Brownness of organics in aerosols from biomass burning linked to their black carbon content

Saleh, Rawad; Robinson, Elmer; Tkacik, Daniel S.; Ahern, Adam; Liu, Shang; Aiken, A. C.; Sullivan, R. C.; Presto, Albert A.; Dubey, Manvendra K.; Yokelson, Robert J.; Donahue, Neil M.; Robinson, Allen L.

doi:10.1038/ngeo2220

Cited by 505 publications

(778 citation statements)

References 30 publications

(22 reference statements)

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“…We have found a trend where å abs increases with decreasing BC to OA mass ratio following an exponential function. These results are comparable to those presented by Pokhrel et al (2016) and Saleh et al (2014), with slightly lower å abs values in our study, however. This pattern could be related to a dominant presence of primary organic aerosol (POA) that has characteristically lower absorption wavelength dependence compared to SOA (Saleh et al, 2013).…”

Section: Absorption Wavelength Dependence and Brc Contributionsupporting

confidence: 76%

“…The ratio BC to OA has been used before to parameterize å abs and ω 0 (Pokhrel et al, 2016;Saleh et al, 2014) to OA mass ratio during the North African LRT events in the wet season can be found in Fig. 11.…”

Section: Absorption Wavelength Dependence and Brc Contributionmentioning

confidence: 99%

“…In case of condensation of non-BC material on the BC particles, the MAC can be enhanced due to the well-known 'lensing effect' (Fuller et al, 1999). This commonly happens when BC is emitted by BB, since it is co-emitted with large amounts of organic vapors that would condense on BC particles (Saleh et al, 2014). Black carbon particles can also obtain a secondary organic aerosol (SOA) coating during advection over the rain forest as well as inorganic coatings, which has been previously observed at the ATTO site (Pöhlker et al, 2014).…”

mentioning

confidence: 99%

“…However, it depends on the burning conditions, its BC to OA ratio (Saleh et al, 2014), and the BC-BrC size distributions and morphologies (Womack et al, ref needed). Several studies have used the absorption spectral dependence to apportion the fossil fuel and BB contributions to total absorption (Favez et al, 2010;Massabò et al, 2015;Sandradewi et al, 2008).…”

mentioning

confidence: 99%

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Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

Saturno¹,

Holanda²,

Pöhlker³

et al. 2017

Preprint

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Abstract. The Amazon rain forest is considered a very sensitive ecosystem that could be significantly affected by a changing climate. It is still one of the few places on Earth where the atmosphere in the continent approaches near-pristine conditions for some periods of the year. The Amazon Tall Tower Observatory (ATTO) has been built in central Amazonia to monitor the atmospheric and forest ecosystem conditions. The atmospheric conditions at the ATTO site oscillate between biogenic and biomass burning (BB) dominated states. By using a comprehensive ground-based aerosol measurement setup, we studied the physical and chemical properties of aerosol particles at the ATTO site. This parameterization of å abs as a function of the BC to OA mass ratio was investigated and was found applicable to tropical forest emissions but further investigation is required, especially by segregating fuel types. Additionally, important enhancements of the BC mass absorption cross-section (α abs ) were found over the measurement period. This enhancement could be linked to heavy coating of the BC aerosol particles. In the future, the BC mixing state should be systematically investigated by using different instrumental approaches.

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Section: Absorption Wavelength Dependence and Brc Contributionsupporting

confidence: 76%

Section: Absorption Wavelength Dependence and Brc Contributionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

Saturno¹,

Holanda²,

Pöhlker³

et al. 2017

Preprint

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“…Some difficulties still exist in predicting OA absorption in general, and even more in the case of biomass-burning OA due to its complex nature (41,42). However, recent laboratory results indicate that optical properties of biomass combustion aerosol can be successfully parameterized based on the BC-to-OA ratio (41). Fig.…”

Section: Discussionmentioning

confidence: 99%

Direct observation of aqueous secondary organic aerosol from biomass-burning emissions

Gilardoni

Massoli

Paglione

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

306

275

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The mechanisms leading to the formation of secondary organic aerosol (SOA) are an important subject of ongoing research for both air quality and climate. Recent laboratory experiments suggest that reactions taking place in the atmospheric liquid phase represent a potentially significant source of SOA mass. Here, we report direct ambient observations of SOA mass formation from processing of biomass-burning emissions in the aqueous phase. Aqueous SOA (aqSOA) formation is observed both in fog water and in wet aerosol. The aqSOA from biomass burning contributes to the "brown" carbon (BrC) budget and exhibits light absorption wavelength dependence close to the upper bound of the values observed in laboratory experiments for fresh and processed biomass-burning emissions. We estimate that the aqSOA from residential wood combustion can account for up to 0.1-0.5 Tg of organic aerosol (OA) per y in Europe, equivalent to 4-20% of the total OA emissions. Our findings highlight the importance of aqSOA from anthropogenic emissions on air quality and climate.particulate matter | air quality | secondary organic aerosol | biomass burning | aqueous processing

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The effect of complex black carbon microphysics on the determination of the optical properties of brown carbon

Liu

Taylor

Young

et al. 2015

Geophysical Research Letters

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Assessment of the impacts of brown carbon (BrC) requires accurate determination of its physicalproperties, but a model must be invoked to derive these from instrument data. Ambient measurements were made in London at a site influenced by traffic and solid fuel (principally wood) burning, apportioned by single particle soot photometer data and optical properties measured using multiwavelength photoacoustic spectroscopy. Two models were applied: a commonly used Mie model treating the particles as single-coated spheres and a Rayleigh-Debye-Gans approximation treating them as aggregates of smaller-coated monomers. The derived solid fuel BrC parameters at 405 nm were found to be highly sensitive to the model treatment, with a mass absorption cross section ranging from 0.47 to 1.81 m 2 /g and imaginary refractive index from 0.013 to 0.062. This demonstrates that a detailed knowledge of particle morphology must be obtained and invoked to accurately parameterize BrC properties based on aerosol phase measurements. BackgroundOptically absorbing soot in the atmosphere is characterized as being composed of a mixture of black carbon (BC) [Bond et al., 2013] and brown carbon (BrC) [Andreae and Gelencsér, 2006]. These are both important to the radiative properties of the atmosphere but have different wavelength-dependent characteristics. Attempts to model the effect of BC and BrC are hindered by uncertainties in their fundamental properties. A key parameter governing the effect of BrC is the imaginary part (k BrC ) of the refractive index at short wavelengths, and a large range of values have been derived through field and laboratory studies, resulting in uncertainty surrounding its impacts [Wang et al., 2014]. The absorption of brown carbon (σ abs,BrC ) from a variety of biomass burning sources has been assessed recently [e.g., Lack et al., 2012;Saleh et al., 2014] by subtracting the black carbon absorption (σ abs,BC ) from the total measured absorption (σ abs,total ). The explicit calculation of σ abs,BC is crucial for deriving σ abs,BrC , and therefore its mass absorption cross section (MAC) and k BrC . Therefore, the accuracy of the derived BrC parameters depends on the accuracy by which the BC properties can be estimated, which requires the invocation of an optical model treatment of the measured physical properties of the BC.Mie-based models [Bohren and Huffman, 1983] has been widely used to model the absorption properties of particles by treating them as concentric spheres; however, this model may not apply for BC particles close to source regions as they often more resemble aggregates of many small monomers [e.g., Xiong and Friedlander, 2001;China et al., 2013]. These aggregates can be described [Filippov et al., 2000] by using parameters such as the fractal dimension (D f ), monomer diameter (D s ), and number of monomers (N s ), which forms the basis for a number of advanced models considering particle morphology, such as superposition T-matrix [Mishchenko et al., 2013] and discrete dipole [Adachi et al., 20...

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Brownness of organics in aerosols from biomass burning linked to their black carbon content

Cited by 505 publications

References 30 publications

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

Direct observation of aqueous secondary organic aerosol from biomass-burning emissions

The effect of complex black carbon microphysics on the determination of the optical properties of brown carbon

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