An Investigation on Morphology and Fractal Dimension of Diesel and Diesel‑Biodiesel Soot Agglomerates

Guarieiro, Aline Lefol Nani; Eiguren-Fernandez, Arantzazu; Rocha, Gisele O. da; Andrade, Jailson B. de

doi:10.21577/0103-5053.20160306

Cited by 3 publications

(3 citation statements)

References 46 publications

(99 reference statements)

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“…The SSA also increases with D mob and D f ; the latter is explained by the decreasing scattering in loosely packed BCFAs. This is due to compact aggregates following a Rayleigh-like polarization curve (Gustafson and Kolokolova, 1999). The asymmetry parameter (g) (panel d) shows a range of values between 0 and 1 for D mob values between 24 and 810 nm.…”

Section: Dependency Of Bcfa Optical Properties On the Morphologymentioning

confidence: 93%

Optical properties of coated black carbon aggregates: numerical simulations, radiative forcing estimates, and size-resolved parameterization scheme

et al. 2021

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Abstract. The formation of black carbon fractal aggregates (BCFAs) from combustion and subsequent ageing involves several stages resulting in modifications of particle size, morphology, and composition over time. To understand and quantify how each of these modifications influences the BC radiative forcing, the optical properties of BCFAs are modelled. Owing to the high computational time involved in numerical modelling, there are some gaps in terms of data coverage and knowledge regarding how optical properties of coated BCFAs vary over the range of different factors (size, shape, and composition). This investigation bridged those gaps by following a state-of-the-art description scheme of BCFAs based on morphology, composition, and wavelength. The BCFA optical properties were investigated as a function of the radius of the primary particle (ao), fractal dimension (Df), fraction of organics (forganics), wavelength (λ), and mobility diameter (Dmob). The optical properties are calculated using the multiple-sphere T-matrix (MSTM) method. For the first time, the modelled optical properties of BC are expressed in terms of mobility diameter (Dmob), making the results more relevant and relatable for ambient and laboratory BC studies. Amongst size, morphology, and composition, all the optical properties showed the highest variability with changing size. The cross sections varied from 0.0001 to 0.1 µm2 for BCFA Dmob ranging from 24 to 810 nm. It has been shown that MACBC and single-scattering albedo (SSA) are sensitive to morphology, especially for larger particles with Dmob > 100 nm. Therefore, while using the simplified core–shell representation of BC in global models, the influence of morphology on radiative forcing estimations might not be adequately considered. The Ångström absorption exponent (AAE) varied from 1.06 up to 3.6 and increased with the fraction of organics (forganics). Measurement results of AAE ≫ 1 are often misinterpreted as biomass burning aerosol, it was observed that the AAE of purely black carbon particles can be ≫ 1 in the case of larger BC particles. The values of the absorption enhancement factor (Eλ) via coating were found to be between 1.01 and 3.28 in the visible spectrum. The Eλ was derived from Mie calculations for coated volume equivalent spheres and from MSTM for coated BCFAs. Mie-calculated enhancement factors were found to be larger by a factor of 1.1 to 1.5 than their corresponding values calculated from the MSTM method. It is shown that radiative forcings are highly sensitive to modifications in morphology and composition. The black carbon radiative forcing ΔFTOA (W m−2) decreases up to 61 % as the BCFA becomes more compact, indicating that global model calculations should account for changes in morphology. A decrease of more than 50 % in ΔFTOA was observed as the organic content of the particle increased up to 90 %. The changes in the ageing factors (composition and morphology) in tandem result in an overall decrease in the ΔFTOA. A parameterization scheme for optical properties of BC fractal aggregates was developed, which is applicable for modelling, ambient, and laboratory-based BC studies. The parameterization scheme for the cross sections (extinction, absorption, and scattering), single-scattering albedo (SSA), and asymmetry parameter (g) of pure and coated BCFAs as a function of Dmob were derived from tabulated results of the MSTM method. Spanning an extensive parameter space, the developed parameterization scheme showed promisingly high accuracy up to 98 % for the cross sections, 97 % for single-scattering albedos (SSAs), and 82 % for the asymmetry parameter (g).

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Section: Dependency Of Bcfa Optical Properties On the Morphologymentioning

confidence: 93%

Optical properties of coated black carbon aggregates: numerical simulations, radiative forcing estimates, and size-resolved parameterization scheme

et al. 2021

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“…As biodiesel has increasing its popularity together with the perceptive reductions of fossil fuel reserves worldwide, it has been used to partially replace fossil diesel as fuel, used mostly in unmodified diesel engines. [12][13][14][15][16][17][18][19] In regard to regulated emissions, the diesel/ biodiesel blends bring some environmental advantages, such as the reduction in the emissions of PM, carbon monoxide (CO), carbon dioxide (CO 2 ), sulfur oxides (SO x ) and hydrocarbons (HC), even though there is an increase in nitrogen oxides (NOx) emissions. 5 But when taking into account unregulated pollutants (such as carbonyls and polycyclic aromatic compounds (PAHs), among others), it was found biodiesel may increase emission levels of some of these substances, [13][14][15][16]18,19 although contradictory results are reported, [20][21][22] probably due to the differences in the engine technology, fuel composition, and driving regime.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is still uncertain if biodiesel-exhausted particles (BEP) would be more or less toxic than DEP. Despite the fact some studies have tried to address this issue, 4,16,17,23,24 the toxicity of traffic-related urban PM is still not completely understood and more studies are needed.…”

Section: Introductionmentioning

confidence: 99%

In vitro Evaluation of Oxidative Stress Caused by Fine Particles (PM2.5) Exhausted from Heavy-Duty Vehicles Using Diesel/Biodiesel Blends under Real World Conditions

Jesus¹,

Mosca²,

Guarieiro³

et al. 2017

J. Braz. Chem. Soc.

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In this work, the redox activity of fine diesel/biodiesel particulate matter (PM 2.5 ) was studied in order to approach its toxicity from reactive oxygen species, due to adverse effects it may cause to human health. The oxidative potential was measured by the dithiothreitol (DTT) assay in order to study the relative contribution of water-soluble transition metals, polycyclic aromatic compounds (PAH), nitro-PAH, and quinones. It was analyzed a total of 24 samples collected from primarily diesel/biodiesel-exhausted particles from buses. The rate concentrations of PM 2.5 redox activity ranged 0.020-0.069 nmol min -1 μg -1, with median at 0.040 nmol min -1 μg -1 (on average, 0.042 ± 0.005 nmol min -1 μg -1 for morning, 0.033 ± 0.007 nmol min -1 μg -1 for afternoon and 0.045 ± 0.009 nmol min -1 μg -1 for night). The transition metals appear to dominate the DTT response, since they were responsible up to 89% of redox activity measured in the samples. Apparently, the metal fraction contained in PM 2.5 demonstrated a greater ability to catalyze reactions that promote the formation of reactive oxygen species when compared to organic compounds. It was observed that the oxidative potential of PM 2.5 particles emitted from diesel/biodiesel (B7) is similar to diesel-emitted particles.

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Characteristics and Aging of Traffic-Emitted Particles with Sulfate and Organic Compound Formation in Urban Air

et al. 2022

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Traffic is a major source of anthropogenic aerosol in urban atmosphere. In this study, aerosol particles were measured with a TEM-EDX system at the roadside of a main road in the northwestern part of Beijing, China, under clear and hazy conditions. Soot, organic, sulfur-rich (S-rich), mineral, and metal particles, as well as the mixtures, were frequently encountered in aerosols. Under hazy conditions, S-rich particles coated with organic matter (S-OM particles) accounted for most of the total particles (15% to 24%), followed by soot particles (18% to 21%), organic particles (17% to 21%), non-mixed S-rich particles (10% to 18%), and S-rich particles with soot-, mineral-, or metal-inclusions (here referred to as S-inclusion particles) (11% to 15%). Under clear conditions, non-mixed S-rich and organic particles were dominant components, while mineral and soot particles were secondary components, among which, ~14% of the total particles had a sulfate core or OM coating; inclusions of mixture particles were often mixed with sulfate cores. In the sulfate core–OM shell structure particles, the ratio of core diameter to the whole particle diameter was ~0.52 under hazy conditions and ~0.60 under clear conditions, indicating a substantial sulfate and organic formation on the particles. Soot particles accounted for 18% to 21% of the total particles. The relative growth of aged soot particles was higher under hazy conditions than under clear conditions. In sum, particles from traffic emissions on a main urban road aged with the formation of sulfate and organic matter.

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An Investigation on Morphology and Fractal Dimension of Diesel and Diesel‑Biodiesel Soot Agglomerates

Cited by 3 publications

References 46 publications

Optical properties of coated black carbon aggregates: numerical simulations, radiative forcing estimates, and size-resolved parameterization scheme

Optical properties of coated black carbon aggregates: numerical simulations, radiative forcing estimates, and size-resolved parameterization scheme

In vitro Evaluation of Oxidative Stress Caused by Fine Particles (PM2.5) Exhausted from Heavy-Duty Vehicles Using Diesel/Biodiesel Blends under Real World Conditions

Characteristics and Aging of Traffic-Emitted Particles with Sulfate and Organic Compound Formation in Urban Air

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