scholarly journals 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

2012 ◽  
Vol 12 (9) ◽  
pp. 4065-4080 ◽  
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.

scholarly journals 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

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.

Regional and Transported A erosols in Ambient A tmosphere of Raipur,India, during W inter

2021 ◽  
Vol 30 (1) ◽  
pp. 7-17
Author(s):  
Manas Kanti Deb ◽  
Mithlesh Mahilang ◽  
Jayant Nirmalkar
Keyword(s):  
Size Distribution ◽  
Long Range ◽  
Fine Particles ◽  
Characteristic Size ◽  
Long Range Transport ◽  
Bimodal Size Distribution ◽  
Entire Study ◽  
Coarse Mode ◽  
Range Transport ◽  
Air Trajectory

Size fractionated atmospheric aerosols were collected using cascade impactor sampler on quartz flter substrate during October 2015 to February 2016 in campus of Pt Ravishankar Shukla University of Raipur Chhattisgarh. The size of aerosol particles is of crucial importance to several processes in the atmosphere. The relative concentrations in both modes are responsible for the variability observed in the shape of the size distribution. Characteristic size distributions of measured aerosol over central India showed identifcation of three main behaviour types during entire study period: (i) month in which bimodal size distribution dominated in coarse mode (October 2015, 5 December 2015 and January, 2016), (ii) those months in which bimodal distribution equally intense in both one, and coarse modes (November, 2015) and (iii) those which were mainly dominated within fine (February, 2016, December, 2015). The two-subsequent month namely November 2015 and December 2015 shows bimodal size distribution with dominance in fine size range in comparison to coarse mode, possibly these high loading of one particles is due to long range transport. The peculiar observation of air trajectory shows that there is increase in fine particles concentration during December 2015, although there in increase in temperature and wind speed. The reason for this high concentration is long range transport of air masses. However, January has normal trend in particular matter concentration. The important finding of the present study based on characteristic size distribution and air trajectory plots accomplishes that fine particles are obtained through long range transport whereas coarse particles are mainly from local origin.

scholarly journals Evolution of aerosol chemistry in Xi'an, inland China during the dust storm period of 2013 – Part 1: Sources, chemical forms and formation mechanisms of nitrate and sulfate

2014 ◽  
Vol 14 (11) ◽  
pp. 17439-17478
Author(s):  
G. H. Wang ◽  
Y. Huang ◽  
J. Tao ◽  
Y. Q. Ren ◽  
F. Wu ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Dust Storm ◽  
Water Soluble ◽  
Current Work ◽  
Ageing Process ◽  
Gobi Desert ◽  
Chemical Compositions ◽  
Aerosol Chemistry ◽  
Coarse Mode ◽  
Fine Mode

Abstract. In the current work TSP sample was hourly collected in Xi'an, an inland mega-city of China near the Loess Plateau, during a dust storm event of 2013 (9 March 18:00–12 March 10:00 LT), along with a size-resolved aerosol sampling and an online measurement of PM2.5. The TSP and size-resolved samples were determined for EC, OC, water-soluble organic carbon (WSOC) and nitrogen (WSON), inorganic ions and elements to investigate aerosol chemistry evolution. Hourly concentrations of Cl−, NO3−, SO42−, Na+ and Ca2+ in the TSP samples reached up to 34, 12, 180, 72 and 28 μg m−3, respectively, when dust peak arrived over Xi'an. Chemical compositions of the TSP samples showed that NH4+ and NO3− strongly correlated each other in the whole observation period (r2=0.76), while SO42− and Cl− well correlated with Na+, Ca2+, Mg2+ and K+ (r2>0.85). Size distributions of NH4+ and NO3− presented a same pattern, which dominated in the coarse mode (>2.1 μm during the event and predominated in the fine mode (<2.1 μm) during the non-event. SO42− and Cl− also dominated in the coarse mode during the event, but both exhibited two equivalent peaks in the fine and coarse modes during the non-event, respectively, due to the fine mode accumulations of secondarily produced SO42− and biomass burning emitted Cl− and the coarse mode enrichments of urban soil-derived SO42− and Cl−. Linear fit regression analysis further indicated that SO42− and Cl− in the dust samples possibly exist as Na2SO4, CaSO4 and NaCl, which directly originated from Gobi desert surface soil, while NH4+ and NO3− in the dust samples exist as NH4NO3. We propose a mechanism to explain these observations in which aqueous phase of dust particle surface is formed via uptake of water vapor by hygroscopic Na2SO4, CaSO4 and NaCl, followed by heterogeneous formation of nitrate on the liquid phase and subsequent absorption of ammonia. Our data indicate that 54 ± 20% and 60 ± 23% of NH4+ and NO3− during the dust period were secondarily produced via this pathway with the remaining derived from Gobi desert and Loess Plateau while SO42− in the event almost entirely originated from the source regions. To the best of our knowledge, the current work for the first time revealed an infant state of dust ageing process in the regions near the source, which is helpful for researchers to understand the panorama of dust ageing process from the source area to the downwind region.

scholarly journals Evolution of aerosol chemistry in Xi'an, inland China, during the dust storm period of 2013 – Part 1: Sources, chemical forms and formation mechanisms of nitrate and sulfate

2014 ◽  
Vol 14 (21) ◽  
pp. 11571-11585 ◽  
Author(s):  
G. H. Wang ◽  
C. L. Cheng ◽  
Y. Huang ◽  
J. Tao ◽  
Y. Q. Ren ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Loess Plateau ◽  
Dust Storm ◽  
East Asian ◽  
Asian Dust ◽  
Water Soluble ◽  
Ageing Process ◽  
Gobi Desert ◽  
Coarse Mode ◽  
Fine Mode

Abstract. A total suspended particulate (TSP) sample was collected hourly in Xi'an, an inland megacity of China near the Loess Plateau, during a dust storm event of 2013 (9 March 18:00−12 March 10:00 LT), along with a size-resolved aerosol sampling and an online measurement of PM2.5. The TSP and size-resolved samples were determined for elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC) and nitrogen (WSON), inorganic ions and elements to investigate chemistry evolution of dust particles. Hourly concentrations of Cl−, NO3−, SO42−, Na+ and Ca2+ in the TSP samples reached up to 34, 12, 180, 72 and 28 μg m−3, respectively, when dust peak arrived over Xi'an. Chemical compositions of the TSP samples showed that during the whole observation period NH4+ and NO3− were linearly correlated with each other (r2=0.76) with a molar ratio of 1 : 1, while SO42− and Cl− were well correlated with Na+, Ca2+, Mg2+ and K+ (r2 > 0.85). Size distributions of NH4+ and NO3− presented a same pattern, which dominated in the coarse mode (> 2.1 μm) during the event and predominated in the fine mode (< 2.1 μm) during the non-event. SO42− and Cl− also dominated in the coarse mode during the event hours, but both exhibited two equivalent peaks in both the fine and the coarse modes during the non-event, due to the fine-mode accumulations of secondarily produced SO42− and biomass-burning-emitted Cl- and the coarse-mode enrichments of urban soil-derived SO42− and Cl−. Linear fit regression analysis further indicated that SO42− and Cl− in the dust samples possibly exist as Na2SO4, CaSO4 and NaCl, which directly originated from Gobi desert surface soil, while NH4+ and NO3− in the dust samples exist as NH4NO3. We propose a mechanism to explain these observations in which aqueous phase of dust particle surface is formed via uptake of water vapor by hygroscopic salts such as Na2SO4 and NaCl, followed by heterogeneous formation of nitrate on the liquid phase and subsequent absorption of ammonia. Our data indicate that 54 ± 20% and 60 ± 23% of NH4+ and NO3− during the dust period were secondarily produced via this pathway, with the remaining derived from the Gobi desert and Loess Plateau, while SO42− in the event almost entirely originated from the desert regions. Such cases are different from those in the East Asian continental outflow region, where during Asia dust storm events SO42− is secondarily produced and concentrates in sub-micrometer particles as (NH4)2SO4 and/or NH4HSO4. To the best of our knowledge, the current work for the first time revealed an infant state of the East Asian dust ageing process in the regions near the source, which is helpful for researchers to understand the panorama of East Asian dust ageing process from the desert area to the downwind region.

scholarly journals Impacts of the Variations of Aerosols Components and Relative Humidity on the Visibility and Particles Size Distribution of the Desert Atmosphere

2021 ◽  
pp. 42-65
Author(s):  
S. U. Yerima ◽  
U. Y. Abdulkarim ◽  
B. I. Tijjani ◽  
U. M. Gana ◽  
M. Idris ◽  
...  
Keyword(s):  
Size Distribution ◽  
Hygroscopic Growth ◽  
Angstrom Exponent ◽  
Microphysical Properties ◽  
Coarse Mode ◽  
Ångström Exponent ◽  
Particles Size Distribution ◽  
Fine Mode ◽  
The Mean ◽  
Ångstrom Exponent

This paper investigates the Impact of relative humidity, varying the concentrations of water-soluble aerosol particle concentrations (WASO), Mineral Nuclei Mode Aerosols Particle Concentration (MINN), mineral accumulation mode, nonspherical (MIAN) aerosol particles concentrations and Mineral Coarse Mode Aerosols Particle Concentration (MICN) on the visibility and particles size distribution of desert aerosols based on microphysical properties of desert aerosols. The microphysical properties (the extinction coefficients, volume mix ratios, dry mode radii and wet mode radii) were extracted from Optical Properties of Aerosols and Clouds (OPAC 4.0) at eight relative humidities, RHs (00 to 99%) and at the spectral visible range of 0.4-0.8mm, the concentrations were varied to obtain five different models for each above-mentioned component. Regression analysis of some standard equations were used to determine the Angstrom exponent (α), the turbidity coefficient (β), the curvature (α2), humidification factor (), the mean exponent of aerosol growth curve (µ) and the mean exponent of aerosol size distributions (n). The values of angstrom exponent (α) were observed to be less than 1 throughout the five models at all RHs for the four studied components, and this signifies the dominance of coarse mode particles over fine mode particles. But the magnitude of the angstrom exponent (α) fluctuates all through the studied components except for WASO which increased with the increase in RH across the models and this also signifies the dominance of coarse mode particles with some traces of fine mode particles. The investigation also revealed that the curvature (α2) has both monomodal (negative signs) and bimodal (positive signs) types of distributions all through the five models and this also signifies the dominance of coarse mode particles with some traces of fine mode particles across the individual models for all the studied components. it was also found that the visibility decreased with the increase in RH and increased with the increase in wavelength. The investigation further revealed that the turbidity coefficient (β) fluctuates with the increase in RH and the particles concentrations, and this might be due to major coagulation and sedimentation. The analysis further found that there is a direct inverse power relation between the humidification factor and the mean exponent of aerosols size distribution with the mean exponent of aerosols growth curve. It was also found that as the magnitude of µ increased for MIAN, MINN and MICN, the effective hygroscopic growth  decreased. For WASO, it was found that as the magnitude of µ decreased, the effective hygroscopic growth  increased with the increase in particles concentrations and RH. The decreased in the magnitude of µ for WASO might be due to the fact that as we increase the non-hygroscopic particles, we decrease the deliquescence. The mean exponent of aerosol size distribution (n) being less than 3 shows foggy condition of the desert atmosphere the four investigated components and five studied models.

scholarly journals Size distributions of polycyclic aromatic hydrocarbons in urban atmosphere: sorption mechanism and source contributions to respiratory deposition

2015 ◽  
Vol 15 (15) ◽  
pp. 20811-20850 ◽  
Author(s):  
Y. Lv ◽  
X. Li ◽  
T. T. Xu ◽  
T. T. Cheng ◽  
X. Yang ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Cancer Risk ◽  
Size Distribution ◽  
Health Effects ◽  
Aromatic Hydrocarbons ◽  
Fine Particles ◽  
Deposition Fluxes ◽  
Adverse Health Effects ◽  
Polycyclic Aromatic ◽  
Fine Mode

Abstract. Current knowledge on atmospheric particle-phase polycyclic aromatic hydrocarbons (PAHs) size distribution remains incomplete. Information is missing on sorption mechanisms and the influence of the PAHs' sources on their transport in human respiratory system. Here we present the studies systematically investigating the modal distribution characteristics of the size-fractioned PAHs and calculating the source contribution to adverse health effects through inhalation. Aerosol samples with nine size fractions were collected from Shanghai urban air over one year period 2012–2013. A high correlation coefficient existed between measured and predicted values (R2= 0.87), indicated that the data worked very well in current study. Most PAHs were observed on the small particles followed with seasonality differences. When normalized by PAHs across particle diameters, the size distribution of PAHs exhibited bimodal patterns, with a peak (0.4–2.1 μm) in fine mode and another peak (3.3–9.0 μm) in coarse mode, respectively. Along with the increasing ring number of PAHs, the intensity of the fine mode peak increased, while coarse mode peak decreased. Plotting of log(PAH/PM) against log(Dp) showed that all slope values were above −1 with the increase towards less-ring PAHs, suggesting that multiple mechanisms, i.e. adsorption and absorption controlled the PAHs on particles, but adsorption played a much stronger role for 5- and 6-ring than 3- and 4-ring PAHs. The mode distribution behavior of PAHs showed that fine particles were major carriers for the more-ring PAHs. Further calculations using inhaling PAHs data showed the total deposition fluxes in respiratory tract were 8.8 ± 2.0 ng h-1. Specifically, fine particles contributed 10–40 % of PAHs deposition fluxes to the alveolar region, while coarse particles contributed 80–95 % of ones to the head region. Estimated lifetime cancer risk (LCR) for people exercised in haze days (1.5 × 10-6) was bigger than the cancer risk guideline value (10-6). The largest PAHs contribution for LCR mainly came from the accumulation particles. Based on source apportionment results generated by positive matrix factorization (PMF), it was found that the cancer risk caused in accumulated mode mainly resulted from biomass burning (24 %), coal combustion (25 %) and vehicular emission (27 %). The present results contribute to a mechanistic understanding of PAHs size distribution causing adverse health effects and will help develop some source control strategies or policies by relying on respiratory assessment data.

scholarly journals Investigating the quality of modeled aerosol profiles based on combined lidar and sunphotometer data

2017 ◽  
Author(s):  
Nikolaos Siomos ◽  
Dimitrios S. Balis ◽  
Anastasia Poupkou ◽  
Natalia Liora ◽  
Spyridon Dimopoulos ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Mass Concentration ◽  
Fine Particles ◽  
Center Of Mass ◽  
Concentration Profiles ◽  
Free Troposphere ◽  
Desert Dust ◽  
Coarse Mode ◽  
Dust Component ◽  
Fine Mode

Abstract. In this study we present an evaluation of the Comprehensive Air quality Model with extensions CAMx for Thessaloniki using radiometric and lidar data. The aerosol mass concentration profiles of CAMx are compared against the fine and coarse mode aerosol concentration profiles retrieved by the Lidar-Radiometer Inversion Code LIRIC. The CAMx model and the LIRIC algorithm results were compared in terms of mean mass concentration profiles, center of mass and integrated mass concentration in the boundary layer and the free troposphere The mean mass concentration comparison resulted in profiles within the same order of magnitude and similar vertical structure for the fine particles. The mean center of mass values are also close with a fractional bias of 24.8 %. On the opposite side, the coarse mode appears to be underestimated by the model below 4 km and overestimated above. In order to grasp the reasons behind the discrepancies, we investigate the effect of aerosol components that are not properly included in the model's emission inventory and boundary conditions such as the wildfires and the desert dust component. The identification of the cases that are affected by wildfires is performed using wind backward trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory Model HYSPLIT in conjunction with satellite fire pixel data from the MODIS Terra and Aqua Global Monthly Fire Location Product MCD14ML. By removing those cases the correlation coefficient improves from 0.44 to 0.86 for the fine mode integrated mass in the boundary layer. The fine mode center of mass fractional bias also decreases to 16.9 %. Concerning the analysis on the desert dust component, the simulations from the updated version of the former Dust Regional Atmospheric Model called BSC-DREAM8b were deployed. When only the desert dust cases are taken into account, BSC-DREAM8b generally outperforms CAMx when compared with LIRIC, achieving a correlation of 0.91 and a fractional bias of −18.9 % for the integrated mass in the free troposphere and a correlation of 0.44 for the center of mass. CAMx, on the other hand, both underestimates and anti-correlates the integrated mass in the free troposphere. Consequently, the accuracy of CAMx is limited concerning the transported dust cases. We conclude that the performance of CAMx appears to be best for the fine particles, especially in the boundary layer. At the same time it systematically fails to successfully predict the coarse mode. Sources of particles not properly taken into account by the model are confirmed to negatively affect its performance.

scholarly journals Observation of atmospheric aerosols at Mt. Hua and Mt. Tai in central and east China during spring 2009 – Part 1: EC, OC and inorganic ions

2011 ◽  
Vol 11 (9) ◽  
pp. 4221-4235 ◽  
Author(s):  
G. Wang ◽  
J. Li ◽  
C. Cheng ◽  
S. Hu ◽  
M. Xie ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Dust Storm ◽  
Fine Particles ◽  
Ph Value ◽  
Inorganic Ions ◽  
East China ◽  
Storm Event ◽  
Ph Values ◽  
Coarse Mode ◽  
Dust Storm Event

Abstract. PM10 and size-segregated samples were simultaneously collected at Mt. Hua (2060 m a.s.l.) and Mt. Tai (1545 m a.s.l.) in central and east coastal China during spring, 2009 including an intensive dust storm event occurring on 24 April, and determined for EC, OC and inorganic ions. During the non-dust storm period particles, EC, OC and ions except for SO42− were 2–10 times more abundant at Mt. Tai than at Mt. Hua. SO42− (13 ± 7.1 μg m−3) at Mt. Hua was the dominant ion, followed by NO3− (5.0 ± 3.9 μg m−3), NH4+ (2.5 ± 1.3 μg m−3) and Ca2+ (1.6 ± 0.8 μg m−3). In contrast, at Mt. Tai NO3− was most abundant (20 ± 14 μg m−3), followed by SO42− (16 ± 13 μg m−3), NH4+ (12 ± 8.9 μg m−3) and Ca2+ (3.9 ± 2.1 μg m−3). The fact of NO3− exceeding over SO42− at Mt. Tai may suggest the changes in chemical composition of the atmosphere over east China due to sharply increasing vehicle emission. pH values of the water-extracts of PM10 samples indicate that at the two mountain sites aerosols transported from the south regions are more acidic than those from the north and more acidic at Mt. Tai than at Mt. Hua during the non-dust storm period. During the dust storm event particle mass, OC, Na+, K+, Mg2+ and Ca2+ at both sites increased by a factor of 1–9, while EC, NO3− and NH4+ decreased by 20–80 %. However, SO42− concentrations (13 ± 7.7 μg m−3 at Mt. Hua and 15 ± 5.6 μg m−3 at Mt. Tai, respectively) at the two sites during the episode were comparable and did not change significantly compared to those in the non-dust storm period, probably due to a similar level of free tropospheric SO2 in central and east China. Compared with those at Mt. Hua the coarse modes (>2.1 μm) of K+ and SO42− at Mt. Tai during the non-event period were more abundant and the coarse mode of NO3− was less abundant. When the dust storm was present all ions significantly moved toward coarse particles, except for NH4+, with a disappeared peak in fine mode (<2.1 μm) for NO3−. Linear regression for ion equivalents in fine particles indicates that ammonium exists in the forms of NH4NO3 and NH4HSO4 at Mt. Hua and NH4NO3 and (NH4)2SO4 at Mt. Tai during both the nonevent and the event periods. While the regression for coarse mode of Ca2+ suggests a close coupling of dust with nitrate during the nonevent time and with sulfate during the dust-storm period. pH values of the size-resolved samples further suggest that during the nonevent period most acidic particles at Mt. Hua are in the range of 0.7–1.1 μm, while those at Mt. Tai are in the range of 1.1–2.1 μm. Aerosols at both sites became alkaline during the event, but the Mt. Tai particles still showed a lower pH value.

scholarly journals 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

2012 ◽  
Vol 12 (8) ◽  
pp. 21355-21397 ◽  
Author(s):  
G. H. Wang ◽  
B. H. Zhou ◽  
C. L. Cheng ◽  
J. J. Cao ◽  
J. J. Meng ◽  
...  
Keyword(s):  
Size Distribution ◽  
Fine Particles ◽  
Major Ions ◽  
Ground Surface ◽  
Sampling Period ◽  
Water Soluble ◽  
Gobi Desert ◽  
Urban Air ◽  
Coarse Particles ◽  
Aerosol Chemistry

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.

scholarly journals Observation of biogenic secondary organic aerosols in the atmosphere of a mountain site in central China: temperature and relative humidity effects

2013 ◽  
Vol 13 (7) ◽  
pp. 17643-17674 ◽  
Author(s):  
J. J. Li ◽  
G. H. Wang ◽  
J. J. Cao ◽  
X. M. Wang ◽  
R. J. Zhang
Keyword(s):  
Relative Humidity ◽  
Fine Particles ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Sampling Period ◽  
Oxidation Products ◽  
Central China ◽  
Clear Trend ◽  
Aerosol Acidity ◽  
Fine Mode

Abstract. Secondary organic aerosols (SOA) derived from isoprene, pinene and caryophyllene were determined for PM10 and size-segregated (9-stage) aerosols collected at the summit (2060 m, a.s.l.) of Mt. Hua, central China during the summer of 2009. Concentrations of estimated isoprene, α-/β-pinene and β-caryophyllene derived SOC are 81± 53, 29 ± 14 and 98 ± 53 ng m−3, accounting for 2.7± 1.0%, 0.8 ± 0.2% and 2.1 ± 1.0% of OC, respectively. Concentrations of biogenic (BSOA, the isoprene/pinene/caryophyllene oxidation products) and anthropogenic (ASOA, mainly aromatic acids) SOA positively correlated with temperature (R=0.57–0.90). However, a decreasing trend of BSOA concentration with an increase in relative humidity (RH) was observed during the sampling period, although a clear trend between ASOA and RH was not found. Based on the AIM Model calculation, we found that during the sampling period an increase in RH resulted in a decrease in the aerosol acidity and thus reduced the effect of acid-catalysis on BSOA formation. Size distribution measurement showed that most of the determined isoprene derived SOA may form in aerosol phase and enriched in the fine mode (<2.1μm). 3-Hydroxyglutaric acid, 3-methyl-1,2,3-butanetricarboxylic acid and β-caryophyllinic acid are only presented in fine particles. However, cis-pinonic acid presents a large peak in the coarse mode (>2.1 μm) due to its highly volatile nature.

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