Characterising Mass-resolved Mixing State of Black Carbon in Beijing Using a Morphology-Independent Measurement Method

Abstract. Refractory Black Carbon (rBC) in the atmosphere is known for its significant impact on the climate system in the atmosphere. The relationship between the microphysical and optical properties of rBC remain uncertain and are largely influenced by the size, coating thickness and mixing state of particles. This study presents a coupling of a centrifugal particle mass analyser (CPMA) and a single particle soot photometer (SP2) for the morphology-independent quantification of the mixing state of rBC-containing particles, used in the urban site of Beijing as part of the Air Pollution and Human Health-Beijing (APHH-Beijing) project during winter (10th Nov–10th Dec) and summer (18th May–25th June). An inversion method is applied to the measurements to present a two-variable distribution of both rBC core mass and total mass of rBC-containing particles and present the mass-resolved mixing state of rBC-containing particles. The mass ratio between non-rBC coating and rBC core (MR) is calculated to determine the coating thickness of the rBC-containing particles. The bulk MR was found to vary between 2–12 in winter and between 2–3 in summer. This mass-resolved mixing state is used to derive the mixing state index (χ) for the rBC-containing particles. χ quantifies whether the coating is evenly distributed across the rBC-containing particle population and is used to determine the degree of internal and external mixture of rBC-containing particles. The rBC-containing particles in Beijing were found to be 55%–70 % internally mixed in winter depending on the dominant air masses. χ of rBC-containing particles was highly positively associated with increased bulk MR, rBC mass loading or pollution level in winter, whereas χ of rBC-containing particles in summer varied significantly (ranging 60 %–75 %) within the narrowly-distributed bulk MR and was found to be independent of air mass sources. This concludes that the bulk MR may only act as a predictor of mixing state in winter, and χ is better to quantify the mixing state of rBC-containing particles. The same level of bulk MR corresponded with a higher χ in summer than in winter and this tended to suggest a limited formation of coatings on rBC largely depended on primary sources. However, with the higher Non-refractory PM1 (NR-PM1) concentration in winter, the coagulation process may still lead relative thick coatings. In summer the higher secondary compounds made the rBC-containing particles more homogeneous. But due to the higher temperatures and limited pollution level, the coating thickness in summer is limited. The mixing state of rBC-containing particles should also depend on the coating formation mechanism, both primary source influence and secondary coating formation mechanism should be considered in interpreting the rBC-containing particles mixing state in the atmosphere. This particle morphology-independent and mass-based data format as introduced in this study could be conviently applied in particle-resolved or other process models to investigate atmospheric rBC aging and mixing state properties.

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Characterising mass-resolved mixing state of black carbon in Beijing using a morphology-independent measurement method

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-3645-2020 ◽

2020 ◽

Vol 20 (6) ◽

pp. 3645-3661 ◽

Cited By ~ 3

Author(s):

Chenjie Yu ◽

Dantong Liu ◽

Kurtis Broda ◽

Rutambhara Joshi ◽

Jason Olfert ◽

...

Keyword(s):

Black Carbon ◽

Atmospheric Aerosols ◽

Particle Morphology ◽

Urban Site ◽

Inversion Method ◽

Mixing State ◽

State Index ◽

Cloud Scavenging ◽

Highly Correlated ◽

State Mixing

Abstract. Refractory black carbon (rBC) in the atmosphere is known for its significant impacts on climate. The relationship between the microphysical and optical properties of rBC remains poorly understood and is influenced by its size and mixing state. Mixing state also influences its cloud scavenging potential and thus atmospheric lifetime. This study presents a coupling of a centrifugal particle mass analyser (CPMA) and a single-particle soot photometer (SP2) for the morphology-independent quantification of the mixing state of rBC-containing particles, used in the urban site of Beijing as part of the Air Pollution and Human Health–Beijing (APHH-Beijing) project during winter (10 November–10 December 2016) and summer (18 May–25 June 2017). This represents a highly dynamic polluted environment with a wide variety of conditions that could be considered representative of megacity area sources in Asia. An inversion method (used for the first time on atmospheric aerosols) is applied to the measurements to present two-variable distributions of both rBC mass and total mass of rBC-containing particles and calculate the mass-resolved mixing state of rBC-containing particles, using previously published metrics. The mass ratio between non-rBC material and rBC material (MR) is calculated to determine the thickness of a hypothetical coating if the rBC and other material followed a concentric sphere model (the equivalent coating thickness). The bulk MR (MRbulk) was found to vary between 2 and 12 in winter and between 2 and 3 in summer. This mass-resolved mixing state is used to derive the mass-weighted mixing state index for the rBC-containing particles (χrBC). χrBC quantifies how uniformly the non-rBC material is distributed across the rBC-containing-particle population, with 100 % representing uniform mixing. The χrBC in Beijing varied between 55 % and 70 % in winter depending on the dominant air masses, and χrBC was highly correlated with increased MRbulk and PM1 mass concentration in winter, whereas χrBC in summer varied significantly (ranging 60 %–75 %) within the narrowly distributed MRbulk and was found to be independent of air mass sources. In some model treatments, it is assumed that more atmospheric ageing causes the BC to tend towards a more homogeneous mixture, but this leads to the conclusion that the MRbulk may only act as a predictor of χrBC in winter. The particle morphology-independent and mass-based information on BC mixing used in this and future studies can be applied to mixing-state-aware models investigating atmospheric rBC ageing.

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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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Size distribution and coating thickness of black carbon from the Canadian oil sands operations

10.5194/acp-2017-1015 ◽

2017 ◽

Author(s):

Yuan Cheng ◽

Shao-Meng Li ◽

Mark Gordon ◽

Peter Liu

Keyword(s):

Size Distribution ◽

Black Carbon ◽

Coating Thickness ◽

Oil Sands ◽

Radiative Forcing ◽

Climate Models ◽

Source Area ◽

Size Distributions ◽

Mixing State ◽

Earth’S Climate

Abstract. Black carbon (BC) plays an important role in the Earth’s climate system. However, parameterization of BC size and mixing state have not been well addressed in aerosol-climate models, introducing substantial uncertainties into the estimation of radiative forcing by BC. In this study, we focused on BC emissions from the massive oil sands (OS) industry in northern Alberta, based on an aircraft campaign conducted over the Athabasca OS region in 2013. A total of 14 flights were made over the OS source area, in which the aircraft was typically flown in a 4- or 5-sided polygon pattern along flight tracks encircling an OS facility. Another 3 flights were performed downwind of the OS source area, each of which involved at least three intercepting locations where the well-mixed OS plume was measured along flight tracks perpendicular to the wind direction. Comparable size distributions were observed for refractory black carbon (rBC) over and downwind of the OS facilities, with rBC mass median diameters (MMD) between ~ 135 and 145 nm that were characteristic of fresh urban emissions. This MMD range corresponded to rBC number median diameters (NMD) of ~ 60–70 nm, approximately 100 % higher than the NMD settings in some aerosol-climate models. The typical in- and out-of-plume segments of a flight, which had different rBC concentrations and photochemical ages, showed consistent rBC size distributions. Moreover, rBC size distributions remained unchanged at different downwind distances from the source area, suggesting that atmospheric aging would not necessarily change rBC size distribution. However, aging indeed influenced rBC mixing state. Coating thickness for rBC cores in the diameter range of 130–160 nm was nearly doubled within three hours when the OS plume was transported over a distance of 90 km from the source area.

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Design of Magnesia–Spinel Bricks for Improved Coating Adherence in Cement Rotary Kilns

Ceramics ◽

10.3390/ceramics4040046 ◽

2021 ◽

Vol 4 (4) ◽

pp. 652-666

Author(s):

Graziella Rajão Cota Pacheco ◽

Geraldo Eduardo Gonçalves ◽

Vanessa de Freitas Cunha Lins

Keyword(s):

Formation Mechanism ◽

Firing Temperature ◽

Essential Role ◽

Refractory Lining ◽

Refractory Structure ◽

Prolonged Operation ◽

Magnesia Spinel ◽

Coating Formation ◽

Rotary Kilns ◽

Coating Formation Mechanism

It is well known that doloma bricks present better coating adherence than magnesia–spinel bricks when applied in cement rotary kilns, which is related to the different coating formation mechanism. The coating has an essential role in prolonged operation by protecting the refractory lining; thus, it is important to improve its adherence on magnesia–spinel refractories. The objective of this investigation is to study different compositions of magnesia–spinel bricks, achieved by varying additives used (calcined alumina, limestone, hematite and zirconia) and firing temperature (1500 °C and 1700 °C), to enhance the coating adherence measured by the sandwich test. The results have pointed out that the use of higher firing temperature contributes positively to physical adherence due to well-sintered refractory structure and elevated permeability, attaining coating strength superior to 2 MPa. For the chemical adherence, the addition of 2 wt.% of limestone increased the coating strength to 3 MPa, but resulted in a drop in hot properties. In this context, the most suitable approach to improve adherence of clinker coating and maintain hot properties in suitable levels is to increase the firing temperature.

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Influences of Primary Emission and Secondary Coating Formation on the Particle Diversity and Mixing State of Black Carbon Particles

Environmental Science & Technology ◽

10.1021/acs.est.9b03064 ◽

2019 ◽

Vol 53 (16) ◽

pp. 9429-9438 ◽

Cited By ~ 2

Author(s):

Alex K.Y. Lee ◽

Laura-Hélèna Rivellini ◽

Chia-Li Chen ◽

Jun Liu ◽

Derek J. Price ◽

...

Keyword(s):

Black Carbon ◽

Mixing State ◽

Carbon Particles ◽

Coating Formation

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

10.5194/acp-2019-244 ◽

2019 ◽

Cited By ~ 2

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.

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Adhesion Phenomenon of Titanium as Cathode in Aluminum Anodizing

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.799-800.140 ◽

2015 ◽

Vol 799-800 ◽

pp. 140-144 ◽

Cited By ~ 2

Author(s):

Putu Hadi Setyarini ◽

Rudy Soenoko ◽

Agus Suprapto ◽

Yudy Surya Irawan

Keyword(s):

Formation Mechanism ◽

Electric Potential ◽

Film Coating ◽

Titanium Content ◽

Deposition Surface ◽

Coating Formation ◽

Coating Formation Mechanism ◽

Aluminum Anodizing

This paper discusses the film coating formation mechanism after an anodizing process carried out in AA6061 with a varying potential between 15-30V. The electrolyte used to be 1M H3PO4with titanium as the cathode. From this study, it was found that after the anodizing process the pore uniformity occurs with a size varied from 1.09-5.74 μm become 2.78-4.56 μm. There was also an increase in the titanium content on the deposition surface about 21% and was achieved at an electric potential of 25V where titanium in the pore penetration occurs up to the depth of 5 μm.

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Characterizing the evolution of physical properties and mixing state of black carbon particles: from near a major highway to the broader urban plume in Los Angeles

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-11991-2018 ◽

2018 ◽

Vol 18 (16) ◽

pp. 11991-12010 ◽

Cited By ~ 3

Author(s):

Trevor S. Krasowsky ◽

Gavin R. McMeeking ◽

Constantinos Sioutas ◽

George Ban-Weiss

Keyword(s):

Los Angeles ◽

Physical Properties ◽

Black Carbon ◽

Coating Thickness ◽

Global Climate ◽

Weekend Effect ◽

Mixing State ◽

Measured Distance ◽

Urban Plume ◽

Thick Coatings

Abstract. Black carbon (BC) particles can have deleterious human health consequences and impact regional and global climate. Uncertainties remain in part due to incomplete knowledge on the evolution of physical properties and mixing state of black carbon from sources to the remote atmosphere. We aim to understand how “road-to-ambient” processing and longer timescale aging in an urban plume affect black carbon physical properties. Refractory black carbon (rBC) was measured during summer 2016 using a single-particle soot photometer (SP2) in two distinct environments: near a major freeway and downwind of downtown Los Angeles. The near-road measurements were made at distances ranging from 30 to 114 m downwind of Interstate 405 in Los Angeles. These results were compared with measurements performed 100 km east of Los Angeles in Redlands, California. Coatings on rBC particles were quantified using two methods. As distance from the highway increased at the near-road site, we observed decreases in rBC mass and number concentrations and increases in the number fraction of rBC particles with thick coatings (f). The latter likely occurred due to rapid processing of the highway plume and entrainment of urban background particles. Most rBC-containing particles measured near the highway were either uncoated or thinly coated. In Redlands, we found that rBC mass concentrations on weekdays were similar to those observed at the furthest measured distance from the highway (114 m). However, rBC number concentrations for the smallest measured sizes were an order of magnitude lower in Redlands than all measured distances from the highway. Observations of f indicate that values in Redlands during periods when estimated photochemical age (PCA) was highest (6–8 h) were similar to corresponding values at the furthest measured distance from the highway. This suggests that the residence time of air in the Los Angeles Basin under typical summertime conditions measured during this campaign may not be sufficient for rBC to acquire thick coatings. However, under certain meteorological conditions, f was observed to be ∼0.20 in Redlands, with coating thickness histograms showing a larger contribution of rBC particles with coating thickness > 80 nm. This occurred during a weekend day when local emissions from diesel vehicles were lower (compared to weekdays) and winds brought air from the desert regions to Redlands, both of which would increase the relative contribution of remote sources of rBC. Afternoon values of f (and O3) were found to be systematically higher on weekends than weekdays, suggesting that the “weekend effect” can create more thickly coated rBC particles presumably due to enhanced secondary organic aerosol (SOA) and reduced available rBC as condensation sites.

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Morphology and mixing of black carbon particles collected in central California during the CARES field study

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-14515-2016 ◽

2016 ◽

Vol 16 (22) ◽

pp. 14515-14525 ◽

Cited By ~ 29

Author(s):

Ryan C. Moffet ◽

Rachel E. O'Brien ◽

Peter A. Alpert ◽

Stephen T. Kelly ◽

Don Q. Pham ◽

...

Keyword(s):

Black Carbon ◽

Central Valley ◽

Photochemical Activity ◽

Urban Site ◽

Mixing State ◽

Data Set ◽

Carbon Particles ◽

Aerosol Absorption ◽

Scanning Transmission ◽

Rural Sites

Abstract. Aerosol absorption is strongly dependent on the internal heterogeneity (mixing state) and morphology of individual particles containing black carbon (BC) and other non-absorbing species. Here, we examine an extensive microscopic data set collected in the California Central Valley during the CARES 2010 field campaign. During a period of high photochemical activity and pollution buildup, the particle mixing state and morphology were characterized using scanning transmission X-ray microscopy (STXM) at the carbon K-edge. Observations of compacted BC core morphologies and thick organic coatings at both urban and rural sites provide evidence of the aged nature of particles, highlighting the importance of highly aged particles at urban sites during periods of high photochemical activity. Based on the observation of thick coatings and more convex BC inclusion morphology, either the aging was rapid or the contribution of fresh BC emissions at the urban site was relatively small compared to background concentrations. Most particles were observed to have the BC inclusion close to the center of the host. However, host particles containing inorganic rich inclusions had the BC inclusion closer to the edge of the particle. These measurements of BC morphology and mixing state provide important constraints for the morphological effects on BC optical properties expected in aged urban plumes.

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