scholarly journals Unexpected Biomass Burning Aerosol Absorption Enhancement Explained by Black Carbon Mixing State

2020 ◽  
Vol 47 (19) ◽  
Author(s):  
Cyrielle Denjean ◽  
Joel Brito ◽  
Quentin Libois ◽  
Marc Mallet ◽  
Thierry Bourrianne ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Aerosol Absorption ◽  
Biomass Burning Aerosol

scholarly journals Absorption closure in highly aged biomass burning smoke

2020 ◽  
Vol 20 (19) ◽  
pp. 11201-11221 ◽  
Author(s):  
Jonathan W. Taylor ◽  
Huihui Wu ◽  
Kate Szpek ◽  
Keith Bower ◽  
Ian Crawford ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Climate Models ◽  
Global Climate ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Airborne Measurements ◽  
Aerosol Absorption ◽  
Visible Wavelengths ◽  
The Impact

Abstract. The optical properties of black carbon (BC) are a major source of uncertainty in regional and global climate studies. In the past, detailed investigation of BC absorption has been hampered by systematic biases in the measurement instrumentation. We present airborne measurements of aerosol absorption and black carbon microphysical properties in highly aged biomass burning plumes measured 4–8 d from their source over the southeast Atlantic Ocean during CLARIFY-2017, using a suite of novel photoacoustic spectrometers to measure aerosol absorption at 405, 514, and 655 nm and a single-particle soot photometer to measure the BC mass concentration, size, and mixing state. These measurements are of sufficient quality and detail to provide constraint on optical schemes used in climate models for the first time in biomass burning plumes far from their source – an aerosol environment that is one of the most important climatically. The average absorption Ångström exponents (AAE) were 1.38 over the wavelength range from 405 to 514 nm and 0.88 over the range from 514 to 655 nm, suggesting that brown carbon (BrC) contributed to 11±2 % of absorption at 405 nm. The effective organic aerosol (OA) mass absorption coefficient (MAC) was 0.31±0.09 m2 g−1 at 405 nm. The BC particles were universally thickly coated, and almost no externally mixed BC particles were detected. The average MAC of BC was 20±4, 15±3, and 12±2 m2g−1 at wavelengths of 405, 514, and 655 nm respectively, with equivalent absorption enhancements of around 1.85±0.45 at all three wavelengths, suggesting that the thick coatings acted as a lens that enhanced light absorption by the BC. We compared the measured MAC and AAE values with those calculated using several optical models and absorption parameterisations that took the measured BC mass and mixing state as inputs. Homogeneous grey-sphere Mie models were only able to replicate MAC for some low (real and imaginary) values of the complex BC refractive index (mBC) at the shortest wavelength, but they would have to use unrealistically low values of mBC to accurately replicate the AAE. A core–shell Mie model was able to generate good agreement for MAC in the green–red end of the visible spectrum for most values of mBC. However, there are no possible values of mBC that produce MAC values that agree with our observations at all three wavelengths, due to a wavelength-dependent underestimation of the MAC of the underlying BC core. Four semiempirical parameterisations from the literature were also tested, linking the BC mixing state to either the MAC or absorption enhancement. Two of these schemes produced results that agreed within a few percent with the measured MAC at all three wavelengths, and the AAE agreed well when discounting the effects of BrC. Our results uniquely demonstrate the validity of absorption parameterisations, as well as the failings of Mie calculations, in this highly aged environment. We recommend that future work should conduct similar analyses in environments where BC has different properties; future studies should also investigate the impact of implementing these types of schemes within climate models as well as the impact of developing equivalent schemes for light scattering by soot particles at visible wavelengths.

scholarly journals Absorption closure in highly aged biomass burning smoke

2020 ◽  
Author(s):  
Jonathan W. Taylor ◽  
Huihui Wu ◽  
Kate Szpek ◽  
Keith Bower ◽  
Ian Crawford ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Climate Models ◽  
Global Climate ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Airborne Measurements ◽  
Aerosol Absorption ◽  
Visible Wavelengths ◽  
The Impact

Abstract. The optical properties of black carbon (BC) are a major source of uncertainty in regional and global climate studies. In the past, detailed investigation of BC absorption has been hampered by systematic biases in the measurement instrumentation. We present airborne measurements of aerosol absorption and black carbon microphysical properties in highly aged biomass burning plumes measured over the southeast Atlantic ocean during CLARIFY-2017, using a suite of novel photoacoustic spectrometers to measure 5 aerosol absorption at 405 nm, 514 nm, and 655 nm, and a single-particle soot photometer to measure the BC mass concentration, size, and mixing state. These measurements are of sufficient quality and detail to provide constraint on optical schemes used in climate models for the first time in biomass burning plumes far from source, an aerosol environment that is one of the most important climatically. The average absorption Angstrom exponents (AAE) were 1.39 over the wavelength range 405–514 nm, and 0.94 over the range 514–655 nm, suggesting brown carbon (BrC) contributed to 10 ± 2 % of absorption at 405 nm. The effective OA mass absorption coefficient (MAC) was 0.27 ± 0.08 m2 g−1 at 405 nm. The BC particles were universally thickly-coated, and almost no externally-mixed BC particles were detected. The MAC of BC was also high, with equivalent absorption enhancements of around 1.8 at all three wavelengths, suggesting that the thick coatings acted as a lens that enhanced light absorption by the BC. We compared the measured MAC and AAE values with those calculated using several optical models and absorption parametrisations that took the measured BC mass and mixing state as inputs. Homogeneous grey sphere Mie models were only able to replicate MAC for some low (real and imaginary) values of the complex BC refractive index (mBC) at the shortest wavelength, but they would have to use unrealistically low values of mBC to accurately replicate AAE. A core/shell Mie model was able to generate good agreement for MAC in the green/red end of the visible spectrum for most values of mBC. However, there are no possible values of mBC that produce MAC values that agree with our observations at all three wavelengths, due to a wavelength-dependent underestimation of the MAC of the underlying BC core. Four semi-empirical parametrisations from literature were also tested, linking BC mixing state to either MAC or absorption enhancement. Two of these schemes produced results that agreed within a few percent of the measured MAC at all three wavelengths, and AAE agreed well when discounting the effects of BrC. Our results uniquely demonstrate the validity of absorption parametrisations, as well as the failings of Mie calculations, in this highly aged environment. We recommend future work should conduct similar analyses in environments where BC has different properties, and investigate the impact of implementing these types of schemes within climate models, as well as developing equivalent schemes for light scattering by soot particles at visible wavelengths.

scholarly journals Strong Light Absorption Induced by Aged Biomass Burning Black Carbon over the Southeastern Tibetan Plateau in Pre-monsoon Season

2020 ◽  
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by 13 times, and greatly elevated the number fraction of thickly-coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell/core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation of the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction and higher aging degree of BC particles in the upper atmosphere. Resulted from both increase of BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by 15 times, in which 21 % was contributed by the BC aging and 79 % was contributed from the increase of BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

scholarly journals Measurement report: Strong light absorption induced by aged biomass burning black carbon over the southeastern Tibetan Plateau in pre-monsoon season

2021 ◽  
Vol 21 (11) ◽  
pp. 8499-8510
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by a factor of 13 and greatly elevated the number fraction of thickly coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell / core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation in the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction, and higher aging degree of BC particles in the upper atmosphere. Resulting from both increase in BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by a factor of 15, of which 21 % was contributed by the BC aging, and 79 % was contributed from the increase in BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

Mixing state and light absorption enhancement of black carbon aerosols in summertime Nanjing, China

2020 ◽  
Vol 222 ◽  
pp. 117141 ◽  
Author(s):  
Yan Ma ◽  
Congcong Huang ◽  
Halim Jabbour ◽  
Zewen Zheng ◽  
Yibo Wang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

scholarly journals Mixing characteristics of refractory black carbon aerosols determined by a tandem CPMA-SP2 system at an urban site in Beijing

2019 ◽  
Author(s):  
Hang Liu ◽  
Xiaole Pan ◽  
Dantong Liu ◽  
Xiaoyong Liu ◽  
Xueshun Chen ◽  
...  
Keyword(s):  
Black Carbon ◽  
Fractal Structure ◽  
Particle Mass ◽  
Shell Structures ◽  
Absorption Enhancement ◽  
Urban Site ◽  
Core Shell ◽  
Mixing State ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. Black carbon aerosols play an important role in climate change by absorbing solar radiation and degrading visibility. In this study, the mixing state of refractory black carbon (rBC) at an urban site in Beijing was studied with a single particle soot photometer (SP2), as well as a tandem observation system with a centrifugal particle mass analyzer (CPMA) and a differential mobility analyzer (DMA), in early summer of 2018. The results demonstrated that the mass-equivalent size distribution of rBC exhibited an approximately lognormal distribution with a mass median diameter (MMD) of 171.2 nm. When the site experienced prevailing southerly winds, the MMD of rBC increased notably by 19 %. During the observational period, the ratio of the diameter of rBC-containing particles (Dp) to the rBC core (Dc) was 1.20 on average for Dc = 180 nm, indicating that the majority of rBC particles were thinly coated. The Dp / Dc value exhibited a clear diurnal pattern, with a maximum at 1400 LST and an enhancing rate of 0.013/h; higher Ox conditions increased the coating enhancing rate. Bare rBC particles were primarily in a fractal structure with a mass fractal dimension (Dfm) of 2.35, with limited variation during both clean and pollution periods, indicating significant impacts from on-road vehicle emissions. The morphology of rBC-containing particles vairied with aging processes. The mixing state of rBC particles could be indicated by the mass ratio of non-refractory matter to rBC (MR). In the present study, rBC-containing particles were primarily found in an external fractal structure when MR  6, at which the measured scattering cross section of rBC-containing particles was consistent with that based on the Mie-scattering simulation. We found only 9 % of the rBC-containing particles were in core-shell structures on clean days with a particle mass of 10 fg, and the number fraction of core-shell structures increased considerably to 32 % on pollution days. Considering the morphology change, the absorption enhancement (Eabs) was 11.7 % higher based on core-shell structures. This study highlights the combined effects of morphology and coating thickness on the Eabs of rBC-containing particles, which will be helpful for determining the climatic effects of BC.

scholarly journals Parameterization of single-scattering albedo (SSA) and absorption Ångström exponent (AAE) with EC / OC for aerosol emissions from biomass burning

2016 ◽  
Vol 16 (15) ◽  
pp. 9549-9561 ◽  
Author(s):  
Rudra P. Pokhrel ◽  
Nick L. Wagner ◽  
Justin M. Langridge ◽  
Daniel A. Lack ◽  
Thilina Jayarathne ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Single Scattering ◽  
Emission Factors ◽  
Single Scattering Albedo ◽  
Biomass Fuels ◽  
Brown Carbon ◽  
Pearson's R ◽  
Biomass Burning Aerosol ◽  
Pearson’S R

Abstract. Single-scattering albedo (SSA) and absorption Ångström exponent (AAE) are two critical parameters in determining the impact of absorbing aerosol on the Earth's radiative balance. Aerosol emitted by biomass burning represent a significant fraction of absorbing aerosol globally, but it remains difficult to accurately predict SSA and AAE for biomass burning aerosol. Black carbon (BC), brown carbon (BrC), and non-absorbing coatings all make substantial contributions to the absorption coefficient of biomass burning aerosol. SSA and AAE cannot be directly predicted based on fuel type because they depend strongly on burn conditions. It has been suggested that SSA can be effectively parameterized via the modified combustion efficiency (MCE) of a biomass burning event and that this would be useful because emission factors for CO and CO2, from which MCE can be calculated, are available for a large number of fuels. Here we demonstrate, with data from the FLAME-4 experiment, that for a wide variety of globally relevant biomass fuels, over a range of combustion conditions, parameterizations of SSA and AAE based on the elemental carbon (EC) to organic carbon (OC) mass ratio are quantitatively superior to parameterizations based on MCE. We show that the EC ∕ OC ratio and the ratio of EC ∕ (EC + OC) both have significantly better correlations with SSA than MCE. Furthermore, the relationship of EC ∕ (EC + OC) with SSA is linear. These improved parameterizations are significant because, similar to MCE, emission factors for EC (or black carbon) and OC are available for a wide range of biomass fuels. Fitting SSA with MCE yields correlation coefficients (Pearson's r) of  ∼  0.65 at the visible wavelengths of 405, 532, and 660 nm while fitting SSA with EC / OC or EC / (EC + OC) yields a Pearson's r of 0.94–0.97 at these same wavelengths. The strong correlation coefficient at 405 nm (r =  0.97) suggests that parameterizations based on EC / OC or EC / (EC + OC) have good predictive capabilities even for fuels in which brown carbon absorption is significant. Notably, these parameterizations are effective for emissions from Indonesian peat, which have very little black carbon but significant brown carbon (SSA  =  0.990 ± 0.001 at 532 and 660 nm, SSA  =  0.937 ± 0.011 at 405 nm). Finally, we demonstrate that our parameterization based on EC / (EC + OC) accurately predicts SSA during the first few hours of plume aging with data from Yokelson et al. (2009) gathered during a biomass burning event in the Yucatán Peninsula of Mexico.

scholarly journals Emission characteristics of refractory black carbon aerosols from fresh biomass burning: a perspective from laboratory experiments

2017 ◽  
Vol 17 (21) ◽  
pp. 13001-13016 ◽  
Author(s):  
Xiaole Pan ◽  
Yugo Kanaya ◽  
Fumikazu Taketani ◽  
Takuma Miyakawa ◽  
Satoshi Inomata ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Combustion Efficiency ◽  
High Temporal Resolution ◽  
Equivalent Diameter ◽  
Emission Characteristics ◽  
Mixing State ◽  
Climate Effect ◽  
Essential Information ◽  
Background Values

Abstract. The emission characteristics of refractory black carbon (rBC) from biomass burning are essential information for numerical simulations of regional pollution and climate effects. We conducted combustion experiments in the laboratory to investigate the emission ratio and mixing state of rBC from the burning of wheat straw and rapeseed plants, which are the main crops cultivated in the Yangtze River Delta region of China. A single particle soot photometer (SP2) was used to measure rBC-containing particles at high temporal resolution and with high accuracy. The combustion state of each burning case was indicated by the modified combustion efficiency (MCE), which is calculated using the integrated enhancement of carbon dioxide and carbon monoxide concentrations relative to their background values. The mass size distribution of the rBC particles showed a lognormal shape with a mode mass equivalent diameter (MED) of 189 nm (ranging from 152 to 215 nm), assuming an rBC density of 1.8 g cm−3. rBC particles less than 80 nm in size (the lower detection limit of the SP2) accounted for ∼ 5 % of the total rBC mass, on average. The emission ratios, which are expressed as ΔrBC ∕ ΔCO (Δ indicates the difference between the observed and background values), displayed a significant positive correlation with the MCE values and varied between 1.8 and 34 ng m−3 ppbv−1. Multi-peak fitting analysis of the delay time (Δt, or the time of occurrence of the scattering peak minus that of the incandescence peak) distribution showed that rBC-containing particles with rBC MED  =  200 ± 10 nm displayed two peaks at Δt  =  1.7 µs and Δt  =  3.2 µs, which could be attributed to the contributions from both flaming and smoldering combustion in each burning case. Both the Δt values and the shell / core ratios of the rBC-containing particles clearly increased as the MCE decreased from 0.98 (smoldering-dominant combustion) to 0.86 (flaming-dominant combustion), implying the great importance of the rapid condensation of semi-volatile organics. This laboratory study found that the mixing state of rBC particles from biomass burning strongly depends on its combustion processes, and overall MCE should be taken carefully into consideration while the climate effect of rBC particles from open biomass burning is simulated.

scholarly journals Impact of mixing state and hygroscopicity on CCN activity of biomass burning aerosol in Amazonia

2016 ◽  
Author(s):  
Madeleine Sánchez Gácita ◽  
Karla M. Longo ◽  
Julliana L. M. Freire ◽  
Saulo R. Freitas ◽  
Scot T. Martin
Keyword(s):  
Biomass Burning ◽  
General Circulation ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
General Circulation Models ◽  
Mixing State ◽  
Activation Kinetics ◽  
Cloud Properties ◽  
Aerosol Mass ◽  
Biomass Burning Aerosol

Abstract. Smoke aerosols prevail throughout Amazonia because of widespread biomass burning during the dry season. External mixing, low variability in the particle size distribution and low particle hygroscopicity are typical. There can be profound effects on cloud properties. This study uses an adiabatic cloud model to simulate the activation of smoke particles as cloud condensation nuclei (CCN) and to assess the relative importance of variability in hygroscopicity, mixing state, and activation kinetics for the activated fraction and maximum supersaturation. The analysis shows that use of medium values of hygroscopicity representative of smoke aerosols for other biomass burning regions on Earth can lead to significant errors, compared to the use of low hygroscopicity reported for Amazonia. Kinetic limitations, which can be significant for medium and high hygroscopicity, did not play a strong role for CCN activation of particles representative of Amazonia smoke aerosols, even when taking into account the large aerosol mass and number concentrations typical of the region. Internal compared to external mixing of particle components of variable hygroscopicity resulted in a significant overestimation of the activated fraction. These findings on uncertainties and sensitivities provide guidance on appropriate simplifications that can be used for modeling of smoke aerosols within general circulation models.

scholarly journals Aerosol light absorption and the role of extremely low volatility organic compounds

2020 ◽  
Vol 20 (19) ◽  
pp. 11625-11637
Author(s):  
Antonios Tasoglou ◽  
Evangelos Louvaris ◽  
Kalliopi Florou ◽  
Aikaterini Liangou ◽  
Eleni Karnezi ◽  
...  
Keyword(s):  
Black Carbon ◽  
Organic Compounds ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Scanning Mobility Particle Sizer ◽  
Brown Carbon ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Particle Sizer

Abstract. A month-long set of summertime measurements in a remote area in the Mediterranean is used to quantify aerosol absorption and the role of black and brown carbon. The suite of instruments included a high-resolution aerosol mass spectrometer (HR-ToF-AMS) and a scanning mobility particle sizer (SMPS), both coupled to a thermodenuder and an Aethalometer, a photoacoustic extinctiometer (PAX405), and a single particle soot photometer (SP2). The average refractory black carbon (rBC) concentration during the campaign was 0.14 µg m−3, representing 3 % of the fine aerosol mass. The measured light absorption was two or more times higher than that of fresh black carbon (BC). Mie theory indicated that the absorption enhancement due to the coating of BC cores by nonrefractory material could explain only part of this absorption enhancement. The role of brown carbon (BrC) and other non-BC light-absorbing material was then investigated. A good correlation (R2=0.76) between the unexplained absorption and the concentration of extremely low volatility organic compounds (ELVOCs) mass was found.

Sign in / Sign up

Export Citation Format

Share Document