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 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 East Asian dust storm in May 2017: observations, modelling, and its influence on the Asia-Pacific region

2018 ◽  
Vol 18 (11) ◽  
pp. 8353-8371 ◽  
Author(s):  
Xiao-Xiao Zhang ◽  
Brenton Sharratt ◽  
Lian-You Liu ◽  
Zi-Fa Wang ◽  
Xiao-Le Pan ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Dust Storm ◽  
North Pacific ◽  
East Asian ◽  
Asian Dust ◽  
Asia Pacific ◽  
Gobi Desert ◽  
Dust Event ◽  
The North ◽  
The North Pacific

Abstract. A severe dust storm event originated from the Gobi Desert in Central and East Asia during 2–7 May 2017. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products, hourly environmental monitoring measurements from Chinese cities and East Asian meteorological observation stations, and numerical simulations, we analysed the spatial and temporal characteristics of this dust event as well as its associated impact on the Asia-Pacific region. The maximum observed hourly PM10 (particulate matter with an aerodynamic diameter ≤ 10 µm) concentration was above 1000 µg m−3 in Beijing, Tianjin, Shijiazhuang, Baoding, and Langfang and above 2000 µg m−3 in Erdos, Hohhot, Baotou, and Alxa in northern China. This dust event affected over 8.35 million km2, or 87 % of the Chinese mainland, and significantly deteriorated air quality in 316 cities of the 367 cities examined across China. The maximum surface wind speed during the dust storm was 23–24 m s−1 in the Mongolian Gobi Desert and 20–22 m s−1 in central Inner Mongolia, indicating the potential source regions of this dust event. Lidar-derived vertical dust profiles in Beijing, Seoul, and Tokyo indicated dust aerosols were uplifted to an altitude of 1.5–3.5 km, whereas simulations by the Weather Research and Forecasting with Chemistry (WRF-Chem) model indicated 20.4 and 5.3 Tg of aeolian dust being deposited respectively across continental Asia and the North Pacific Ocean. According to forward trajectory analysis by the FLEXible PARTicle dispersion (FLEXPART) model, the East Asian dust plume moved across the North Pacific within a week. Dust concentrations decreased from the East Asian continent across the Pacific Ocean from a magnitude of 103 to 10−5 µg m−3, while dust deposition intensity ranged from 104 to 10−1 mg m−2. This dust event was unusual due to its impact on continental China, the Korean Peninsula, Japan, and the North Pacific Ocean. Asian dust storms such as those observed in early May 2017 may lead to wider climate forcing on a global scale.

scholarly journals East Asian dust storm in May 2017: observations, modelling and its influence on Asia-Pacific region

2018 ◽  
Author(s):  
Xiao-Xiao Zhang ◽  
Brenton Sharratt ◽  
Lian-You Liu ◽  
Zi-Fa Wang ◽  
Xiao-Le Pan ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Dust Storm ◽  
North Pacific ◽  
North Pacific Ocean ◽  
East Asian ◽  
Asian Dust ◽  
Asia Pacific ◽  
Gobi Desert ◽  
Dust Event ◽  
The North

Abstract. A severe dust storm event originated from the Gobi Desert in Central and East Asia during 2–7 May, 2017. Based on moderate resolution imaging spectroradiometer (MODIS) satellite products, hourly environmental monitoring measurements from 367 Chinese cities and more than 2000 East Asian meteorological observation stations, and numerical simulations, we analysed the spatial and temporal characteristics of this dust event as well as its associated impact on the Asia-Pacific region. The maximum observed hourly PM10 (particulate matter with an aerodynamic diameter &amp;leq; 10 μm) concentration was above 1000 μg m−3 in Beijing, Tianjin, Shijiazhuang, Baoding, and Langfang and above 2000 μg m−3 in Erdos, Hohhot, Baotou, and Alxa in northern China. This dust event affected over 8.35 million km2, or 87 % of mainland China, and significantly deteriorated air quality in 316 cities of the 367 cities examined across China. The maximum surface wind speed during the dust storm was 23–24 m s−1 in the Mongolian Gobi Desert and 20–22 m s−1 in central Inner Mongolia, indicating the potential source regions of this dust event. Lidar-derived vertical dust profiles in Beijing, Seoul, and Tokyo indicated dust aerosols were uplifted to an altitude of 1.5–3.5 km whereas simulations by the Weather Research and Forecasting with Chemistry (WRF-Chem) model indicated 20.4 Tg and 5.3 Tg of aeolian dust being deposited respectively across continental Asia and the North Pacific Ocean. According to forward trajectory analysis by the FLEXible PARTicle dispersion (FLEXPART) model, the East Asian dust plume moved across the North Pacific within a week. Dust concentrations decreased from East Asian continent across the Pacific Ocean from a magnitude of 103 to 10−5 μg m−3, while dust deposition intensity ranged from 104 to 10−1 mg m−2. This dust event was unusual due to its impact on continental China, Korea, Japan and North Pacific Ocean. Asian dust storms such as observed in early May 2017 may lead to wider climate forcing on a global scale.

scholarly journals Dicarboxylic acids, oxoacids, benzoic acid, <i>α</i>-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

2016 ◽  
Vol 16 (8) ◽  
pp. 5263-5282 ◽  
Author(s):  
Dhananjay K. Deshmukh ◽  
Kimitaka Kawamura ◽  
Manuel Lazaar ◽  
Bhagawati Kunwar ◽  
Suresh K. R. Boreddy
Keyword(s):  
Organic Carbon ◽  
Benzoic Acid ◽  
Biomass Burning ◽  
Unsaturated Fatty Acids ◽  
Glyoxylic Acid ◽  
Water Soluble ◽  
Size Distributions ◽  
Strong Correlations ◽  
Coarse Mode ◽  
Fine Mode

Abstract. Size-segregated aerosols (nine stages from < 0.43 to > 11.3 µm in diameter) were collected at Cape Hedo, Okinawa, in spring 2008 and analyzed for water-soluble diacids (C2–C12), ω-oxoacids (ωC2–ωC9), pyruvic acid, benzoic acid, and α-dicarbonyls (C2–C3) as well as water-soluble organic carbon (WSOC), organic carbon (OC), and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and MSA−). In all the size-segregated aerosols, oxalic acid (C2) was found to be the most abundant species, followed by malonic and succinic acids, whereas glyoxylic acid (ωC2) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C2–C5), ωC2, and Gly as well as WSOC and OC peaked at fine mode (0.65–1.1 µm) whereas azelaic (C9) and 9-oxononanoic (ωC9) acids peaked at coarse mode (3.3–4.7 µm). Sulfate and ammonium were enriched in fine mode, whereas sodium and chloride were in coarse mode. Strong correlations of C2–C5 diacids, ωC2 and Gly with sulfate were observed in fine mode (r =  0.86–0.99), indicating a commonality in their secondary formation. Their significant correlations with liquid water content in fine mode (r =  0.82–0.95) further suggest an importance of the aqueous-phase production in Okinawa aerosols. They may also have been directly emitted from biomass burning in fine mode as supported by strong correlations with potassium (r =  0.85–0.96), which is a tracer of biomass burning. Bimodal size distributions of longer-chain diacid (C9) and oxoacid (ωC9) with a major peak in the coarse mode suggest that they were emitted from the sea surface microlayers and/or produced by heterogeneous oxidation of biogenic unsaturated fatty acids on sea salt particles.

scholarly journals Investigation of aged aerosols in size-resolved Asian dust storm particles transported from Beijing, China to Incheon, Korea using low-<i>Z</i> particle EPMA

2013 ◽  
Vol 13 (10) ◽  
pp. 27971-28016 ◽  
Author(s):  
H. Geng ◽  
H. J. Hwang ◽  
X. Liu ◽  
S. Dong ◽  
C.-U. Ro
Keyword(s):  
Organic Carbon ◽  
Dust Storm ◽  
Aging Process ◽  
Mineral Dust ◽  
Asian Dust ◽  
Sea Salt ◽  
Water Soluble ◽  
The Yellow Sea ◽  
Asian Dust Storm ◽  
Beijing China

Abstract. This is the first study of Asian dust storm (ADS) particles collected in Beijing, China and Incheon, Korea during the same spring ADS event. Using a seven-stage May impactor and a quantitative electron probe X-ray microanalysis (ED-EPMA, also known as low-Z particle EPMA), we examined the composition and morphology of 4200 aerosol particles at stages 1–6 (with a size cut-off of 16, 8, 4, 2, 1, and 0.5 μm in equivalent aerodynamic diameter, respectively) collected during an ADS event on 28–29 April 2005. The results showed that there were large differences in the chemical compositions between particles in sample S1 collected in Beijing immediately after the peak time of the ADS and in samples S2 and S3, which were collected in Incheon approximately 5 h and 24 h later, respectively. In sample S1, mineral dust particles accounted for more than 88% in relative number abundance at stages 1–5, and organic carbon (OC) and reacted NaCl-containing particles accounted for 24% and 32%, respectively, at stage 6. On the other hand, in samples S2 and S3, in addition to approximately 60% mineral dust, many sea salt particles reacted with airborne SO2 and NOx, often mixed with mineral dust, were encountered at stages 1–5, and (C, N, O, S)-rich particles (likely a mixture of water-soluble organic carbon with (NH4)2SO4 and NH4NO3) and K-containing particles were abundantly observed at stage 6. This suggests that the secondary aerosols and the internal mixture of mineral dust with sea spray aerosol increased when the ADS particles passed over the Yellow Sea. In the reacted or aged mineral dust and sea salt particles, nitrate-containing and both nitrate- and sulfate-containing species vastly outnumbered the sulfate-containing species, implying that ambient nitrogen oxides had a greater influence on the atmospheric particles during the ADS episode than SO2. In addition to partially- or totally-reacted CaCO3, reacted or aged Mg-containing aluminosilicates (likely including amesite, allophite, vermiculite, illite, and montmorillonite) were observed frequently in samples S2 and S3; and furthermore, both the atomic concentration ratios of [Mg]/[Al] and [Mg]/[Si] were elevated compared to that in sample S1. This shows that a great evolution or aging process must have occurred on the mineral dust. This indicates that the number abundance, reactivity with gaseous pollutants, and ratios of [Mg]/[Al] and [Mg]/[Si] of Mg-containing aluminosilicates are promising indices of the aging process of ADS particles during long-range transport.

scholarly journals Investigation of aged aerosols in size-resolved Asian dust storm particles transported from Beijing, China, to Incheon, Korea, using low-<i>Z</i> particle EPMA

2014 ◽  
Vol 14 (7) ◽  
pp. 3307-3323 ◽  
Author(s):  
H. Geng ◽  
H. Hwang ◽  
X. Liu ◽  
S. Dong ◽  
C.-U. Ro
Keyword(s):  
Organic Carbon ◽  
Dust Storm ◽  
Mineral Dust ◽  
Asian Dust ◽  
Water Soluble ◽  
The Yellow Sea ◽  
Dust Particles ◽  
Chemical Compositions ◽  
Asian Dust Storm ◽  
Beijing China

Abstract. This is the first study of Asian dust storm (ADS) particles collected in Beijing, China, and Incheon, Korea, during a spring ADS event. Using a seven-stage May impactor and a quantitative electron probe X-ray microanalysis (ED-EPMA, also known as low-Z particle EPMA), we examined the composition and morphology of 4200 aerosol particles at stages 1–6 (with a size cut-off of 16, 8, 4, 2, 1, and 0.5 μm in equivalent aerodynamic diameter, respectively) collected during an ADS event on 28–29 April 2005. The results showed that there were large differences in the chemical compositions between particles in sample S1 collected in Beijing immediately after the peak time of the ADS and in samples S2 and S3, which were collected in Incheon approximately 5 h and 24 h later, respectively. In sample S1, mineral dust particles accounted for more than 88% in relative number abundance at stages 1–5; and organic carbon (OC) and reacted NaCl-containing particles accounted for 24% and 32%, respectively, at stage 6. On the other hand, in samples S2 and S3, in addition to approximately 60% mineral dust, many sea spray aerosol (SSA) particles reacted with airborne SO2 and NOx (accounting for 24% and 14% on average in samples S2 and S3, respectively), often mixed with mineral dust, were encountered at stages 1–5, and (C, N, O, S)-rich particles (likely a mixture of water-soluble organic carbon with (NH4)2SO4 and NH4NO3) were abundantly observed at stage 6 (accounting for 68% and 51% in samples S2 and S3, respectively). This suggests that an accumulation of sea-salt components on individual ADS particles larger than 1 μm in diameter occurred and many secondary aerosols smaller than 1 μm in diameter were formed when the ADS particles passed over the Yellow Sea. In the reacted or aged mineral dust and SSA particles, nitrate-containing and both nitrate- and sulfate-containing species vastly outnumbered the sulfate-containing species, implying that ambient NOx had a greater influence on the atmospheric particles than SO2 during this ADS episode. In addition to partially- or totally-reacted CaCO3, reacted or aged Mg-containing aluminosilicates were observed frequently in samples S2 and S3; furthermore, a student's t test showed that both their atomic concentration ratios of [Mg] / [Al] and [Mg] / [Si] were significantly elevated (P < 0.05) compared to those in samples S1 (for [Mg] / [Al], 0.34 ± 0.09 and 0.40 ± 0.03 in samples S2 and S3, respectively, vs. 0.24 ± 0.01 in sample S1; for [Mg] / [Si], 0.21 ± 0.05 and 0.22 ± 0.01 in samples S2 and S3, respectively, vs. 0.12 ± 0.02 in sample S1). The significant increase of [Mg] / [Al] and [Mg] / [Si] ratios in Mg-containing aluminosilicates indicates that a significant evolution or aging must have occurred on the ADS particles in the marine atmosphere during transport from China to Korea.

scholarly journals Dicarboxylic acids, oxoacids, benzoic acid, α-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

2015 ◽  
Vol 15 (18) ◽  
pp. 26509-26554 ◽  
Author(s):  
D. K. Deshmukh ◽  
K. Kawamura ◽  
M. Lazaar ◽  
B. Kunwar ◽  
S. K. R. Boreddy
Keyword(s):  
Organic Carbon ◽  
Benzoic Acid ◽  
North Pacific ◽  
Western North Pacific ◽  
Sea Salt ◽  
Water Soluble ◽  
Pacific Rim ◽  
Size Distributions ◽  
Coarse Mode ◽  
Fine Mode

Abstract. Size-segregated aerosols (9-stages from < 0.43 to > 11.3 μm in diameter) were collected at Cape Hedo, Okinawa in spring 2008 and analyzed for water-soluble diacids (C2–\\C12), ω-oxoacids (ωC2–ωC9), pyruvic acid, benzoic acid and α-dicarbonyls (C2–C3) as well as water-soluble organic carbon (WSOC), organic carbon (OC) and major ions. In all the size-segregated aerosols, oxalic acid (C2) was found as the most abundant species followed by malonic and succinic acids whereas glyoxylic acid (ωC2) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C2–C5), ωC2 and Gly as well as WSOC and OC peaked at 0.65–1.1 μm in fine mode whereas azelaic (C9) and 9-oxononanoic (ωC9) acids peaked at 3.3–4.7 μm in coarse mode. Sulfate and ammonium are enriched in fine mode whereas sodium and chloride are in coarse mode. These results imply that water-soluble species in the marine aerosols could act as cloud condensation nuclei (CCN) to develop the cloud cover over the western North Pacific Rim. The organic species are likely produced by a combination of gas-phase photooxidation, and aerosol-phase or in-cloud processing during long-range transport. The coarse mode peaks of malonic and succinic acids were obtained in the samples with marine air masses, suggesting that they may be associated with the reaction on sea salt particles. Bimodal size distributions of longer-chain diacid (C9) and oxoacid (ωC9) with a major peak in the coarse mode suggest their production by photooxidation of biogenic unsaturated fatty acids via heterogeneous reactions on sea salt particles.

scholarly journals Investigation of Three-Dimensional Evolution of East Asian Dust Storm by Modeling and Remote Sensing Measurements

2015 ◽  
Vol 2015 ◽  
pp. 1-12
Author(s):  
Jiawei Li ◽  
Zhiwei Han
Keyword(s):  
Dust Storm ◽  
East Asian ◽  
3D Structure ◽  
Three Dimensional ◽  
Asian Dust ◽  
East China ◽  
Gobi Desert ◽  
Air Quality Model ◽  
Quality Model ◽  
Asian Dust Storm

The three-dimensional evolution of an East Asian dust storm during 23–26 April 2009 was investigated by utilizing a regional air quality model system (RAQMS) and satellite measurements. This severe dust storm hit Mt. Tai in east China with daily mean PM10concentration reaching 1400 μg/m3and the model captured the PM10variation reasonably well. Modeled spatial distributions of AOD and vertical profiles of aerosol extinction coefficient during the dust storm were compared with MODIS and CALIPSO data, demonstrating that RAQMS was able to reproduce the 3D structure and the evolution of the dust storm reasonably well. During early days of the dust storm, daily mean dust-induced AOD exceeded 2.0 over dust source regions (the Gobi desert and the Taklamakan desert) and was in a range of 1.2–1.8 over the North China Plain, accounting for about 98% and up to 90% of total AOD over corresponding areas, respectively. The top of the dust storm reached about 8 km over east China, with high dust concentration locating at around 40°N. Dust aerosol below 2 km was transported southeastward off the Gobi desert while dust above 2 km was transported out of China along 40°–45°N.

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.

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