Impact of Gobi desert dust on aerosol chemistry of Xi'an, inland China during spring 2009: differences in composition and size distribution between the urban ground surface and the mountain atmosphere

Abstract. Composition and size distribution of atmospheric aerosols from Xi'an city (~400 m, altitude) in inland China during the spring of 2009 including a massive dust event on 24 April were measured and compared with a parallel measurement at the summit (2060 m, altitude) of Mt. Hua, an alpine site nearby Xi'an. EC, OC and major ions in the city were 2–22 times higher than those on the mountaintop during the whole sampling period. Sulfate was the highest species in the nonevent time in Xi'an and Mt. Hua, followed by nitrate, OC and NH4+. In contrast, OC was the most abundant in the event at both sites, followed by sulfate, nitrate and Ca2+. Compared to those on the urban ground surface aerosols in the elevated troposphere over Mt. Hua contain more sulfate and less nitrate, because HNO3 is formed faster than H2SO4 and thus long-range transport of HNO3 is less significant than that of H2SO4. An increased water-soluble organic nitrogen (WSON) was observed for the dust samples from Xi'an, indicating a significant deposition of anthropogenic WSON onto dust and/or an input of biogenic WSON from Gobi desert. As far as we know, it is for the first time to perform a simultaneous observation of aerosol chemistry between the ground surface and the free troposphere in inland East Asia. Our results showed that fine particles are more acidic on the mountaintop than on the urban ground surface in the nonevent, mainly due to continuous oxidation of SO2 to produce H2SO4 during the transport from lowland areas to the alpine atmosphere. However, we found the urban fine particles became more acidic in the event than in the nonevent, in contrast to the mountain atmosphere, where fine particles were less acidic when dust was present. The opposite changes in acidity of fine particles at both sites during the event are mostly caused by enhanced heterogeneous formation of nitrate onto dust in the urban air and decreased formation of nitrate in the mountain troposphere. In comparison to those during the nonevent Cl− and NO3− in the urban air during the event significantly shifted toward coarse particles. Such redistributions were further pronounced on the mountaintop when dust was present, resulting in both ions almost entirely staying in coarse particles. On the contrary, no significant spatial difference in size distribution of SO42− was found between the urban ground surface and the mountain atmosphere, dominating in the fine mode (<2.1 μm) during the nonevent and comparably distributing in the fine (<2.1 μm) and coarse (>2.1 μm) modes during the event.

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Impact of vehicular emissions on the formation of fine particles in the Sao Paulo Metropolitan Area: a numerical study with the WRF-Chem model

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-777-2016 ◽

2016 ◽

Vol 16 (2) ◽

pp. 777-797 ◽

Cited By ~ 29

Author(s):

A Vara-Vela ◽

M. F. Andrade ◽

P. Kumar ◽

R. Y. Ynoue ◽

A. G. Muñoz

Keyword(s):

Size Distribution ◽

Metropolitan Area ◽

Atmospheric Aerosols ◽

Fine Particles ◽

Sao Paulo ◽

Vehicular Emissions ◽

São Paulo ◽

Mass Size Distribution ◽

Mass Size ◽

The Impact

Abstract. The objective of this work is to evaluate the impact of vehicular emissions on the formation of fine particles (PM2.5; ≤  2.5 µm in diameter) in the Sao Paulo Metropolitan Area (SPMA) in Brazil, where ethanol is used intensively as a fuel in road vehicles. The Weather Research and Forecasting with Chemistry (WRF-Chem) model, which simulates feedbacks between meteorological variables and chemical species, is used as a photochemical modelling tool to describe the physico-chemical processes leading to the evolution of number and mass size distribution of particles through gas-to-particle conversion. A vehicular emission model based on statistical information of vehicular activity is applied to simulate vehicular emissions over the studied area. The simulation has been performed for a 1-month period (7 August–6 September 2012) to cover the availability of experimental data from the NUANCE-SPS (Narrowing the Uncertainties on Aerosol and Climate Changes in Sao Paulo State) project that aims to characterize emissions of atmospheric aerosols in the SPMA. The availability of experimental measurements of atmospheric aerosols and the application of the WRF-Chem model made it possible to represent some of the most important properties of fine particles in the SPMA such as the mass size distribution and chemical composition, besides allowing us to evaluate its formation potential through the gas-to-particle conversion processes. Results show that the emission of primary gases, mostly from vehicles, led to a production of secondary particles between 20 and 30 % in relation to the total mass concentration of PM2.5 in the downtown SPMA. Each of PM2.5 and primary natural aerosol (dust and sea salt) contributed with 40–50 % of the total PM10 (i.e. those ≤  10 µm in diameter) concentration. Over 40 % of the formation of fine particles, by mass, was due to the emission of hydrocarbons, mainly aromatics. Furthermore, an increase in the number of small particles impaired the ultraviolet radiation and induced a decrease in ozone formation. The ground-level O3 concentration decreased by about 2 % when the aerosol-radiation feedback is taken into account.

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The Role of Particle Size Distribution in the Performance and Modelling of Filtration

Water Science & Technology ◽

10.2166/wst.1993.0199 ◽

1993 ◽

Vol 27 (10) ◽

pp. 19-34 ◽

Cited By ~ 9

Author(s):

R. I. Mackie ◽

R. Bai

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Size Distribution ◽

Fine Particles ◽

Coarse Particles ◽

Large Particles

The paper examines the importance of size distribution of the influent suspension on the performance of deep bed filters and its significance with regard to modelling. Experiments were carried out under a variety of conditions using suspensions which were identical in every respect apart from their size distribution. The results indicate that the presence of coarse particles does increase the removal of fine particles. Deposition of fine particles leads to a greater headloss than deposition of large particles. Changes in size distribution with time and depth play an important role in determining the behaviour of a filter, and models of both removal and headloss development must take account of this.

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MPT Influence on the Rheological Behaviour of Self-Flow Refractory Castables

Materials Science Forum ◽

10.4028/www.scientific.net/msf.587-588.133 ◽

2008 ◽

Vol 587-588 ◽

pp. 133-137 ◽

Cited By ~ 5

Author(s):

Abílio P. Silva ◽

Ana M. Segadães ◽

Tessaleno C. Devezas

Keyword(s):

Particle Size ◽

Particle Size Distribution ◽

Mechanical Strength ◽

Size Distribution ◽

Fine Particles ◽

Rheological Behaviour ◽

Response Surfaces ◽

Coarse Particles ◽

Aggregate Particle ◽

Refractory Castables

The success of a refractory castable is largely due to the quality of its properties and ease of application. Self-flow refractory castables (SFRC), with high flowability index (>130%), can be easily accommodated in a mould without the application of external energy, being ideal for the manufacture of monolithic linings. SFRC castables without cement require a matrix of very fine particles, which guarantees improved rheological behaviour and performs the role of the binder in the absence of the refractory cement. The presence of the aggregate (coarse particles) hinders the flowability index, but improves the castable mechanical strength and reduces firing shrinkage, and also contributes to the reduction of the castable costs. The control of the maximum paste thickness (MPT) allows the reduction of the coarse particles interference, minimizing the number of contact points among the grains and avoiding the formation of an aggregate skeleton that impairs the flowability of the mixture. In the present work, 100% alumina SFRCs without cement were produced with a fixed matrix of fine particles, whose particle size distribution was optimized using statistical techniques (mixtures design and triangular response surfaces). Different aggregate particle size distributions were used, with several MPT values, with the objective of evaluating which was the mean distance that maximized the flowability index, simultaneously ensuring good mechanical strength for the refractory castable. Ensuring a minimum surface area of 2.22m2/g, the mixtures reach the self-flow turning point with a minimum water content and the maximum flowability is obtained for an aggregate particle size distribution modulus of q=0.22, and consequently an optimized MPT value. SFRC with high mechanical strength (>60MPa) were obtained.

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Size Characteristics of Sediments Eroded under Different Masson Pine Litter Covers in South China

Water ◽

10.3390/w13162190 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2190

Author(s):

Fangfang Zhu ◽

Yuchen Li ◽

Jinhua Cheng

Keyword(s):

Particle Size ◽

Soil Erosion ◽

Particle Size Distribution ◽

Size Distribution ◽

Fine Particles ◽

Enrichment Ratio ◽

Coarse Particles ◽

Characteristic Parameters ◽

Sediment Distribution ◽

The Relationship

The particle size distribution characteristics of runoff sediments are vital for understanding the effect of the mechanism of soil erosion on slopes. The objective of this study was to investigate the particle-size distribution of sediments eroded from slopes covered by different litter coverage masses under artificial rainfall simulation. Litter was spread on the surface of a soil tank according to different biomasses (0 g·m−2, 100 g·m−2, 200 g·m−2 and 400 g·m−2). The mean weight diameter (MWD), fractal dimension (D) and enrichment ratio (ER) are characteristic parameters of sediment particle size. The MWD and D were more sensitive to soil erosion and had a significant negative correlation with the slope angle and rainfall intensity. The performance of the MWD on the slope (5°) was less than the MWD on the slope (10°). The relationship between eroded sediment distribution characteristic parameters and the litter coverage mass had a significant influence on the content of coarse particles. The content of fine particles accelerated, decreased and then stabilized, whereas coarse particles increased first and then stabilized. The litter diameter and surface area were the main parameters that affected the MWD and D. Under different rain intensities and slopes, the ER varied inconsistently with litter coverage mass. Coarse particles were eroded easily and selectively, and soil erosion had no sorting effect on fine particles. These findings support the quantitative study of the relationship between the amount of litter coverage mass and the particle size of soil sediments.

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Long Term Observation of Atmospheric Aerosols at Sakai, Osaka, Japan

Journal of the Institute of Engineering ◽

10.3126/jie.v8i3.5933 ◽

1970 ◽

Vol 8 (3) ◽

pp. 72-74

Author(s):

Norio Ito ◽

Akira Mizohata

Keyword(s):

Atmospheric Aerosols ◽

Fine Particles ◽

Low Pressure ◽

Coarse Particles ◽

Nitrate Ions ◽

Long Term Observation ◽

Andersen Sampler

We have continuously observed the aerosols with 3 kinds of samplers; automatic daily sampler (DS), Andersen sampler (AS) and Low pressure Andersen Sampler (LPAS) at Sakai, Osaka, Japan. We started these sampling from 1986 (DS), 1993 (AS) and 2000 (LPAS). Yearly mean of fine particles (< 2.1μm) has decreased by about 10 μg/m3 from 1993 to 2009. By contrast the coarse particles (> 2.1μm) do not have explicit decrease. The main constituents in fine particles are carbon matters (EC and OC) and ions (sulphate and nitrate). Ions do not have decrease trend. These trends indicate that the decrease of fine particles might be caused by the decrease of carbon matters. DOI: http://dx.doi.org/10.3126/jie.v8i3.5933 JIE 2011; 8(3): 72-74

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Size-resolved exposure risk of persistent free radicals (PFRs) in atmospheric aerosols and their potential sources

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-14407-2020 ◽

2020 ◽

Vol 20 (22) ◽

pp. 14407-14417

Author(s):

Qingcai Chen ◽

Haoyao Sun ◽

Wenhuai Song ◽

Fang Cao ◽

Chongguo Tian ◽

...

Keyword(s):

Free Radicals ◽

Health Risks ◽

Atmospheric Aerosols ◽

Fine Particles ◽

Atmospheric Particulate Matter ◽

Particle Sizes ◽

Coarse Particles ◽

Upper Respiratory Tract ◽

Potential Health ◽

Combustion Sources

Abstract. Environmentally persistent free radicals (EPFRs) are a new type of substance with potential health risks. EPFRs are widely present in atmospheric particulates, but there is a limited understanding of the size-resolved health risks of these radicals. This study reports the exposure risks and source of EPFRs in atmospheric particulate matter (PM) of different particle sizes (<10 µm) in Linfen, a typical coal-burning city in China. The type of EPFRs in fine particles (< 2.1 µm) is different from that in coarse particles (2.1–10 µm) in both winter and summer. However, the EPFR concentration is higher in coarse particles than in fine particles in summer, and the opposite trend is found in winter. In both seasons, combustion sources are the main sources of EPFRs, with coal combustion as the major contributor in winter, while other fuels are the major source in summer. Dust contributes part of the EPFRs, and it is mainly present in coarse particles in winter and the opposite in summer. The upper respiratory tract was found to be the area with the highest risk of exposure to EPFRs of the studied aerosols, with an exposure equivalent to that of approximately 21 cigarettes per person per day. Alveolar exposure to EPFRs is equivalent to 8 cigarettes per person per day, with combustion sources contributing the most to EPFRs in the alveoli. This study helps us to better understand the potential health risks of atmospheric PM with different particle sizes.

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Impact of vehicular emissions on the formation of fine particles in the Sao Paulo Metropolitan Area: a numerical study with the WRF-Chem model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-14171-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 14171-14219 ◽

Cited By ~ 4

Author(s):

A. Vara-Vela ◽

M. F. Andrade ◽

P. Kumar ◽

R. Y. Ynoue ◽

A. G. Muñoz

Keyword(s):

Size Distribution ◽

Metropolitan Area ◽

Atmospheric Aerosols ◽

Fine Particles ◽

Sao Paulo ◽

Vehicular Emissions ◽

São Paulo ◽

Mass Size Distribution ◽

Mass Size ◽

The Impact

Abstract. The objective of this work is to evaluate the impact of vehicular emissions on the formation of fine particles (PM2.5; ≤ 2.5 μm in diameter) in the Sao Paulo Metropolitan Area (SPMA) in Brazil, where ethanol is used intensively as a fuel in road vehicles. Weather Research and Forecasting with Chemistry (WRF-Chem) model is used as photochemical modelling tool to describe the physico-chemical processes leading to evolution of number and mass size distribution of particles through gas-to-particle conversion. A vehicular emission model based on statistical information of vehicular activity is applied to simulate vehicular emissions over the studied area. The study period during a month, between 7 August and 6 September 2012, is considered to perform the numerical simulations due to the availability of experimental data from the NUANCE-SPS (Narrowing the Uncertainties on Aerosol and Climate Changes in Sao Paulo State) project that aims to characterize emissions of atmospheric aerosols in the SPMA. Results show that the emission of primary gases from vehicles led to a production between 20 and 30% due to new particles formation in relation to the total mass concentration of PM2.5 in the downtown SPMA. Dust and sea-salt aerosols contributed with 40–50% of the total PM10 (PM10; ≤ 10 μm in diameter) concentration. Furthermore, ground level O3 concentration decreased by about 2% when the aerosol-radiation feedback is taken into account. Over 40% of the formation of fine particles, by mass, was due to the emission of hydrocarbons, mainly aromatics. An increase in the number of small particles impaired the ultraviolet radiation and induced a decrease in ozone formation. Availability of experimental measurements of atmospheric aerosols and the application of the WRF-Chem model, which simulates feedbacks between meteorological variables and chemical species, made possible to represent some of the most important properties of fine particles in the SPMA such as the mass size distribution and chemical composition in addition to evaluate its formation potential through the gas-to-particle conversion processes.

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Observation of atmospheric aerosols at Mt. Hua and Mt. Tai in central and east China during spring 2009 – Part 2: Impact of dust storm on organic aerosol composition and size distribution

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-4065-2012 ◽

2012 ◽

Vol 12 (9) ◽

pp. 4065-4080 ◽

Cited By ~ 24

Author(s):

G. H. Wang ◽

J. J. Li ◽

C. L. Cheng ◽

B. H. Zhou ◽

M. J. Xie ◽

...

Keyword(s):

Size Distribution ◽

Dust Storm ◽

Fine Particles ◽

Organic Aerosols ◽

Gobi Desert ◽

Anthropogenic Aerosols ◽

Bimodal Size Distribution ◽

Coarse Mode ◽

Regional Sources ◽

Fine Mode

Abstract. PM10 and size-resolved particles (9-stage) were simultaneously collected at Mt. Hua and Mt. Tai in central and east China during the spring of 2009 including a massive dust storm occurring on 24 April (named as DS II), and determined for organic compounds to investigate the impact of dust storm on organic aerosols. High molecular weight (HMW) n-alkanes, fatty acids, and fatty alcohols and trehalose sharply increased and almost entirely stayed in coarse particles when dust storm was present, suggesting that high level of organic aerosols in the mountain atmospheres during the event largely originated from Gobi desert plants. However, most anthropogenic aerosols (e.g. PAHs, and aromatic and dicarboxylic acids) during the event significantly decreased due to a dilution effect, indicating that anthropogenic aerosols in the mountain atmospheres during the nonevent period largely originated from local/regional sources rather than from long-range transport. Trehalose, a metabolism product enriched in biota in dry conditions, was 62 ± 78 and 421 ± 181 ng m−3 at Mt. Hua and Mt. Tai during DS II, 10–30 times higher than that in the nonevent time, indicating that trehalose may be a tracer for dust emissions from Gobi desert regions. Molecular compositions of organic aerosols in the mountain samples demonstrate that domestic coal burning is still the major source of PAHs in China. n-Alkanes and fatty acids showed a bimodal size distribution during the nonevent with a major peak in fine mode (<2.1 μm) and a small peak in coarse mode (>2.1 μm). The coarse mode significantly increased and even dominated over the whole size range when dust was present. Glucose and trehalose were also dominant in the coarse mode especially in the DS II time. PAHs and levoglucosan concentrated in fine particles with no significant changes in size distribution when dust storm occurred. However, phthalic and succinic acids showed bimodal size distribution pattern with an increase in coarse mode during the event, because both are formed via a gas phase oxidation and a subsequent condensation/adsorption onto aerosol phase. In contrast, terephthalic and malic acids are mostly emitted from combustion process as fine particles, thus both showed a fine mode pattern during the whole campaign with a minor peak in coarse mode caused by an increased coagulation with dust during the event. Geometric mean diameters (GMDs) of the organic aerosols above are in general larger at Mt.~Hua than at Mt. Tai during the nonevent period. We found that during the event GMD of the fine mode organics that derived mostly from the local/regional sources rather than Gobi desert became smaller while GMD of them in coarse mode became larger. Such a splitting in sizes during the event is most likely caused by decreased fine particle coagulation due to dilution and increased adsorption/coagulation with dust.

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Observation of atmospheric aerosols at Mt. Hua and Mt. Tai in Central and East China during spring 2009 – Part 2: Impact of dust storm on organic aerosol composition and size distribution

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-33543-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 33543-33582

Author(s):

G. H. Wang ◽

J. J. Li ◽

C. L. Cheng ◽

B. H. Zhou ◽

M. J. Xie ◽

...

Keyword(s):

Size Distribution ◽

Dust Storm ◽

Fine Particles ◽

Organic Aerosols ◽

Gobi Desert ◽

Anthropogenic Aerosols ◽

Bimodal Size Distribution ◽

Coarse Mode ◽

Regional Sources ◽

Fine Mode

Abstract. PM10 and size-resolved particles (9-stage) were simultaneously collected at Mt. Hua and Mt. Tai in Central and East China during the spring of 2009 including a massive dust storm occurring on April 24th (named as DS II), and determined for organic compounds to investigate the impact of dust storm on organic aerosols. High molecular weight (HMW) n-alkanes, fatty acids, and fatty alcohols and trehalose sharply increased and almost entirely stayed in coarse particles when dust storm was present, suggesting that high level of organic aerosols in the mountain atmospheres during the event originated from biogenic sources in the Gobi desert. However, most anthropogenic aerosols (e.g., PAHs, aromatic acids and dicarboyxlic acids) during the event significantly decreased due to a dilution effect, indicating that anthropogenic aerosols in the mountain air during the nonevent period are largely derived from local/regional sources rather than from long-range transport. Our results indicate that trehalose can be taken as a new tracer for dust emissions from desert regions since trehalose was negligible in the nonevent but abundant in the event. Molecular compositions of organic aerosols in the mountain samples further demonstrate that domestic coal burning is still the major source of PAHs in China. n-Alkanes and fatty acids showed a bimodal size distribution during the nonevent with a major peak in fine mode (<2.1 μm) and a small peak in coarse mode (>2.1 μm). The coarse mode significantly increased and even dominated over the whole size range when dust was present. Glucose and trehalose were also dominant in the coarse mode especially in the DS II time. PAHs and levoglucosan concentrated in fine particles with no significant changes in size distribution when dust storm occurred. However, phthalic and succinic acids showed bimodal size distribution pattern with an increase in coarse mode during the event, because both are formed via a gas phase oxidation and a subsequent condensation/adsorption onto aerosol phase. In contrast, terephthalic and malic acids are mostly emitted from combustion process as fine particles, thus both showed a fine mode pattern during the whole campaign with a minor peak in coarse mode caused by an increased coagulation with dust during the event. Geometric mean diameters (GMDs) of the organic aerosols above are in general larger at Mt. Hua than at Mt. Tai during the nonevent period. We found that during the event GMD of the fine mode organics that derived mostly from the local/regional sources rather than Gobi desert became smaller while GMD of them in coarse mode became larger. Such a polarization in sizes during the event is most likely caused by decreased fine particle coagulation due to dilution and increased adsorption/coagulation with dust.

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