al, 2012;Chung et al, 2012), which peaks in summer with SOA production and forest fire frequency (Bahadur et al, 2012). Smog chamber experiments indicate that BrC from biomass burning depends mainly on burn conditions, and can be parameterized as a function of BC to organic aerosol ratios (Saleh et al, 2014).…”

Section: Black Carbon (Bc)mentioning

confidence: 99%

Air Quality and Climate Connections

Fiore

Naik

Leibensperger

2015

Journal of the Air & Waste Management Association

384

292

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Multiple linkages connect air quality and climate change. Many air pollutant sources also emit carbon dioxide (CO 2 ), the dominant anthropogenic greenhouse gas (GHG). The two main contributors to non-attainment of U.S. ambient air quality standards, ozone (O 3 ) and particulate matter (PM), interact with radiation, forcing climate change. PM warms by absorbing sunlight (e.g., black carbon) or cools by scattering sunlight (e.g., sulfates) and interacts with clouds; these radiative and microphysical interactions can induce changes in precipitation and regional circulation patterns. Climate change is expected to degrade air quality in many polluted regions by changing air pollution meteorology (ventilation and dilution), precipitation and other removal processes, and by triggering some amplifying responses in atmospheric chemistry and in anthropogenic and natural sources. Together, these processes shape distributions and extreme episodes of O 3 and PM. Global modeling indicates that as air pollution programs reduce SO 2 to meet health and other air quality goals, near-term warming accelerates due to "unmasking" of warming induced by rising CO 2 . Air pollutant controls on CH 4 , a potent GHG and precursor to global O 3 levels, and on sources with high black carbon (BC) to organic carbon (OC) ratios could offset near-term warming induced by SO 2 emission reductions, while reducing global background O 3 and regionally high levels of PM. Lowering peak warming requires decreasing atmospheric CO 2 , which for some source categories would also reduce co-emitted air pollutants or their precursors. Model projections for alternative climate and air quality scenarios indicate a wide range for U.S. surface O 3 and fine PM, although regional projections may be confounded by interannual to decadal natural climate variability. Continued implementation of U.S. NO x emission controls guards against rising pollution levels triggered either by climate change or by global emission growth. Improved accuracy and trends in emission inventories are critical for accountability analyses of historical and projected air pollution and climate mitigation policies.Implications: The expansion of U.S. air pollution policy to protect climate provides an opportunity for joint mitigation, with CH 4 a prime target. BC reductions in developing nations would lower the global health burden, and for BC-rich sources (e.g., diesel) may lessen warming. Controls on these emissions could offset near-term warming induced by health-motivated reductions of sulfate (cooling). Wildfires, dust, and other natural PM and O 3 sources may increase with climate warming, posing challenges to implementing and attaining air quality standards. Accountability analyses for recent and projected air pollution and climate control strategies should underpin estimated benefits and trade-offs of future policies.

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Section: Black Carbon (Bc)mentioning

confidence: 99%

Air Quality and Climate Connections

Fiore

Naik

Leibensperger

2015

Journal of the Air & Waste Management Association

384

292

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“…However retrievals and subsequent data products can be subject to significant uncertainty that is difficult to quantify (Li et al, 2009). Here we focus on the simple AAE approach on account of its widespread use in peer-reviewed studies (Bahadur et al, 2012;Cazorla et al, 2013;Chung et al, 2012;Clarke et al, 2007;Esposito et al, 2012;Favez et al, 2009;Fialho et al, 2005;Gadhavi and Jayaraman, 2010;Herich et al, 2011;McNaughton et al, 2011;Sandradewi et al, 2008a, b;Wang et al, 2013;Yang et al, 2009). …”

Section: Methodsmentioning

confidence: 99%

On the attribution of black and brown carbon light absorption using the Ångström exponent

2013

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Abstract. The absorption Ångström exponent (AAE) of externally mixed black carbon (BC Ext ), or BC internally mixed with non-absorbing material (BC Int ), is often used to determine the contribution of brown carbon (BrC) light absorption at short visible wavelengths. This attribution method contains assumptions with uncertainties that have not been formally assessed. We show that the potential range of AAE for BC Ext (or BC Int ) in the atmosphere can reasonably lead to +7 % to −22 % uncertainty in BC Ext (or BC Int ) absorption at short wavelengths derived from measurements made at longer wavelengths, where BrC is assumed not to absorb light. These uncertainties propagate to errors in the attributed absorption of BrC. For uncertainty in attributed BrC absorption to be ≤ ± 33 %, 23 % to 41 % of total absorption must be sourced from BrC. These uncertainties would be larger if absorption by dust were also to be considered due to additional AAE assumptions. For data collected during a biomass-burning event, the mean difference between measured and AAE attributed BrC absorption was found to be 34 % -an additional uncertainty in addition to the theoretical uncertainties presented. In light of the potential for introducing significant and poorly constrained errors, we caution against the universal application of the AAE method for attributing BrC absorption.

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“…The value of α ap was mostly reported close to or higher than the unit for ambient aerosol because of the existence of other light absorbing species besides BC, such as brown carbon (BrC) 5 -2 7 5 -2 9 5 -3 1 6 -2 6 -4 6 -6 6 -8 6 -1 0 6 -1 2 6 -1 4 6 -1 6 6 -1 8 6 -2 0 6 -2 2 6 -2 4 6 -2 6 6 -2 8 6 -3 0 and dust, which absorb stronger in shorter wavelength ranges (e.g., UV spectrum) (Andreae and Gelencsér, 2006;Bergstrom et al, 2007). Even BrC in eastern Asia outflow has been reported as absorbing highly at long wavelengths (e.g., visible and near-infrared spectrum), the α ap of which is also considered to be much higher than 1 (e.g., ~1.7 presented by Chung et al, 2012;~1.5 by Alexander et al, 2008). Therefore, lower α ap should not only be attributed to the coexistence of BrC or dust with BC, even though the ratio of organic OC to EC showed a significantly negative correlation with the α ap (R = -0.70, Fig.…”

Section: Wavelength Dependencementioning

confidence: 99%

Spectral Light Absorption of Ambient Aerosols in Urban Beijing during Summer: An Intercomparison of Measurements from a Range of Instruments

Yan

Tian

et al. 2015

Aerosol Air Qual. Res.

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Aerosol light absorption is important to radiation balance, but it is difficult to accurately quantify using measurements. An intercomparison experiment for the measurement of the aerosol absorption coefficient (b ap ) was performed at an urban site in Beijing during the summer of 2012, including the filter-based particle soot absorption photometer (PSAP) and aethalometer (AE-31), and the reference photoacoustic extinctiometer (PAX), CRDS-Neph (cavity-ring down spectroscopy/nephelometer) system, and multi-angle absorption photometer (MAAP). The CRDS-Neph system and PAX performed poorly due to unexpected reasons. The corrected b ap of the PSAP agreed well with the reference values determined by the MAAP, implying the applicability of this correction scheme as well as the credibility of the reference b ap of the MAAP. A new conversion factor with a value of ~7.1 ± 0.05 m 2 /g at ~530 nm was established by regressing the reference b ap against the AE-31 recorded black carbon (BC) concentrations, which is lower than the previously used value (8.28 m 2 /g). Accordingly, the absorption Ångström exponent (α ap ) was estimated as 0.85 ± 0.21 on average. It was ~1 on clean days but significantly lower during pollution episodes, implying the main contributor to aerosol light absorption is freshlyemitted BC on clean days but aged BC during pollution. BC core sizes and the coating are likely to have a great impact on the α ap , which needs further investigation. The mass absorption efficiency of BC was estimated by regressing the b ap against the filter-analyzed elemental carbon (EC) concentrations, resulting in a mean of 9.2 ± 0.5 m 2 /g at 670 nm. It was remarkably higher during pollution episodes than on clean days, implying a high variation of aerosol properties, such as the mixing state, with pollution levels.

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Carbonaceous aerosol AAE inferred from in-situ aerosol measurements at the Gosan ABC super site, and the implications for brown carbon aerosol

Cited by 64 publications

References 41 publications

Air Quality and Climate Connections

Air Quality and Climate Connections

On the attribution of black and brown carbon light absorption using the Ångström exponent

Spectral Light Absorption of Ambient Aerosols in Urban Beijing during Summer: An Intercomparison of Measurements from a Range of Instruments

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