Asian Dust Storm Research Articles

제주지역 TSP 이온성분 농도의 장기 변화

The water-soluble components have been analyzed from the total suspended particulate (TSP) collected at Gosan site of Jeju Island for ten years (1997~2006), and the long-term variations of ionic constituent concentrations have been investigated in order to understand the pollution characteristics of atmospheric aerosols. Their mean concentrations were in the order of nss- > > > > > nss- > > . The concentrations had increased somewhat smoothly compared to those of for the past 10 years, possibly indicating the recent energy consumption pattern changes in China. The concentrations of ionic aerosol components showed mostly higher values during the Asian Dust storm periods, and the concentration ratios of nss-, , and nss- between the Asian Dust and Non-Asian Dust periods were 6.9, 2.4, and 1.3, respectively. The anthropogenic nss-, , and the soil originated nss- components showed high concentrations as the air parcels were moved from the Asia continent, on the other hand, their concentrations were relatively low as moving from the Northern Pacific into the Gosan area.

Development of a New Wind-Blown-Dust Emission Module Using Comparative Assessment of Existing Dust Models

A new wind-blown dust emission module has been fabricated to be used in investigating the development and transport of Asian dust storms. A number of different dust emission models currently used worldwide were critically compared to collect the state-of-the-art schemes for each parameterization step of the wind erosion process. Thorough assessment of the dust models were conducted with an aid of literature review to judge the advantages and drawbacks of each model. The threshold friction velocity for smooth dry surface, the drag partitioning effect by non-erodible surface roughness elements, the soil moisture effect, the positive feedback of the saltating soil particles to the friction velocity, the saltation scheme calculating the horizontal soil flux, and the sandblasting scheme calculating the vertical dust emission flux were considered. A new wind-blown dust emission model was developed using the best components determined based on the analyses of this study. The predictions of the size-resolved wind-blown dust emission by different models were compared for the first time with a field measurement available in the literature. The new model developed in this study showed a reasonably good agreement with the measurement (agreement index of 0.91).

Ambient Influenza and Avian Influenza Virus during Dust Storm Days and Background Days

BackgroundThe spread of influenza and highly pathogenic avian influenza (H5N1) presents a significant threat to human health. Avian influenza outbreaks in downwind areas of Asian dust storms (ADS) suggest that viruses might be transported by dust storms.ObjectivesWe developed a technique to measure ambient influenza and avian influenza viruses. We then used this technique to measure concentrations of these viruses on ADS days and background days, and to assess the relationships between ambient influenza and avian influenza viruses, and air pollutants.MethodsA high-volume air sampler was used in parallel with a filter cassette to evaluate spiked samples and unspiked samples. Then, air samples were monitored during ADS seasons using a filter cassette coupled with a real-time quantitative polymerase chain reaction (qPCR) assay. Air samples were monitored during ADS season (1 January to 31 May 2006).ResultsWe successfully quantified ambient influenza virus using the filtration/real-time qPCR method during ADS days and background days. To our knowledge, this is the first report describing the concentration of influenza virus in ambient air. In both the spiked and unspiked samples, the concentration of influenza virus sampled using the filter cassette was higher than that using the high-volume sampler. The concentration of ambient influenza A virus was significantly higher during the ADS days than during the background days.ConclusionsOur data imply the possibility of long-range transport of influenza virus.

The impact of dust on sulfate aerosol, CN and CCN during an East Asian dust storm

Abstract. A global model of aerosol microphysics is used to simulate a large East Asian dust storm during the ACE-Asia experiment. We use the model together with size resolved measurements of aerosol number concentration and composition to examine how dust modified the production of sulfate aerosol and the particle size distribution in East Asian outflow. Simulated size distributions and mass concentrations of dust, sub- and super-micron sulfate agree well with observations from the C-130 aircraft. Modeled mass concentrations of fine sulfate (Dp<1.3 μm) decrease by ~10% due to uptake of sulfur species onto super-micron dust. We estimate that dust enhanced the mass concentration of coarse sulfate (Dp>1.0 μm) by more than an order of magnitude, but total sulfate concentrations increase by less than 2% because decreases in fine sulfate have a compensating effect. Our analysis shows that the sulfate associated with dust can be explained largely by the uptake of H2SO4 rather than reaction of SO2 on the dust surface, which we assume is suppressed once the particles are coated in sulfate. We suggest that many previous model investigations significantly overestimated SO2 oxidation on East Asian dust, possibly due to the neglect of surface saturation effects. We extend previous model experiments by examining how dust modified existing particle concentrations in Asian outflow. Total particle concentrations (condensation nuclei, CN) modeled in the dust-pollution plume are reduced by up to 20%, but we predict that dust led to less than 10% depletion in particles large enough to act as cloud condensation nuclei (CCN). Our analysis suggests that E. Asian dust storms have only a minor impact on sulfate particles present at climate-relevant sizes.

Health Effects of Asian Dust Events: A Review of the Literature

Asian dust, called 'kosa' in Japan, is the long-range transport of atmospheric pollutants originating from the desert areas of China and Mongolia. Although Asian dust has a long history of appearing in Japan, it is only quite recently that there is increasing concern for its possible adverse health effects. We reviewed the epidemiologic evidence of potential health effects of Asian dust events. PubMed was used to search for the following keywords: Asian dust, yellow sand, desert dust, dust storm, sandstorm, mortality, death, morbidity, hospitalization, hospital admission, health, pulmonary and respiratory. The search was limited to the epidemiologic studies published between January 1980 and May 2009. JMEDPlus was used to search for Japanese literature. Seventeen studies were retrieved from PubMed and one study from JMEDPlus. In addition, one study was identified for reviewing from the references of another study. In total, we identified 19 epidemiologic studies (3 for mortality, 13 for hospital visits or admissions and 3 for respiratory functions or symptoms) mainly from Taiwan and Korea. There were many combinations of outcomes and lagged exposures examined, and some suggested possible associations of dust exposure with an increase in mortality and hospital visits and admissions due to cardiovascular and respiratory diseases, whereas the rest of the studies did not show statistically significant associations. The evidence from these studies was limited because exposure assessments were inadequately described and potential confounders were insufficiently controlled. Well-designed epidemiological studies are required to clarify any potential health effects of Asian dust events in Japan.

Asian Dust Storm Activity and Its Association with Atmospheric Circulation from 1995 to 2006

Asian Dust Storm Activity and Its Association with Atmospheric Circulation from 1995 to 2006

서해연안 도시지역의 대기질 특성 연구: 군산과 전주의 대기질 비교를 중심으로

This study is to investigate the air pollution characteristics of an industrialized midsize west-coastal city by comparing air quality to a neighboring inland city. The hourly averaged data of , , , CO, and measured from continuous air quality monitoring sites in Gunsan (coastal) and Jeonju (inland) were analyzed. The data set covers the period from 2004 to 2006. The annual average concentrations of the air pollutants in two cities were compared in their abundances and temporal trends as well. and in Gunsan were relatively higher than those in Jeonju, while vice versa in case of and . It seems that heavy automobile emissions from Jeonju mainly bring on higher and than those in Gunsan on annual base. concentrations in both cities showed bimodal diurnal variations with peaks in the morning and in the late evening. These peaks correspond to the coupled effects of rush hour traffic and meteorological conditions (i.e., variation of mixing height and dispersion conditions). Maximum hourly averages of ranged from 18 ppb to 28 ppb at Jeonju, and from 12 ppb to 20 ppb at Gunsan. showed typical diurnal variation with a maximum in the afternoon between 14:00 and 16:00 LST. Diurnal variations of CO and were similar to while was similar to . Seasonal variations of in both cities indicated that their concentrations during spring season were significantly high. Asian dust storms occur frequently during spring and seem to affect increase in . High and days were selected from both cities. The analyses based on the HYSPLIT trajectory model during the high and showed these episodes (six cases) were mostly coincident with Asian dust storm originated from northern China and Mongolia. However, these high air pollution episodes in the west coastal cities may not only be caused by the Asian dust but also affected by other air pollutants transported from China accompanying the Asian dust.

Asian Dust Storm and pulmonary function of school children in Seoul

Health effects of the Asian Dust Storm (ADS) have not been evaluated adequately, even though it may affect health of people in East Asia. This study was conducted to evaluate whether the ADS affects particulate air pollution and pulmonary function of children. We studied 110 school children in Seoul, Korea with daily measurement of peak expiratory flow rate (PEFR) from May 13 to June 15, 2007. PM 2.5, PM 10 and metals bound to the particles were also determined daily during the study period in Ala Shan and Beijing (China) as well as in Seoul (Korea). Three-day back trajectories showed that air parcels arrived at Seoul mostly from the desert areas in China and Mongolia through eastern China during ADS event affecting levels of particulate pollutants in the areas. Analysis of metals bound to the particulates showed that natural metal levels were much higher than the anthropogenic metal levels. We found that ambient concentrations of PM 2.5 and PM 10 were not significantly associated with PEFR in school children except asthmatics during the study period ( P > 0.05). However, most of the metal concentrations bound to the particulates were significantly associated with decrease of the children's PEFR ( P < 0.05). The effect of anthropogenic metals was not different from natural components of metals for reduction of PEFR. This result indicates that exposure to the metals bound to particles during the ADS period reduces children's pulmonary function, but there was no difference of potency for reduction of the pulmonary function between natural and anthropogenic metal components.

Asian Dust Storms and Pulmonary Function of School Children

ISEE-0181 Background: Health effects of Asian Dust Storm (ADS) have not been evaluated adequately, even though it may affect health of people in East Asia. This study was conducted to evaluate whether the ADS affects the particulate air pollution and the pulmonary function of children. Methods: We studied 335 school children in three cities (Ala Shan and Beijing in China and Seoul in Korea), with daily measurement of PEFR from May 13 to June 15, 2007. PM2.5 (particulate with aerodynamic diameter < 2.5 μm), PM10 (< 10 μm) and their metal components were also determined daily. Results: ADS arrived at Seoul mostly from the desert areas through eastern China. We found that ambient concentrations of PM2.5 and PM10 for each city were not significantly associated with PEFR in school children during the study period (P>0.05). However, most of the metal concentrations bound to the particulates were significantly associated with increase of the children's PEFR in Beijing (P<0.05), whereas they were significantly associated with decrease of the PEFR in Seoul (P<0.05). The lag distribution of the PEFR change by metal concentrations showed almost symmetrically opposite patterns of the effect between Beijing and Seoul. Conclusion: This result indicates that ADS affects the concentrations of particulate air pollutants, and the effect on pulmonary function of school children varies depending on the locations of cities along the paths of the ADS. This study suggests that the ADS contribute to displacement of urban air pollution and the health effect from eastern China to Korea.

Characteristics of aerosol dust in fresh snow in the Asian dust and non-dust periods at Urumqi glacier no. 1 of eastern Tian Shan, China

Windblown mineral aerosol dust derived from the crustal surface is an important atmospheric component affecting the earth’s radiation budget. Deposition of atmospheric dust was measured in the fresh snow on glacier no. 1 at the headwater of the Urumqi River in eastern Tian Shan, central Asia. An analysis of seasonal variation of concentrations of dust particles in the snow suggests that the number concentration of dust particle is significantly high from April to June, which may be caused by Asian dust storms in the spring. The comparison of mass-size distribution of dust particles from April to August shows an obvious seasonal change trend. The distribution of particles changes from single model (3–21 μm) in the non-dust period before dust events in April, to bi-model (3–21 and 20–80 μm) during the Asian dust period, and to single model (3–21 μm) after July in the non-dust period again. The Ca2+ concentration in the fresh snow is also very high from April to June, while NH4+ and SO42−, as water-soluble constituents, have concentration changes that are different from each other. Backward trajectory was also employed to examine the transport process of air mass in this region.

Elevated nitrogen-containing particles observed in Asian dust aerosol samples collected at the marine boundary layer of the Bohai Sea and the Yellow Sea

Abstract. Low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA) shows powerful advantages for the characterization of ambient particulate matter in environmental and geological applications. By the application of the low-Z particle EPMA single particle analysis, an overall examination of 1800 coarse and fine particles (aerodynamic diameters: 2.5–10 μm and 1.0–2.5 μm, respectively) in six samples collected on 28 April–1 May 2006 in the marine boundary layer (MBL) of the Bohai Sea and Yellow Sea was conducted. Three samples (D1, D2, and D3) were collected along the Bohai Bay, Bohai Straits, and Yellow Sea near Korea during an Asian dust storm event while the other three samples (N3, N2, and N1) were collected on non-Asian dust (NAD) days. Based on X-ray spectral and secondary electron image data, 15 different types of particles were identified, in which soil-derived particles were encountered with the largest frequency, followed by (C, N, O)-rich droplets (likely the mixture of organic matter and NH4NO3), particles of marine origin, and carbonaceous, Fe-rich, fly ash, and (C, N, O, S)-rich droplet particles. Results show that during the Asian dust storm event relative abundances of the (C, N, O)-rich droplets and the nitrate-containing secondary soil-derived particles were markedly increased (on average by a factor of 4.5 and 2, respectively in PM2.5−10 fraction and by a factor of 1.9 and 1.5, respectively in PM1.0−2.5 fraction) in the MBL of the Bohai Sea and Yellow Sea, implying that Asian dust aerosols in springtime are an important carrier of gaseous inorganic nitrogen species, especially NOx (or HNO3) and NH3.

Indoor and outdoor PM 2.5 and PM 10 concentrations in the air during a dust storm

Asian dust storms (ADS) originating from the arid deserts of Mongolia and China are a well-known springtime meteorological phenomenon throughout East Asia. The ventilation systems in office utilize air from outside and therefore it is necessary to understand how these dust storms affect the concentrations of PM 2.5 and PM 10 in both the indoor and outdoor air. We measured dust storm pollution particles in an office building using a direct-reading instrument (PC-2 Quartz Crystal Microbalance, QCM) that measured particle size and concentration every 10 min for 1 h, three times a day. A three-fold increase in the concentrations of PM 2.5 and PM 10 in the indoor and outdoor air was recorded during the dust storms. After adjusting for other covariates, autoregression models indicated that PM 2.5 and PM 10 in the indoor air increased significantly (21.7 μg/m 3 and 23.0 μg/m 3 respectively) during dust storms. The ventilation systems in high-rise buildings utilize air from outside and therefore the indoor concentrations of fine and coarse particles in the air inside the buildings are significantly affected by outside air pollutants, especially during dust storms.

Exposure of acid aerosol for schoolchildren in metropolitan Taipei

Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO 2, SO 2, HNO 3, NO 3 −, SO 4 2−, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 μg m −3, 18.5 μg m −3, and 49.5 nmol m −3 in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 μg m −3, 8.8 μg m −3 and 14.7 nmol m −3 in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO 2 levels were low (0.13–8.03 ppb) in the metropolitan Taipei. However, the SO 4 2− concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed.

Numerical simulations of Asian dust storms using a coupled climate‐aerosol microphysical model

We have developed a three‐dimensional coupled microphysical/climate model based on the National Center for Atmospheric Research Community Atmospheres Model and the University of Colorado/NASA Community Aerosol and Radiation Model for Atmospheres. We have used the model to investigate the sources, removal processes, transport, and optical properties of Asian dust aerosol and its impact on downwind regions. The model simulations are conducted primarily during the time frame of the Aerosol Characterization Experiment–Asia field experiment (March–May 2001) since considerable in situ data are available at that time. Our dust source function follows Ginoux et al. (2001). We modified the dust source function by using the friction velocity instead of the 10‐m wind based on wind erosion theory, by adding a size‐dependent threshold friction velocity following Marticorena and Bergametti (1995) and by adding a soil moisture correction. A Weibull distribution is implemented to estimate the subgrid‐scale wind speed variability. We use eight size bins for mineral dust ranging from 0.1 to 10 μm radius. Generally, the model reproduced the aerosol optical depth retrieved by the ground‐based Aerosol Robotic Network (AERONET) Sun photometers at six study sites ranging in location from near the Asian dust sources to the Eastern Pacific region. By constraining the dust complex refractive index from AERONET retrievals near the dust source, we also find the single‐scattering albedo to be consistent with AERONET retrievals. However, large regional variations are observed due to local pollution. The timing of dust events is comparable to the National Institute for Environmental Studies (NIES) lidar data in Beijing and Nagasaki. However, the simulated dust aerosols are at higher altitudes than those observed by the NIES lidar.

Isotopic evidences for provenance of East Asian Dust

We have systematically collected samples in the possible source regions (the deserts and sandy lands of North China, northeastern past of the Tibetan Plateau, Chinese Loess Plateau and southern part of Mongolia) of the East Asian dust. Based on Nd–Sr isotopic ranges, the source regions can be divided into four isotopic regions: Region A1: the Gurbantunggut Desert in Junggar basin and Hunlun Buir sandy land in northeastern China; Region A2: the Hunshandake sandy land, Horqin sandy land and southern part of Mongolia; Region B: the Taklimakan Desert in Tarim basin, northeastern past of the Tibetan Plateau, Chinese Loess Plateau, Badain Jaran Desert and Tengger Desert in Alashan Plateau; Region C: the Hobq Desert and Mu Us Desert in the Ordos Plateau. Through comparison of Nd–Sr isotopes, it can be inferred that the sediments of the north-central Pacific and dust particles in the Greenland ice cores are mainly derived from Region B. Dusts of East Asian dust storm are derived mostly from Region B also, and less from Region A2. The materials of dust storm at Beijing area in April 2006, originated largely from the Hobq Desert and Mu Us Desert in the Ordos Plateau. The floating dust at Beijing area in April 2006, is the mixing of dust of distant deserts and local dust at Beijing area. Loess of the Chinese Loess Plateau may largely originate from Region B.

Quantitative ED-EPMA combined with morphological information for the characterization of individual aerosol particles collected in Incheon, Korea

A quantitative single-particle analytical technique, called low- Z particle electron probe X-ray microanalysis, combined with the utilization of their morphological information on individual particles, was applied to characterize six aerosol samples collected in one Korean city, Incheon, during March 9–15, 2006. The collected supermicron aerosol particles were classified based on their chemical species and morphology on a single-particle basis. Many different particle types were identified and their emission source, transport, and reactivity in the air were elucidated. In the samples, particles in the “soil-derived particles” group were the most abundant, followed by “reacted sea-salts”, “reacted CaCO 3-containing particles”, “genuine sea-salts”, “reacted sea-salts + others”, “Fe-containing particles”, “anthropogenic organics”, (NH 4) 2SO 4, “K-containing particles”, and “fly ash”. The application of this single-particle analysis, fully utilizing their chemical compositional and morphological data of individual particles, clearly revealed the different characteristics of the six aerosol samples. For samples S3 and S5, which were sampled during two Asian dust storm events, almost all particles were of soil origin that had not experienced chemical modification and that did not entrain sea-salts during their long-range transport. For sample S1, collected at an episodic period of high PM 10 concentration and haze, anthropogenic, secondary, and soil-derived particles emitted from local sources were predominant. For samples S2, S4, and S6, which were collected on average spring days with respect to their PM 10 concentrations, marine originated particles were the most abundant. Sample S2 seems to have been strongly influenced by emissions from the Yellow Sea and Korean peninsula, sample S4 had the minimum anthropogenic influence among the four samples collected in the absence of any Asian dust storm event, and sample S6 seems to have entrained air pollutants that had been transported from mainland China over the Yellow Sea to Korea.

Reactivity between PbSO 4 and CaCO 3 particles relevant to the modification of mineral particles and chemical forms of Pb in particles sampled at two remote sites during an Asian dust event

During the transboundary transport of anthropogenic heavy metals by mineral particles providing reaction sites, the divalent metal salt PbSO 4 can be converted to PbCO 3 in the presence of water. We carried out laboratory experiments to study the transformation process under various conditions by incorporating test particles comprising CaCO 3 of a particulate mineral component, PbSO 4, and NaCl. After the immersion of PbSO 4 particles in contact with CaCO 3 particles in a water droplet, the conversion of PbSO 4 into PbCO 3 was confirmed by the change in morphology of the original particles to stick or needle form; the percentages of the chemical forms relative to the total Pb were determined by X-ray absorption near edge structure (XANES) analysis. Approximately 60–80% of PbSO 4 was converted to PbCO 3 after 24 h. A small amount of stick particles was detected when NaCl particles attached to PbSO 4/CaCO 3 particles were exposed to air with a relative humidity (RH) of 80–90% for 24 h. XANES measurements of the samples revealed that the molar percentage of PbCO 3 relative to the total Pb content was 4%. Field experiments were also conducted to determine the chemical forms of the Pb particles during the Kosa (Asian dust storm) event. Samples were collected from two remote sites in Japan and Korea. The mass size distribution of Pb aerosols collected in Japan was bimodal with two peaks in the coarse mode; the enrichment factor of Pb suggested that its source was anthropogenic. Pb L3 edge XANES measurements of both samples indicated that they had similar shapes. These measurements also indicated that the major Pb components for the samples collected in Japan were PbO, PbSO 4 PbCl 2, and PbCO 3, with molar percentages of 44%, 30%, 21%, and 5%, respectively. No significant differences were found between the component ratios of the samples collected in Japan and Korea, suggesting that definite transformation did not occur during the transport of the Kosa particles from Korea to Japan. On the basis of these observations, we postulate that the transformation process either occurred mainly before the particles arrived at Korea or did not take place after the particles left continental Asia.

Asian Dust particles impacts on air quality and radiative forcing over Korea

Asian Dust particles originated from the deserts and loess areas of the Asian continent are often transported over Korea, Japan, and the North Pacific Ocean during spring season. Major air mass pathway of Asian dust storm to Korea is from either north-western Chinese desert regions or north-eastern Chinese sandy areas. The local atmospheric environment condition in Korea is greatly impacted by Asian dust particles transported by prevailing westerly wind. Since these Asian dust particles pass through heavily populated urban and industrial areas in China before it reach Korean peninsular, their physical, chemical and optical properties vary depending on the atmospheric conditions and air mass pathway characteristics. An integrated system approach has been adopted at the Advanced Environment Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST), Korea for effective monitoring of atmospheric aerosols utilizing various in-situ and optical remote sensing methods, which include a multi-channel Raman LIDAR system, sunphotometer, satellite, and in-situ instruments. Results from recent studies on impacts of Asian dust particles on local air quality and radiative forcing over Korea are summarized here.

황사 에피소드 발생시 대기먼지의 농도 특성과 인체 영향

The Asian dust storms which originated in the deserts of Mongolia and China transported particles to Korea and led to a high concentration of atmospheric particulate matters (PM) of more than <TEX>$1000{\mu}g/m^3$</TEX> throughout the country in the spring, of 2007. Public concern, in Korea, about the possible adverse effects of these dust events has increased, as these dust storms can contain various air pollutants emitted from heavily industrialized eastern China. The objectives of this study were to understand the concentration characteristics of PM as a function of particle size between the Asian dust storm episodes and non-Asian dust period and to consider the mass size distribution of PM in the Asian dust storms and their water soluble ion species on the potential, possible effects on deposition levels in the three regions (nasopharyngeal, tracheobronchial, and alveolar) of the human respiratory system. The size distribution of PM mass concentration during the Asian dust storms showed a peak in the coarse particle region due to the long-range transport of soil particles from the deserts of Mongolia and China, which was identified by HYSPLIT-4 model for backward trajectory analysis of air arriving in the sampling site of Iksan. During the non-Asian dust period, there were two different types in PM size distribution: bimodal distribution when low concentrations of <TEX>$PM_{2.5}$</TEX> were observed, while unimodal distribution having a peak in fine particle region when high concentrations of <TEX>$PM_{2.5}$</TEX> were showed. This unimodal distribution with high concentrations of fine particulate and secondary air pollutants such as <TEX>${SO_4}^{2-}$</TEX>, <TEX>${NO_3}^-$</TEX>, <TEX>${NH_4}^+$</TEX> was found to be due to the long-range transport of air pollutants from industrialized eastern China. During the Asian dust storms, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were <TEX>$128.8{\mu}g/m^3$</TEX>, <TEX>$216.5{\mu}g/m^3$</TEX>, and <TEX>$89.6{\mu}g/m^3$</TEX>, respectively. During the non-Asian dust period, the mean concentrations of PM that can be deposited in the nasopharyngeal, tracheobronchial, and alveolar region were <TEX>$8.4{\mu}g/m^3$</TEX>, <TEX>$9.5{\mu}g/m^3$</TEX> and <TEX>$38.5{\mu}g/m^3$</TEX>, respectively.

Impacts of Asian dust storm associated with the stratosphere-to-troposphere transport in the spring of 2001 and 2002 on dust and tritium variations in Mount Wrangell ice core, Alaska

The relation of interannual connection between Asian dust outbreaks and stratosphere-to-troposphere transport (STT) in spring was suggested by the dust and tritium variations in the Mount Wrangell ice core, Alaska in [Yasunari, T.J., Shiraiwa, T., Kanamori, S., Fujii, Y., Igarashi, M., Yamazaki, K., Benson, C.S., Hondoh, T., 2007. Intra-annual variations in atmospheric dust and tritium in the North Pacific region detected from an ice core from Mount Wrangell, Alaska. J. Geophys. Res., 112, D10208. doi: 10.1029/2006JD008121]. However, these impacts on the ice core site in each event scale have not been investigated. Hence, the present paper focuses on the material transport and deposition processes for further understanding these impacts on the ice core. The variations in dust and tritium concentrations in spring in an ice core taken at Mt. Wrangell, Alaska are explained by meteorological analysis and simulation of trajectories associated with Asian dust outbreaks and STT. Material transport and deposition at Mt. Wrangell are examined in two contrasting years (2001 and 2002). Dust and tritium concentrations both reached peak values in the early spring of 2002, while the dust peak occurred in early spring and the tritium peak occurred in late spring in 2001. Six severe East Asian transpacific dust storms over this period are modeled by forward trajectory and meteorologically analyzed. It is found that 5 of 6 events contributed to the ice core record in Alaska. Stratospheric air is also transported to the ice core site in most cases. Tritium deposition is found to have been suppressed in the cases of the 2001 dust storms due to lack of snowfall at appropriate times. Taken the detailed transport and deposition processes after the severe dust storms with atmospheric circulations into account, we can well explain spring dust and tritium variations in the Mount Wrangell ice core.