scholarly journals Mass absorption cross-section of flare-generated black carbon: Variability, predictive model, and implications

Carbon ◽  
2019 ◽  
Vol 149 ◽  
pp. 760-771 ◽  
Author(s):  
B.M. Conrad ◽  
M.R. Johnson
Keyword(s):  
Predictive Model ◽  
Black Carbon ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Mass Absorption

scholarly journals Variability in the mass absorption cross-section of black carbon (BC) aerosols is driven by BC internal mixing state at a central European background site (Melpitz, Germany) in winter

2020 ◽  
Author(s):  
Jinfeng Yuan ◽  
Robin Lewis Modini ◽  
Marco Zanatta ◽  
Andreas B. Herber ◽  
Thomas Müller ◽  
...  
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
Cross Section ◽  
Coating Thickness ◽  
Absorption Cross Section ◽  
Correlation Method ◽  
Absorption Cross ◽  
Core Size ◽  
Background Site ◽  
Mass Absorption

Abstract. Properties of atmospheric black carbon (BC) particles were characterized during a field experiment at a rural background site (Melpitz, Germany) in February 2017. BC absorption at a wavelength of 870 nm was measured by a photoacoustic extinctiometer and BC physical properties (BC mass concentration, core size distribution and coating thickness) were measured by a single-particle soot photometer (SP2). Additionally, a catalytic stripper was used to intermittently remove BC coatings by alternating between ambient and thermo-denuded conditions. From these data the mass absorption cross section of BC (MACBC) and its enhancement factor (EMAC) were inferred. Two methods were applied independently to investigate the coating effect on EMAC: a correlation method (ambient MACBC vs. BC coating thickness) and a denuding method (MACBC,amb vs. MACBC,denuded). Observed EMAC values varied from 1.0 to 1.6 (lower limit from denuding method) or ~ 1.2 to 1.9 (higher limit from correlation method) with the mean coating volume fraction ranging from 54 to 78 % in the dominating mass equivalent BC core diameter range of 200–220 nm. MACBC and EMAC were strongly correlated with coating thickness of BC, while other factors were found to have a potential minor influence as well, including air mass origins (different BC sources), mixing morphology (ratio of inorganics to organics), BC core size distribution and absorption Ångström exponent (AAE). These results for ambient BC measured at Melpitz during winter show that the lensing effect caused by coatings on BC is the main driver of the variations in MACBC and EMAC, while changes in other BC particle properties such as source, BC core size or coating composition play only minor roles.

Mass Absorption Cross-Section of Ambient Black Carbon Aerosol in Relation to Chemical Age

2009 ◽  
Vol 43 (6) ◽  
pp. 522-532 ◽  
Author(s):  
A. Knox ◽  
G. J. Evans ◽  
J. R. Brook ◽  
X. Yao ◽  
C.-H. Jeong ◽  
...  
Keyword(s):  
Black Carbon ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Mass Absorption ◽  
Black Carbon Aerosol

scholarly journals Black carbon physical and optical properties across northern India during pre-monsoon and monsoon seasons

2019 ◽  
Vol 19 (20) ◽  
pp. 13079-13096 ◽  
Author(s):  
James Brooks ◽  
Dantong Liu ◽  
James D. Allan ◽  
Paul I. Williams ◽  
Jim Haywood ◽  
...  
Keyword(s):  
Black Carbon ◽  
Cross Section ◽  
Coating Thickness ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
North West ◽  
North East India ◽  
Mass Absorption ◽  
North East ◽  
The North

Abstract. Black carbon (BC) is known to have major impacts on both climate and human health and is therefore of global importance, particularly in regions close to large populations that have strong sources. The size-resolved mixing state of BC-containing particles was characterised using a single-particle soot photometer (SP2). The study focusses on the Indo-Gangetic Plain (IGP) during the pre-monsoon and monsoon seasons. Data presented are from the UK Facility for Airborne Atmospheric Measurements BAe-146 research aircraft that performed flights during the pre-monsoon (11 and 12 June) and monsoon (30 June to 11 July) seasons of 2016. Over the IGP, BC mass concentrations were greater (1.95 µg m−3) compared to north-west India (1.50 µg m−3) and north-east India (0.70 µg m−3) during the pre-monsoon season. Across northern India, two distinct BC modes were recorded; a mode of small BC particles (core diameter <0.16 µm and coating thickness <50 nm) and a mode of moderately coated BC (core diameter <0.22 µm and coating thickness of 50–200 nm). The IGP and north-east India locations exhibited moderately coated black carbon particles with enhanced coating thicknesses, core sizes, mass absorption cross sections, and scattering enhancement values compared to much lower values present in the north-west. The coating thickness and mass absorption cross section increased with altitude (13 %) compared to those in the boundary layer. As the monsoon arrived across the region, mass concentration of BC decreased over the central IGP and north-east locations (38 % and 28 % respectively), whereas for the north-west location BC properties remained relatively consistent. Post-monsoon onset, the coating thickness, core size, mass absorption cross section, and scattering enhancement values were all greatest over the central IGP much like the pre-monsoon season but were considerably reduced over both north-east and north-west India. Increases in mass absorption cross section through the atmospheric column were still present during the monsoon for the north-west and central IGP locations, but less so over the north-east due to lack of long-range transport aerosol aloft. Across the Indo-Gangetic Plain and north-east India during the pre-monsoon and monsoon seasons, solid-fuel (wood burning) emissions form the greatest proportion of BC with moderately coated particles. However, as the monsoon develops in the north-east there was a switch to small uncoated BC particles indicative of traffic emissions, but the solid-fuel emissions remained in the IGP into the monsoon. For both seasons in the north-west, traffic emissions form the greatest proportion of BC particles. Our findings will prove important for greater understanding of the BC physical and optical properties, with important consequences for the atmospheric radiative forcing of BC-containing particles. The findings will also help constrain the regional aerosol models for a variety of applications such as space-based remote sensing, chemistry transport modelling, air quality, and BC source and emission inventories.

scholarly journals An Exploratory Approach Using Regression and Machine Learning in the Analysis of Mass Absorption Cross Section of Black Carbon Aerosols: Model Development and Evaluation

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1185
Author(s):  
Hanyang Li ◽  
Andrew A. May
Keyword(s):  
Support Vector Machine ◽  
Black Carbon ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Radiative Forcing ◽  
Support Vector ◽  
Absorption Cross ◽  
Mass Absorption ◽  
Theoretical Approaches ◽  
Analytical Approaches

Mass absorption cross-section of black carbon (MACBC) describes the absorptive cross-section per unit mass of black carbon, and is, thus, an essential parameter to estimate the radiative forcing of black carbon. Many studies have sought to estimate MACBC from a theoretical perspective, but these studies require the knowledge of a set of aerosol properties, which are difficult and/or labor-intensive to measure. We therefore investigate the ability of seven data analytical approaches (including different multivariate regressions, support vector machine, and neural networks) in predicting MACBC for both ambient and biomass burning measurements. Our model utilizes multi-wavelength light absorption and scattering as well as the aerosol size distributions as input variables to predict MACBC across different wavelengths. We assessed the applicability of the proposed approaches in estimating MACBC using different statistical metrics (such as coefficient of determination (R2), mean square error (MSE), fractional error, and fractional bias). Overall, the approaches used in this study can estimate MACBC appropriately, but the prediction performance varies across approaches and atmospheric environments. Based on an uncertainty evaluation of our models and the empirical and theoretical approaches to predict MACBC, we preliminarily put forth support vector machine (SVM) as a recommended data analytical technique for use. We provide an operational tool built with the approaches presented in this paper to facilitate this procedure for future users.

scholarly journals Estimation of the mass absorption cross section of the organic carbon component of aerosols in the Mexico City Metropolitan Area (MCMA)

2008 ◽  
Vol 8 (3) ◽  
pp. 10189-10225 ◽  
Author(s):  
J. C. Barnard ◽  
R. Volkamer ◽  
E. I. Kassianov
Keyword(s):  
Organic Carbon ◽  
Black Carbon ◽  
Mexico City ◽  
Cross Section ◽  
Light Absorption ◽  
Absorption Cross Section ◽  
Trace Gases ◽  
Absorption Cross ◽  
Enhanced Absorption ◽  
Mass Absorption

Abstract. Data taken from the MCMA-2003 and the 2006 MILAGRO field campaigns are used to examine the absorption of solar radiation by the organic component of aerosols. Using irradiance data from a Multi-Filter Rotating Shadowband Radiometer (MFRSR) and an actinic flux spectroradiometer (SR), we derive aerosol single scattering albedo, π0,λ, as a function of wavelength, λ. We find that in the near-UV spectral range (250 to 400 nm) π0,λ is much lower compared to π0,λ at 500 nm indicating enhanced absorption in the near-UV range. Absorption by elemental carbon, dust, or gas cannot account for this enhanced absorption leaving the organic part of the aerosol as the only possible absorber. We use data from a surface deployed Aerodyne Aerosol Mass Spectrometer (AMS) along with the inferred π0,λ to estimate the Mass Absorption Cross section (MAC) for the organic carbon. We find that the MAC is about 10.5 m2/g at 300 nm and falls close to zero at about 500 nm; values that are roughly consistent with other estimates of organic carbon MAC. These MAC values can be considered as "radiatively correct" because when used in radiative transfer calculations the calculated irradiances/actinic fluxes match those measured at the wavelengths considered here. For an illustrative case study described here, we estimate that the light absorption by the "brown" (organic) carbonaceous aerosol can add about 40% to the light absorption of black carbon in Mexico City. This contribution will vary depending on the relative abundance of organic carbon relative to black carbon. Furthermore, our analysis indicates that organic aerosol would slow down photochemistry by selectively scavenging the light reaching the ground at those wavelengths that drive photochemical reactions. Finally, satellite retrievals of trace gases that are used to infer emissions currently assume that the MAC of organic carbon is zero. For trace gases that are retrieved using wavelengths shorter then 420 nm (i.e. SO2, HCHO, halogenoxides, NO2), the assumption of non-zero MAC values will induce an upward correction to the inferred emissions. This will be particularly relevant in polluted urban atmospheres and areas of biomass burning where organic aerosols are particularly abundant.

Sign in / Sign up

Export Citation Format

Share Document