Characteristics of black carbon aerosol in Jiaxing,China during autumn 2013

We conducted measurements of black carbon (BC) aerosol in Jiaxing, China during autumn from September 26 to November 30, 2013. We investigated temporal and diurnal variations of BC, and its correlations with meteorological parameters and other major pollutants. Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m³, with an average of 5.1 μg/m³. The diurnal variation of BC exhibited a bimodal distribution, with peaks at 07:00 and 18:00. The morning peak was larger than the evening peak. The mass percentages of BC in PM_2.5 and PM₁₀ were 7.1% and 4.8%, respectively. The absorption coefficient of BC was calculated to be 44.4 Mm⁻¹, which accounted for 11.1% of the total aerosol extinction. BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m³ during the measurement period. Correlation analysis indicated that the main sources of BC were motor vehicle exhaust, and domestic and industrial combustion.     

Characteristics of elemental carbon and organic carbon in PM10 during spring and autumn in Chongqing, China

PM10 （particulate matter with aerodynamic diameter less than 10 μm） samples were collected simultaneously at nine urban sites and one urban background site during two intensive observation campaigns in 2006. Concentrations of elemental carbon （EC） and organic carbon （OC） in PM10 were analyzed using an element analyzer. The characteristics regarding spatial and seasonal distribution patterns of OC and EC concentrations and their contributions to PM10 mass, as well as correlation between OC and EC, were investigated in detail. The average OC and EC concentrations for urban sites were 57.5 ± 20.8 and 8.3 ± 3.9 μg/m^3, respectively, both being around three times higher than those for urban background site. As a whole, EC concentrations did not show distinct seasonal variations, though OC concentrations were generally higher in autumn than in spring. For urban sites, total carbonaceous aerosol （TCA） accounted for 33.2% in spring and 35.0% in autumn of PM10 mass. The OC and EC concentrations were found significantly correlated to each other both in spring and in autumn, implying the existence of similar emission sources such as coal combustion. The OC/EC ratios generally exceeded 2.0, indicating the presence of secondary organic carbon （SOC）, whose estimated concentration for urban Chongqing was 26.7 and 39.4μg/m^3, accounting for 48.9 and 61.9% of the total OC observed in the samples, in spring and in autumn, respectively.     

Possible effects of climate change of wind on aerosol variation during winter in Shanghai,China

Several data sets were introduced to investigate the possible effects of climate-change-related variation of wind on aerosol concentration during winter in Shanghai,China.These data sets included the daily wind speed,wind direction,visibility,and precipitation from "1956 to 2010,hourly PM₁₀ concentration from 2008 to 2010,and the NCEP/NCAR reanalysis data of global atmospheric circulation from 1956 to2010.The trend of aerosol concentration and its correlations with wind speed and wind direction in winter were analyzed.Results indicated that there was an increase in the number of haze days in winter of 2.1 days/decade.Aerosol concentration,represented by PM₁₀ in this study,was highly correlated to both wind speed and direction in winter.The PM₁₀ concentration increased as wind speed decreased,reaching maximum values under static wind conditions.The PM₁₀ concentration was relatively lower under easterly winds and higher under westerly winds.The analysis showed that weaker East Asia winter monsoons have resulted in a reduction of wind speed,increase in static wind frequency,and decline in the frequency of northerly winds since the 1980 s.Moreover,the rapid expansion of urban construction in Shanghai has changed the underlying surface considerably,which has led to a reduction in wind speed.Finally,a wind factor was defined to estimate the combined effects of wind speed and wind direction on aerosol concentrations in Shanghai.The analysis of this factor indicated that changes in atmosphere circulation and urbanization have had important effects on the number of winter haze days in Shanghai.     

Possible effects of climate change of wind on aerosol variation during winter in Shanghai,China

Several data sets were introduced to investigate the possible effects of climate-change-related variation of wind on aerosol concentration during winter in Shanghai, China. These data sets included the daily wind speed, wind direction, visibility, and precipitation from 1956 to 2010, hourly PM₁₀ concentration from 2008 to 2010, and the NCEP/NCAR reanalysis data of global atmospheric circulation from 1956 to 2010. The trend of aerosol concentration and its correlations with wind speed and wind direction in winter were analyzed. Results indicated that there was an increase in the number of haze days in winter of 2.1 days/decade. Aerosol concentration, represented by PM₁₀ in this study, was highly correlated to both wind speed and direction in winter. The PM₁₀ concentration increased as wind speed decreased, reaching maximum values under static wind conditions. The PM₁₀ concentration was relatively lower under easterly winds and higher under westerly winds. The analysis showed that weaker East Asia winter monsoons have resulted in a reduction of wind speed, increase in static wind frequency, and decline in the frequency of northerly winds since the 1980s. Moreover, the rapid expansion of urban construction in Shanghai has changed the underlying surface considerably, which has led to a reduction in wind speed. Finally, a wind factor was defined to estimate the combined effects of wind speed and wind direction on aerosol concentrations in Shanghai. The analysis of this factor indicated that changes in atmosphere circulation and urbanization have had important effects on the number of winter haze days in Shanghai.     

Light attenuation cross-section of black carbon in an urban atmosphere in northern China

Fine particulate matter(PM_2.5) samples were collected over two years in Xi’an,China to investigate the relationships between the aerosol composition and the light absorption efficiency of black carbon（BC）.Real-time light attenuation of BC at 880 nm was measured with an aethalometer.The mass concentrations and elemental carbon（EC） contents of PM_2.5 were obtained,and light attenuation cross-sections(σ_ATN)of PM_2.5 BC were derived.The mass of EC contributed ⁵% to PM2.5 on average.BC σ_ATN exhibited pronounced seasonal variability with values averaging 18.6,24.2,16.4,and 26.0 m²/g for the spring,summer,autumn,and winter,respectively,while averaging 23.0 m²/g overall.σ_ATN varied inversely with the ratios of EC/PM_2.5,EC/[SC₄^2-],and EC/[NO₃^-].This study of the variability in σ_ATN illustrates the complexity of the interactions among the aerosol constituents in northern China and documents certain effects of the high EC,dust,sulfate and nitrate loadings on light attenuation.     

Light attenuation cross-section of black carbon in an urban atmosphere in northern China

Fine particulate matter (PM_2.5) samples were collected over two years in Xi’an, China to investigate the relationships between the aerosol composition and the light absorption efficiency of black carbon (BC). Real-time light attenuation of BC at 880 nm was measured with an aethalometer. The mass concentrations and elemental carbon (EC) contents of PM_2.5 were obtained, and light attenuation cross-sections (σ_ATN) of PM_2.5 BC were derived. The mass of EC contributed ∼5% to PM_2.5 on average. BC σ_ATN exhibited pronounced seasonal variability with values averaging 18.6, 24.2, 16.4, and 26.0 m²/g for the spring, summer, autumn, and winter, respectively, while averaging 23.0 m²/g overall. σ_ATN varied inversely with the ratios of EC/PM_2.5, EC/[SO₄²⁻], and EC/[NO₃⁻]. This study of the variability in σ_ATN illustrates the complexity of the interactions among the aerosol constituents in northern China and documents certain effects of the high EC, dust, sulfate and nitrate loadings on light attenuation.     

Characteristics of organic and elemental carbon in atmospheric fine particles in Tianjin, China

PM2.5 samples were collected at urban, industrial and coastal sites in Tianjin during winter, spring and summer in 2007. Concentrations of elemental carbon （EC） and organic carbon （OC） were analyzed using the IMPROVE thermal-optical reflectance （TOR） method. Both OC and EC exhibited a clear seasonal pattern with higher concentrations observed in the winter than in the spring and summer, due to cooperative effect of changes in emission rates and seasonal meteorology. The concentrations of carbonaceous species were also influenced by the local factors at different sampling sites, ranking in the order of industrial〉 urban 〉 coastal during winter and spring. In the summer, the port emissions, enriched with EC, had a significant impact on carbonaceous aerosols at the coastal site. Total carbonaceous aerosol accounted for 40.0% in winter, 33.8% in spring and 31.4% in summer of PM2.5 mass. Good correlation （R = 0.84-0.93） between OC and EC indicated that they had common dominant sources of combustion such as coal burning and traffic emissions. The daily average OC/EC ratios ranged from 2.1 to 9.1, the elevated OC/EC ratios being found in the winter. The estimated secondary organic carbon （SOC） accounted for 46.9%, 35.3% and 40.2% of the total OC in the winter, spring and summer, respectively, indicating that SOC may be an important contributor to fine organic aerosol in Tianjin.     

Aerosol optical absorption by dust and black carbon in Taklimakan Desert,during no-dust and dust-storm conditions

Aerosol absorption coefficient σ_ap involves the additive contribution of both black carbon aerosol (BC) and dust aerosol. The linear statistical regression analysis approach introduced by Fialho et al. (2005) is used to estimate the absorption exponents of BC and dust aerosol absorption coefficients, and further to separate the contributions of these two types of aerosols from the total light absorption coefficient measured in the hinterland of Taklimakan Desert in the spring of 2006. Absorption coefficients are measured by means of a 7-wavelength Aethalometer from 1 March to 31 May and from 1 November to 28 December, 2006. The absorption exponent of BC absorption coefficient α is estimated as (?0.95 ± 0.002) under background weather (supposing the observed absorption coefficient is due only to BC); the estimated absorption exponent of dust aerosol absorption coefficient β during the 6 dust storm periods (strong dust storm) is (?2.55 ± 0.009). Decoupling analysis of the measured light absorption coefficients demonstrates that, on average, the light absorptions caused by dust aerosol and BC make up about 50.5% and 49.5% respectively of the total light absorption at 520 nm; during dust weather process periods (dust storm, floating dust, blowing dust), the contribution of dust aerosol to absorption extinction is 60.6% on average; in the hinterland of desert in spring, dust aerosol is also the major contributor to the total aerosol light absorption, more than that of black carbon aerosol.     

Comparison of aerosol characteristics during haze periods over two urban agglomerations in China using CALIPSO observations

Using CALIPSO (cloud-aerosol lidar and infrared pathfinder satellite observation) vertical observation data during haze periods from January 2007 to December 2008, we analyzed differences in aerosol characteristics near the surface, as well as in the middle troposphere between the Beijing–Tianjin–Hebei metropolitan region (Area A) and the Yangtze River Delta region (Area B) in China. One significant difference was that haze pollution in Area A was related to local and non-local aerosols, while in Area B it was related to local anthropogenic sources. In all seasons apart from autumn, aerosol pollution in Area A was more severe than in Area B, both near the surface and at higher altitudes. In Area A, non-spherical aerosols were dominant from 0 to 4 km in spring, summer, and winter; while in autumn, there were considerably high numbers of non-spherical aerosols below 0.5 km, and near-spherical aerosols from 0.5 to 4 km. In Area B, both near-spherical and non-spherical aerosols were common in all seasons. Moreover, aerosols with attenuated color ratios of 0–0.2 were more common in all seasons in Area A than in Area B, indicating that fine particle pollution in Area A was more serious than in Area B. Finally, relatively large aerosols linked to gravity settling appeared more frequently near the surface in Area A than in Area B.     

Mixing state of individual carbonaceous particles during a severe haze episode in January 2013,Nanjing,China

Chemical composition,hourly counts,and sizes of atmospheric carbonaceous particles were measured to investigate their mixing state on clear and hazy days.623,122 carbonaceous particles with sizes0.2-2.0 μm was analyzed using a single-particle aerosol mass spectrometer from 1st to 17 th January2013.Particle types included biomass/biofuel burning particles(biomass),element carbon(EC-dominant)particles that were also mixed with biomass/biofuel burning species(EC-biomass) or secondary species(EC-secondary),organic carbon(OC),internally mixed OC and EC(OCEC),ammonium-containing(ammonium) and sodium-containing(sodium) particles.On clear days the top ranked carbonaceous particle types were biomass(48.2%),EC-biomass(15.7%),OCEC(11.1%),and sodium(9.6%),while on hazy days they were biomass(37.3%),EC-biomass(17.6%),EC-secondary(16.6%),and sodium(12.7%).The fractions of EC-secondary,ammonium(10%),and sodium particle types were elevated on hazy days.Numbers of EC-secondary particles were more than four times those on clear days(4.1%).Thus,carbonaceous particles mixed with ammonium,nitrate and sulfate during aging and transport,enhancing their light extinction effects and hygroscopic growth under high relative humidity on hazy days,further reducing visibility.Our real-time single-particle data showed that changes to mixing state had a significant impact on light extinction during haze events in Nanjing.     

Mixing state of individual carbonaceous particles during a severe haze episode in January 2013, Nanjing,China

Chemical composition, hourly counts, and sizes of atmospheric carbonaceous particles were measured to investigate their mixing state on clear and hazy days. 623,122 carbonaceous particles with sizes 0.2–2.0 μm was analyzed using a single-particle aerosol mass spectrometer from 1st to 17th January 2013. Particle types included biomass/biofuel burning particles (biomass), element carbon (EC-dominant) particles that were also mixed with biomass/biofuel burning species (EC-biomass) or secondary species (EC-secondary), organic carbon (OC), internally mixed OC and EC (OCEC), ammonium-containing (ammonium) and sodium-containing (sodium) particles. On clear days the top ranked carbonaceous particle types were biomass (48.2%), EC-biomass (15.7%), OCEC (11.1%), and sodium (9.6%), while on hazy days they were biomass (37.3%), EC-biomass (17.6%), EC-secondary (16.6%), and sodium (12.7%). The fractions of EC-secondary, ammonium (10%), and sodium particle types were elevated on hazy days. Numbers of EC-secondary particles were more than four times those on clear days (4.1%). Thus, carbonaceous particles mixed with ammonium, nitrate and sulfate during aging and transport, enhancing their light extinction effects and hygroscopic growth under high relative humidity on hazy days, further reducing visibility. Our real-time single-particle data showed that changes to mixing state had a significant impact on light extinction during haze events in Nanjing.     

Impacts of aerosol chemical compositions on optical properties in urban Beijing,China

The optical properties of aerosols and their chemical composition,including water-soluble ions,organic carbon（OC）,and elemental carbon（EC） in PM_2.5 and PM₁₀,were measured from 26 May to 30 June of 2012 at an urban site in Beijing.The daily average concentrations of PM_2.5 and PM₁₀ were 103.2 and 159.6 μg/m³,respectively.On average,the OC and EC contributed 20.1% and 4.3% ,respectively,to PM_2.5 and 16.3% and3.9% ,respectively,to PM₁₀.Secondary ions(SO₄^2-,NO₃^-,and NH₄⁺) dominated the water-soluble ions and accounted for 57.9% and 62.6% of PM_2.5 and PM₁₀,respectively.The wind dependence of PM_2.5,OC,SO₄^2-,and NO₃^- implied that the pollution sources mainly came from south and southeast of Beijing during the summer.The monthly mean values of the scattering coefficient(σ_sc) and absorption coefficient(σ_ab) at525 nm were 312.9 and 28.7 Mm^-1,respectively,and the mean single-scattering albedo（ω） was 0.85.The wind dependence of σ_sc revealed that this value was mainly influenced by regional transport during the summer,and the relationship between σ_ab and wind indicated that a high σ_ab resulted from the joint effects of local emissions and regional transport.The reconstructed σ_sc that was derived from the revised IMPROVE equation agreed well with the observations.The contribution of different chemical species toσ_sc was investigated under different pollution levels,and it was found that secondary inorganic aerosols accounted for a large part of σ_sc during pollution episodes（35.7% ）,while organic matter was the main contributor to σ_sc under clean conditions（33.6% ）.     

The glass transition in carbon black reinforced rubber

Summary It can be stated that the influence of the presence of carbon black in a rubber vulcanisate with regard to the dynamic properties can be explained by assuming physical adsorption of rubber on the black surface. The effect can be represented by assuming an adsorbed layer having different properties from the bulk rubber taking the layer thickness to be at least 20 Å. Adsorption — desorption from this layer causes non-linearity and may contribute to the losses observed in the rubber-glass transition. This adsorption is analogous to the adsorption of simple liquids in microporous systems such as silicagel and activated carbon.     

Rheology of dispersant-free aqueous slurries of carbon black

The rheological characteristics of dispersant-free aqueous slurries of carbon blacks have been studied over a range of concentrations of 4 to 18%. Single pass measurements were carried out with a falling plunger viscometer in order to determine as nearly as possible, the properties of the undisturbed slurries. The slurries exhibit plastic or pseudoplastic flow behavior but are extremely sensitive to conditions of preparation. Slurries can be thickened by the application of high shear and thinned by the application of low shear. These changes are not spontaneously reversible on standing. The rheology of slurries of different carbon blacks depends on their particle size, structure, and surface chemistry. These results are interpreted in terms of a model involving small anisometric aggregates which can associate to form either a network or else a system of large, spherical flocs.

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Zusammenfassung Die rheologischen Eigenschaften von dispersionsmittelfreien wäßrigen Rußschlämmen wurden über einen weiten Konzentrationsbereich von 4 bis 18% untersucht. Um so nahe wie möglich die Eigenschaften der ungestörten Schlämme zu erfassen, wurden einmalige Messungen mit einem Fallzylinderviskosimeter vomLawaczek-Typ ausgeführt. Die Schlämme, die ein plastisches oder pseudoplastisches bzw. strukturviskoses Fließverhalten aufweisen, sind höchst empfindlich gegenüber der Art der Vorbereitung.Die Schlämme können durch Anwendung hoher Scherbeanspruchung eine Viskositätserhöhung zeigen und wider Erwarten durch geringe Scherbeanspruchung eine Viskositätserniedrigung. Diese Änderungen sind beim Stehen nicht spontan reversibel. Es wird dargestellt, daß die Rheologie der Schlämme verschiedener Rußarten von ihrer Teilchengröße, ihrer Struktur und den chemischen Oberflächeneigenschaften abhängt.Diese Ergebnisse werden interpretiert mittels einer Modellvorstellung, die kleine anisometrische Aggregate voraussetzt, welche zu einem Netzwerk assoziieren oder irgendein System von großen kugelförmigen Flocken bilden können.

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Presented at the Southwest-Southeast Regional Meeting of the American Chemical Society (December 7–9, 1961, New Orleans, La.).     

Modeling study of a severe aerosol pollution event in December 2013over Shanghai China:An application of chemical data assimilation

This study focuses on the importance of initial conditions to air-quality predictions.We ran assimilation experiments using the WRF-Chem model and grid-point statistical interpolation(GSI),for a 9-day severe particulate matter pollution event that occurred in Shanghai in December 2013.In this application,GSI used a three-dimensional variational approach to assimilate ground-based PM2.5 observations into the chemical model,to obtain initial fields for the aerosol species.In our results,data assimilation significantly reduced the errors when compared to a simulation without assimilation,and improved forecasts of PM_(2.5)concentrations.Despite a drop in skill directly after the assimilation,a positive effect was present in forecasts for at least 12-24 h,and there was a slight improvement in the 48-h forecasts.In addition to performing well in Shanghai,the verification statistics for this assimilation experiment are encouraging for most of the surface stations in China.     

Dependence of flow behaviour on carbon black distribution in polyblend systems

The flow behaviour of four blend systems was determined at four shear rates and three processing temperatures using an extrusion rheometer. The blends were based on natural rubber/polybutadiene elastomers and were prepared using various mixing sequences with the carbon black being added in different ways.The degree of die swelling was found to depend on the blending technique, the processing temperature and the extrusion rate. A theoretical model was used to calculate the stored elastic energy, shear modulus and relaxation time. Melt fracture was observed when the carbon black was premixed in just one component of the blend.     

Seasonal variations and sources of mass and chemical composition for PM10 aerosol in Hangzhou,China

Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM10 mass, 22 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Cd, Ba, and Pb), 5 major ions (F-, Cl-, NO3-, SO42-, and NH4+), and organic and elemental carbon (OC and EC), showing that PM10 mass ranged from 46.7 to 270.8 μg/m3, with an annual average of 119.2 μg/m3. Na, AI, Si, S. K, Ca, and Fe were the most abundant elements in PM10, most ors being in the form of SO42-. SO42-, NO4-, and NH4+ were the major ions, which contributed to about 20%; of the PM10 mass. The mean seasonal concentrations for SO42- , averaged over all sites, were found to be 18.0, 18.5, 24.Z and 21.4 μg/m3. for spring, summer, autumn, and winter, respectively, while the corresponding Ioadings for NO3- were 72, 4.7, 7.1, and 11.2μg/m3. and for NH4+ were 6.0, 5.9, 8.2. and 9.3 μg/m3, in the form mostly of NH4NO3 in spring, autumn, and winter, and mostly of (NH4)2SO4 in summer. The low NO3-/SO42- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM10 were found to be 21A, and 4.1 μg/m3, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM10 for the four seasons, as is characteristic for cities in South China.     

Seasonal variations and sources of mass and chemical composition for PM10 aerosol in Hangzhou,China

Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM10 mass, 22 elements （Na, Mg, AI, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As. Se, Br, Cd, Ba, and Pb）, 5 major ions （F^-, Cl^ , NO3^-, SO4^2- , and NH4^＋）, and organic and elemental carbon （OC and EC）, showing that PM10 mass ranged from 46.7 to 270.8 μg/m^3, with an annual average of 119.2 μg/m^3. Na, AI, Si, S, K, Ca, and Fe were the most abundant elements in PM10, most of S being in the form of SO4^2- . SO4^2-, NO3^-, and NH4^＋ were the major ions, which contributed to about 20% of the PM10 mass. The mean seasonal concentrations for SO4^2- , averaged over all sites, were found to be 18.0, 18.5, 24,Z and 21.4 μg/m^3, for spring, summer, autumn, and winter, respectively, while the corresponding loadings for NO3^- were 7.2, 4.7, 7.1, and 11.2 μg/m^3, and for NH4^＋ were 6.0, 5.9, 8.2, and 9.3 μg/m^3, in the form mostly of NH4NO3 in spring, autumn, and winter, and mostly of （NH4）2SO4 in summer. The low NO3^-/SO4^2- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM10 were found to be 21.4, and 4.1 μg/m^3, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM10 for the four seasons, as is characteristic for cities in South China.