Modeled source apportionment of black carbon particles coated with a light-scattering shell

Mapping Intimacies ◽

10.5194/amt-2020-438 ◽

2020 ◽

Author(s):

Aki Virkkula

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Fossil Fuel ◽

Size Distributions ◽

Core Size ◽

Carbon Particles ◽

Aerosol Mass ◽

Measured Absorption ◽

Absorbing Material ◽

Fossil Fuel Emissions

Abstract. The Aethalometer model been used widely for estimating the contributions of fossil fuel emissions and biomass burning to equivalent black carbon (eBC). The calculation is based on measured absorption Ångström exponents (αabs). The interpretation αabs is ambiguous since it is well-known that it not only depends on the dominant absorber but also on the size and internal structure of the particles, core size and shell thickness. In this work the uncertainties of the Aethalometer-model-derived apparent fractions of absorption by eBC from fossil fuel and biomass burning are evaluated with a core-shell Mie model. Biomass-burning fractions (BB(%)) were calculated for pure and coated single BC particles, for lognormal unimodal and bimodal size distributions of BC cores coated with ammonium sulfate, a scattering-only material. BB(%) was very seldom 0 % even though BC was the only absorbing material in the simulations. The shape of size distribution plays an important role. Narrow size distributions result in higher αabs and BB(%) values than wide size distributions. The sensitivity of αabs and BB(%) to variations in shell volume fractions is the highest for accumulation mode particles. This is important because that is where the largest aerosol mass is. For the interpretation of absorption Ångström exponents it would be very good to measure BC size distributions and shell thicknesses together with the wavelength dependency of absorption.

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Modeled source apportionment of black carbon particles coated with a light-scattering shell

Atmospheric Measurement Techniques ◽

10.5194/amt-14-3707-2021 ◽

2021 ◽

Vol 14 (5) ◽

pp. 3707-3719

Author(s):

Aki Virkkula

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Fossil Fuel ◽

Size Distributions ◽

Core Size ◽

Carbon Particles ◽

Aerosol Mass ◽

Measured Absorption ◽

Absorbing Material ◽

Fossil Fuel Emissions

Abstract. The Aethalometer model has been used widely for estimating the contributions of fossil fuel emissions and biomass burning to equivalent black carbon (eBC). The calculation is based on measured absorption Ångström exponents (αabs). The interpretation of αabs is ambiguous since it is well known that it not only depends on the dominant absorber but also on the size and internal structure of the particles, core size, and shell thickness. In this work the uncertainties of the Aethalometer-model-derived apparent fractions of absorption by eBC from fossil fuel and biomass burning are evaluated with a core–shell Mie model. Biomass-burning fractions (BB(%)) were calculated for pure and coated single BC particles for lognormal unimodal and bimodal size distributions of BC cores coated with ammonium sulfate, a scattering-only material. BB(%) was very seldom 0 % even though BC was the only absorbing material in the simulations. The shape of size distribution plays an important role. Narrow size distributions result in higher αabs and BB(%) values than wide size distributions. The sensitivity of αabs and BB(%) to variations in shell volume fractions is the highest for accumulation-mode particles. This is important because that is where the largest aerosol mass is. For the interpretation of absorption Ångström exponents it would be very good to measure BC size distributions and shell thicknesses together with the wavelength dependency of absorption.

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The contribution of black carbon to global ice nucleating particle concentrations relevant to mixed-phase clouds

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2001674117 ◽

2020 ◽

Vol 117 (37) ◽

pp. 22705-22711

Author(s):

Gregory P. Schill ◽

Paul J. DeMott ◽

Ethan W. Emerson ◽

Anne Marie C. Rauker ◽

John K. Kodros ◽

...

Keyword(s):

Black Carbon ◽

Biomass Burning ◽

Fossil Fuel ◽

Supercooled Liquid ◽

Mixed Phase ◽

Radiative Properties ◽

Prescribed Burns ◽

Earth’S Climate ◽

Mixed Phase Clouds ◽

Fossil Fuel Emissions

Black carbon (BC) aerosol plays an important role in the Earth’s climate system because it absorbs solar radiation and therefore potentially warms the climate; however, BC can also act as a seed for cloud particles, which may offset much of its warming potential. If BC acts as an ice nucleating particle (INP), BC could affect the lifetime, albedo, and radiative properties of clouds containing both supercooled liquid water droplets and ice particles (mixed-phase clouds). Over 40% of global BC emissions are from biomass burning; however, the ability of biomass burning BC to act as an INP in mixed-phase cloud conditions is almost entirely unconstrained. To provide these observational constraints, we measured the contribution of BC to INP concentrations ([INP]) in real-world prescribed burns and wildfires. We found that BC contributes, at most, 10% to [INP] during these burns. From this, we developed a parameterization for biomass burning BC and combined it with a BC parameterization previously used for fossil fuel emissions. Applying these parameterizations to global model output, we find that the contribution of BC to potential [INP] relevant to mixed-phase clouds is ∼5% on a global average.

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Size distribution, mixing state and source apportionment of black carbon aerosol in London during wintertime

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-10061-2014 ◽

2014 ◽

Vol 14 (18) ◽

pp. 10061-10084 ◽

Cited By ~ 90

Author(s):

D. Liu ◽

J. D. Allan ◽

D. E. Young ◽

H. Coe ◽

D. Beddows ◽

...

Keyword(s):

Linear Regression ◽

Multiple Linear Regression ◽

Size Distribution ◽

Black Carbon ◽

Coating Thickness ◽

Urban Site ◽

Core Size ◽

Air Masses ◽

Aerosol Mass ◽

Mass Median

Abstract. Black carbon aerosols (BC) at a London urban site were characterised in both winter- and summertime 2012 during the Clean Air for London (ClearfLo) project. Positive matrix factorisation (PMF) factors of organic aerosol mass spectra measured by a high-resolution aerosol mass spectrometer (HR-AMS) showed traffic-dominant sources in summer but in winter the influence of additional non-traffic sources became more important, mainly from solid fuel sources (SF). Measurements using a single particle soot photometer (SP2, DMT), showed the traffic-dominant BC exhibited an almost uniform BC core size (Dc) distribution with very thin coating thickness throughout the detectable range of Dc. However, the size distribution of Dc (project average mass median Dc = 149 ± 22 nm in winter, and 120 ± 6 nm in summer) and BC coating thickness varied significantly in winter. A novel methodology was developed to attribute the BC number concentrations and mass abundances from traffic (BCtr) and from SF (BCsf), by using a 2-D histogram of the particle optical properties as a function of BC core size, as measured by the SP2. The BCtr and BCsf showed distinctly different Dc distributions and coating thicknesses, with BCsf displaying larger Dc and larger coating thickness compared to BCtr. BC particles from different sources were also apportioned by applying a multiple linear regression between the total BC mass and each AMS-PMF factor (BC–AMS–PMF method), and also attributed by applying the absorption spectral dependence of carbonaceous aerosols to 7-wavelength Aethalometer measurements (Aethalometer method). Air masses that originated from westerly (W), southeasterly (SE), and easterly (E) sectors showed BCsf fractions that ranged from low to high, and whose mass median Dc values were 137 ± 10 nm, 143 ± 11 nm and 169 ± 29 nm, respectively. The corresponding bulk relative coating thickness of BC (coated particle size/BC core – Dp/Dc) for these same sectors was 1.28 ± 0.07, 1.45 ± 0.16 and 1.65 ± 0.19. For W, SE and E air masses, the number fraction of BCsf ranged from 6 ± 2% to 11 ± 5% to 18 ± 10%, respectively, but importantly the larger BC core sizes lead to an increased fraction of BCsf in terms of mass than number (for W, SE and E air masses, the BCsf mass fractions ranged from 16 ± 6%, 24 ± 10% and 39 ± 14%, respectively). An increased fraction of non-BC particles (particles that did not contain a BC core) was also observed when SF sources were more significant. The BC mass attribution by the SP2 method agreed well with the BC–AMS–PMF multiple linear regression method (BC–AMS–PMF : SP2 ratio = 1.05, r2 = 0.80) over the entire experimental period. Good agreement was found between BCsf attributed with the Aethalometer model and the SP2. However, the assumed absorption Ångström exponent (αwb) had to be changed according to the different air mass sectors to yield the best comparison with the SP2. This could be due to influences of fuel type or burn phase.

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Exploiting multi-wavelength aerosol absorption coefficients in a multi-time resolution source apportionment study to retrieve source-dependent absorption parameters

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11235-2019 ◽

2019 ◽

Vol 19 (17) ◽

pp. 11235-11252 ◽

Cited By ~ 3

Author(s):

Alice Corina Forello ◽

Vera Bernardoni ◽

Giulia Calzolai ◽

Franco Lucarelli ◽

Dario Massabò ◽

...

Keyword(s):

Source Apportionment ◽

Biomass Burning ◽

Time Resolution ◽

Fossil Fuel ◽

Traditional Approach ◽

Optical Data ◽

Optical Parameters ◽

Bootstrap Analysis ◽

Aerosol Absorption ◽

Fossil Fuel Emissions

Abstract. In this paper, a new methodology coupling aerosol optical and chemical parameters in the same source apportionment study is reported. In addition to results on source contributions, this approach provides information such as estimates for the atmospheric absorption Ångström exponent (α) of the sources and mass absorption cross sections (MACs) for fossil fuel emissions at different wavelengths. A multi-time resolution source apportionment study using the Multilinear Engine (ME-2) was performed on a PM10 dataset with different time resolutions (24, 12, and 1 h) collected during two different seasons in Milan (Italy) in 2016. Samples were optically analysed by an in-house polar photometer to retrieve the aerosol absorption coefficient bap (in Mm−1) at four wavelengths (λ=405, 532, 635, and 780 nm) and were chemically characterized for elements, ions, levoglucosan, and carbonaceous components. The dataset joining chemically speciated and optical data was the input for the multi-time resolution receptor model; this approach was proven to strengthen the identification of sources, thus being particularly useful when important chemical markers (e.g. levoglucosan, elemental carbon) are not available. The final solution consisted of eight factors (nitrate, sulfate, resuspended dust, biomass burning, construction works, traffic, industry, aged sea salt); the implemented constraints led to a better physical description of factors and the bootstrap analysis supported the goodness of the solution. As for bap apportionment, consistent with what was expected, biomass burning and traffic were the main contributors to aerosol absorption in the atmosphere. A relevant feature of the approach proposed in this work is the possibility of retrieving a lot of other information about optical parameters; for example, in contrast to the more traditional approach used by optical source apportionment models, here we obtained source-dependent α values without any a priori assumption (α biomass burning =1.83 and α fossil fuels =0.80). In addition, the MACs estimated for fossil fuel emissions were consistent with literature values. It is worth noting that the approach presented here can also be applied using more common receptor models (e.g. EPA PMF instead of multi-time resolution ME-2) if the dataset comprises variables with the same time resolution as well as optical data retrieved by widespread instrumentation (e.g. an Aethalometer instead of in-house instrumentation).

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Source apportionment of black carbon (BC) from fossil fuel and biomass burning in metropolitan Milan, Italy

Atmospheric Environment ◽

10.1016/j.atmosenv.2019.02.009 ◽

2019 ◽

Vol 203 ◽

pp. 252-261 ◽

Cited By ~ 15

Author(s):

Amirhosein Mousavi ◽

Mohammad H. Sowlat ◽

Christopher Lovett ◽

Martin Rauber ◽

Soenke Szidat ◽

...

Keyword(s):

Black Carbon ◽

Source Apportionment ◽

Biomass Burning ◽

Fossil Fuel

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Global combustion: the connection between fossil fuel and biomass burning emissions (1997–2010)

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0177 ◽

2016 ◽

Vol 371 (1696) ◽

pp. 20150177 ◽

Cited By ~ 9

Author(s):

Jennifer K. Balch ◽

R. Chelsea Nagy ◽

Sally Archibald ◽

David M. J. S. Bowman ◽

Max A. Moritz ◽

...

Keyword(s):

Biomass Burning ◽

Urban Areas ◽

Fossil Fuel ◽

Global Scale ◽

Fossil Fuel Burning ◽

Annual Carbon ◽

Global Modelling ◽

Human Use ◽

Global Data ◽

Fossil Fuel Emissions

Humans use combustion for heating and cooking, managing lands, and, more recently, for fuelling the industrial economy. As a shift to fossil-fuel-based energy occurs, we expect that anthropogenic biomass burning in open landscapes will decline as it becomes less fundamental to energy acquisition and livelihoods. Using global data on both fossil fuel and biomass burning emissions, we tested this relationship over a 14 year period (1997–2010). The global average annual carbon emissions from biomass burning during this time were 2.2 Pg C per year (±0.3 s.d.), approximately one-third of fossil fuel emissions over the same period (7.3 Pg C, ±0.8 s.d.). There was a significant inverse relationship between average annual fossil fuel and biomass burning emissions. Fossil fuel emissions explained 8% of the variation in biomass burning emissions at a global scale, but this varied substantially by land cover. For example, fossil fuel burning explained 31% of the variation in biomass burning in woody savannas, but was a non-significant predictor for evergreen needleleaf forests. In the land covers most dominated by human use, croplands and urban areas, fossil fuel emissions were more than 30- and 500-fold greater than biomass burning emissions. This relationship suggests that combustion practices may be shifting from open landscape burning to contained combustion for industrial purposes, and highlights the need to take into account how humans appropriate combustion in global modelling of contemporary fire. Industrialized combustion is not only an important driver of atmospheric change, but also an important driver of landscape change through companion declines in human-started fires. This article is part of the themed issue ‘The interaction of fire and mankind’.

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Sources and transport of Δ<sup>14</sup>C on CO<sub>2</sub> within the Mexico City Basin and vicinity

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-7213-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 7213-7237 ◽

Cited By ~ 2

Author(s):

S. A. Vay ◽

S. C. Tyler ◽

Y. Choi ◽

D. R. Blake ◽

N. J. Blake ◽

...

Keyword(s):

Mexico City ◽

Biomass Burning ◽

North American ◽

Nuclear Power ◽

Fossil Fuel ◽

Co2 Flux ◽

Waste Incineration ◽

Background Value ◽

The North ◽

Fossil Fuel Emissions

Abstract. Radiocarbon samples taken over Mexico City and the surrounding region during the MILAGRO field campaign in March 2006 exhibited an unexpected distribution: (1) relatively few samples (23%) were below the North American free tropospheric background value (57‰) despite the fossil fuel emissions from one of the world's most highly polluted environments; and (2) frequent enrichment well above the background value was observed. Correlate source tracer species and air transport characteristics were examined to elucidate influences on the radiocarbon distribution. Our analysis suggests that a combination of radiocarbon sources biased the "regional radiocarbon background" above the North American value thereby decreasing the apparent fossil fuel signature. These sources included the release of bomb or "hot" radiocarbon sequestered in plant carbon pools via the ubiquitous biomass burning in the region as well as the direct release of radiocarbon as CO2. Plausible large local perturbations include the burning of hazardous waste in cement kilns; medical waste incineration; and emissions from the Laguna Verde Nuclear Power Plant. These observations provide insight into the use of Δ14CO2 to constrain fossil fuel emissions in the megacity environment, indicating that underestimation of the fossil fuel contribution to the CO2 flux is likely wherever biomass burning coexists with urban emissions. Our findings increase the complexity required to quantify fossil fuel-derived CO2 in source-rich environments characteristic of megacities, and have implications for the use of Δ14CO2 observations in evaluating bottoms-up emission inventories and their reliability as a tool for validating national emission claims of CO2 within the framework of the Kyoto Protocol.

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