Asian Dust Events Research Articles

Iron fertilisation by Asian dust influences North Pacific sardine regime shifts

Forcing factors and mechanisms underlying multidecadal variability in the production of the world’s major fish stocks are one of the great mysteries of the oceans. The Japanese and California sardine are species that exhibit the regime shifts. It is shown in the present work that during two periods of frequent Asian dust events over the last 100years, sardines on opposite sides of the Pacific Ocean only flourished under a dust-active regime. The earlier such regime that peaked in the 1930s was strong, and it brought synchronous changes in the two species that were linked to the frequency of Asian dust events. However, there is an apparent mismatch in the rise and fall of abundance between the two species in the current dust-active regime. The massive increase in Japanese sardine stock in the 1970s was related to high levels of ocean precipitation and strong winter mixing, whereas the stock collapse since 1988 has been attributed to diminished winter mixing. High levels of ocean precipitation in the western North Pacific effectively cause wet deposition of Asian dust and enhance Japanese sardine stock, whereas it reduces dust flux that can be transported to the eastern North Pacific, delaying the increase of California sardine stock. Analysis further indicates that productivity of Japanese sardine stock is jointly controlled by wet deposition of Asian dust and winter mixing, which supplies macronutrients from depth. California sardine productivity is inversely related to precipitation in the western North Pacific and is positively affected by precipitation off western North America. This indicates that Asian dust influx dominates productivity of the species because of iron-limited ocean productivity in the California sardine ranges. The analysis suggests that dust regime shifts influence shifts in sardine productivity regimes and that iron input from Asian dust during trans-Pacific transport is directly responsible. It appears that in addition to enhancing phytoplankton growth and carbon sinks, atmospheric iron deposition can regulate the production of living ocean resources, which is an extension of Martin’s iron hypothesis.

WRF-Chem 모델을 이용한 2010년 한반도의 황사 예측에 관한 연구

The WRF-Chem model was applied to simulate the Asian dust event affecting the Korean Peninsula from 11 to 13 November 2010. GOCART dust emission schemes, RADM2 chemical mechanism, and MADE/SORGAM aerosol scheme were adopted within the WRF-Chem model to predict dust aerosol concentrations. The results in the model simulations were identified by comparing with the weather maps, satellite images, monitoring data of concentration, and LIDAR images. The model results showed a good agreement with the long-range transport from the dust source area such as Northeastern China and Mongolia to the Korean Peninsula. Comparison of the time series of concentration measured at Backnungdo showed that the correlation coefficient was 0.736, and the root mean square error was . The spatial distribution of concentration using the WRF-Chem model was similar to that of the which were about a half of . Also, they were much alike in those of the UM-ADAM model simulated by the Korean Meteorological Administration. Meanwhile, the spatial distributions of concentrations during the Asian dust events had relevance to those of both the wind speed of u component () and the PBL height (m). We performed a regressive analysis between concentrations and two meteorological variables (u component and PBL) in the strong dust event in autumn (CASE 1, on 11 to 23 March 2010) and the weak dust event in spring (CASE 2, on 19 to 20 March 2011), respectively.

Ground‐based measurement of fluorescent aerosol particles in Tokyo in the spring of 2013: Potential impacts of nonbiological materials on autofluorescence measurements of airborne particles

AbstractWe present results from the observation of fluorescent (FL) aerosols in Tokyo in the spring of 2013. Ambient aerosol particles were analyzed using a single‐particle laser‐induced fluorescence instrument. The fluorescent emission from a single particle excited by a pulsed UV laser (excitation wavelength of 263 nm) was detected by three photomultiplier tubes with band‐pass filters (fluorescence wavelength of 335–379, 420–500, and 500–600 nm). Fluorescence patterns from single particles were analyzed for investigating fluorophores and their sources using backward trajectory analysis, factor analysis, and a comparison with other tracer observations. The backward trajectory analysis suggested possible influences of long‐range transport from northern China in some cases. Observed supermicron FL aerosols were classified into two types: combustion‐ and dust‐type particles. The detection of combustion‐type FL aerosols, which showed temporal variations similar to nitrogen oxides and elemental carbon, implied the presence of polyaromatic hydrocarbons (PAHs) and their derivatives. Dust‐type FL aerosols, which were well correlated with the lidar‐derived dust‐aerosol optical depth near the surface (<1 km) and with mineral ions, were dominant in the supermicron size range. The number concentrations of coarse FL aerosols (≥2 µm), with which nonnegligible levels of fluorescence were recorded in all three channels, increased during Asian dust events (relative to a local dust event). It is suggested that PAHs and/or biological materials mixed with dust particles were transported from the North China Plain to the outflow region in East Asia during the observation period. Moreover, the autofluorescence measurement of airborne particles can be substantially affected by nonbiological materials in this region.

The relationship between Asian dust events and out-of-hospital cardiac arrests in Japan.

BackgroundAsian dust events are caused by dust storms that originate in the deserts of China and Mongolia and drift across East Asia. We hypothesized that the dust events would increase incidence of out-of-hospital cardiac arrests by triggering acute events or exacerbating chronic diseases.MethodsWe analyzed the Utstein-Style data collected in 2005 to 2008 from seven prefectures covering almost the entire length of Japan to investigate the effect of Asian dust events on out-of-hospital cardiac arrests. Asian dust events were defined by the measurement of light detection and ranging. A time-stratified case-crossover analysis was performed. The strength of the association between Asian dust events and out-of-hospital cardiac arrests was shown by odds ratios and 95% confidence intervals in two conditional logistic models. A pooled estimate was obtained from area-specific results by random-effect meta-analysis.ResultsThe total number of cases of out-of-hospital cardiac arrest was 59 273, of which 35 460 were in men and 23 813 were in women. The total number of event days during the study period was smallest in Miyagi and Niigata and largest in Shimane and Nagasaki. There was no significant relationship between Asian dust events and out-of-hospital cardiac arrests by area in either of the models. In the pooled analysis, the highest odds ratios were observed at lag day 1 in both model 1 (OR 1.07; 95% CI, 0.97–1.19) and model 2 (OR 1.08; 95% CI, 0.97–1.20). However, these results were not statistically significant.ConclusionsWe found no evidence of an association between Asian dust events and out-of-hospital cardiac arrests.

Temporal and Spatial Variations in Fine and Coarse Particles in Seoul, Korea

Concentrations of fine (PM2.5) and coarse (PM10–2.5) particles, whose aerodynamic diameters are less than or equal to 2.5 µm, and greater than 2.5 and less than or equal to 10 µm, respectively, at ambient air monitoring stations in Seoul between 2002 and 2008 were analyzed. Effects of Asian dust are mainly manifested as concentration spikes of PM10–2.5, but were considerable on PM2.5 levels in 2002 when Asian dust storms were the strongest. Excluding the effects of Asian dust, annual average PM2.5 showed a downward trend. Despite a similarity in year-to-year variations, PM10–2.5, mostly affected by fugitive dust emissions, and CO and NO2, primarily affected by motor vehicle emissions, did not show a decrease. PM2.5 along with CO and NO2 had peak concentration during the morning rush hour; the PM10–2.5 peak lagged one hour behind the PM2.5 peak. On high PM2.5 days, PM2.5 peaks occurred two hours later than usual as the effects of secondary formation through photochemical reactions became more important. A test for the spatial variability shows that PM10–2.5, which is known to be greatly influenced by local effects, is lower in its correlation coefficient and higher in its coefficient of divergence (COD, which serves as an indicator for spatial variability) than PM2.5, albeit by only a small difference. The average COD of PM2.5 among monitoring stations was about 0.2 but was lowered to 0.13 when considering high PM2.5 days only, signifying that spatial uniformity increases due to the pervasive influence of photochemical reactions.

Seasonal Fluctuations in Air Pollution in Dazaifu, Japan, and Effect of Long-Range Transport from Mainland East Asia.

To clarify the seasonal fluctuations in air pollution and the effect of long-range transport, we collected airborne particles (n=118) at Dazaifu in Fukuoka, Japan, from June 2012 to May 2013 and measured Pb and SO4(2-), which are indicators of the long-range transport of anthropogenic air pollutants, as well as their mutagenicity, and other factors. The levels of airborne particles, Pb, and SO4(2-) were very high on March 4, 8, 9, and 19, and May 13, 21, and 22, 2013. The backward trajectories indicated that air masses had arrived from the Gobi Desert and northern China on those days. The mutagenicity of airborne particles was examined using the Ames test on Salmonella typhimurium YG1024. Highly mutagenic airborne particles were mostly collected in winter, and most of them showed high activity both with and without S9 mix. High levels of polycyclic aromatic hydrocarbons (PAHs) were found in many samples that showed high mutagenicity. For the samples collected on January 30, February 21, and March 4, the levels of Pb, SO4(2-), PAHs, and mutagenicity were high, and the backward trajectories indicated that air masses present on those days had passed through northern or central China. The Japan Meteorological Agency registered Asian dust events at Fukuoka on March 8, 9, and 19, 2013. The results of the present study suggest that high levels of anthropogenic air pollutants were transported with Asian dust. Similarly, long-range transport of air pollutants including mutagens occurred on days when Asian dust events were not registered.

Effect of Observation Network Design on Meteorological Forecasts of Asian Dust Events

Abstract To improve the prediction of Asian dust events on the Korean Peninsula, meteorological fields must be accurately predicted because dust transport models require them as input. Accurate meteorological forecasts could be obtained by integrating accurate initial conditions obtained from data assimilation processes in numerical weather prediction. In data assimilation, selecting the appropriate observation location is important to ensure that the initial conditions represent the surrounding meteorological flow. To investigate the effect of observation network configuration on meteorological forecasts during Asian dust events on the Korean Peninsula, observing system simulation experiments using several simulated and real observation networks were tested with the Weather Research and Forecasting modeling system for 11 Asian dust events affecting the Korean Peninsula during a recent 6-yr period. First, the characteristics of randomly fixed and adaptively selected observation networks were investigated with various observation densities. The adaptive observation strategy could reduce forecast errors more efficiently than the fixed observation strategy. For both the fixed and adaptive observation strategies, the mean forecast error reduction rates increased as the number of assimilated observations and the distance between observation sites increased up to 300 km. Second, the effects of redistributing the real observation sites and adding observation sites to the real observation network based on the adaptive observation strategy were investigated. Adding adaptive observation sites to the real observation network in statistically sensitive regions improved the forecast performance more than redistributing real observation sites did. The strategy of adding adaptive observation sites is used to suggest the optimal meteorological observation network for meteorological forecasts of Asian dust transport events on the Korean Peninsula.

Asian dust and daily emergency ambulance calls among elderly people in Japan: an analysis of its double role as a direct cause and as an effect modifier.

To evaluate the direct health effects of Asian dust on ambulance calls and its role as an effect modifier on the effects of anthropogenic air pollution in Japan. The subjects were 51,945 elderly residents who visited hospital emergency departments from 2006 to 2010. We evaluated the impact of Asian dust by time-series analyses and the excess risk from suspended particulate matter (SPM) stratified by Asian-dust exposure. Asian dust was associated with daily ambulance calls due to all-cause, cardiovascular, and respiratory disease independently of SPM, for example, the relative risk per interquartile increase in Asian dust (3-day lag) was 1.021 (1.002 to 1.039) for cardiovascular disease. Furthermore, Asian dust modified the effects of SPM on cardiovascular and respiratory diseases. Asian dust had adverse effects and modified the effect of SPM.

광주지역 고농도 및 황사 시의 미세먼지 화학적 성분 특성

The aerosol characteristics between haze episode and Asian dust event were identified in January and March, 2013 in Gwang-ju of Korea to investigate the metal elements, ionic concentrations and carbonaceous particles of and . In the haze episode, the concentrations were increased 1~3.2 times of ionic species and 1.6~2.7 of metal elements. Especially, the concentration of , and consists of 50 percent in ionic species during haze episode that was higher than Asian dust event. This suggests that secondary aerosols from anthropogenic air pollution were mainly contributed by haze episode. During the Asian dust event, increase of metal concentrations was higher than haze episode because of remarkable increase of Ti, K and Fe originated from soil. The concentrations of carbonaceous particles were increased 2.5 times during haze episode, and 2.4 times of OC and 2.1 times of EC during Asian dust event in . However, these aerosol mass concentration does not affect the OC/EC ratio. The average equivalence ratios of cations/anions in were 0.99 in haze episodes and 0.94 during non-event day. The neutralization factor of was higher than that of . Futhermore, aerosol was aged due to atmospheric stagnation that might be affected by the haze episode.

Health Effects of Asian Dust: a Systematic Review

Background: There is increasing concern about the possible adverse health effects of Asian dust, but it has not been systematically studied. Aims: To identify and summarize potential health effects...

Reprint of: Effects of Asian dust on daily cough occurrence in patients with chronic cough: A panel study

Asian dust, known as kosa in Japanese, is a major public health concern. In this panel study, we evaluated the effects of exposure to kosa on daily cough occurrence. The study subjects were 86 patients being treated for asthma, cough variant asthma, or atopic cough in Kanazawa University Hospital from January 2011 to June 2011. Daily mean concentrations of kosa and spherical particles were obtained from light detection and ranging (LIDAR) measurements, and were categorized from Grade 1 (0 μg/m3) to 5 (over 100 μg/m3). The association between kosa and cough was analyzed by logistic regression with a generalized estimating equation. Kosa effects on cough were seen for all Grades with potential time lag effect. Particularly at Lag 0 (the day of exposure), a dose-response relationship was observed: the odds ratios for Grades 2, 3, 4, and 5 above the referent (Grade 1) were 1.111 (95% confidence interval (CI): 0.995-1.239), 1.171 (95% CI: 1.006-1.363), 1.357 (95% CI: 1.029-1.788), and 1.414 (95% CI: 0.983-2.036), respectively. Among the patients without asthma, the association was higher: the odds ratios for Grades 2, 3, 4 and 5 were 1.223 (95% CI: 0.999-1.497), 1.309 (95% CI: 0.987-1.737), 1.738 (95% CI: 1.029-2.935) and 2.403 (95% CI: 1.158-4.985), respectively. These associations remained after adjusting for the concentration of spherical particles or particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5). Our findings demonstrate that kosa is an environmental factor which induces cough in a dose-response relationship.

Reprint of: Number concentrations and elemental compositions of aerosol particles observed at Mt. Kiso-Komagatake in central Japan, 2010–2013

Aerosols in the lower troposphere over Japan are considered being influenced by those transported from Asian continent by westerly winds. In this study, we investigated the seasonal variation of aerosol number concentrations measured by means of optical particle counters at Mt. Kiso-Komagatake (2610 m altitude) in central Japan during the period from January 2010 to May 2013. We also collected aerosol samples in different seasons during part of the observation period and investigated their elemental compositions using transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX). The seasonal variation of the number concentrations suggested that accumulation-mode particles (particle diameter > 0.3 μm) increased during late spring perhaps owing to gas-to-particle conversion by means of photochemical reactions. The number concentrations of supermicron particles (>1 μm) were highest in spring, during which Asian dust events were frequent. Short-duration spikes in aerosol number concentrations, which were attributed to long-range transport from the Asian continent, were frequently observed in all seasons except summer. TEM analysis indicated that sulfate was the predominant component of accumulation-mode particles throughout the year. The number fraction of carbonaceous particles was also considerable, especially in samples in fall. The predominant components of supermicron particles collected during winter, spring and fall, and summer were sulfate, minerals, and sea salt, respectively. Our results suggest that the lower tropospheric air over central Japan is strongly influenced by long-range transport of aerosols in all seasons except summer.

Associations between subjective symptoms and serum immunoglobulin E levels during Asian dust events.

Asian dust is a seasonal meteorological phenomenon caused by the displacement of atmospheric pollutants from the Mongolian and Chinese deserts. Although the frequency of Asian dust events and atmospheric dust levels have steadily increased in the eastern Asia region, the effects on human health remain poorly understood. In the present study, the impact of Asian dust on human health was determined in terms of allergic reactions. A total of 25 healthy volunteers were tested for a relationship between serum immunoglobulin E (IgE) levels and subjective symptoms during a 3-day Asian dust event recorded in April 2012. They filled daily questionnaires on the severity of nasal, pharyngeal, ocular, respiratory, and skin symptoms by a self-administered visual analog scale. Serum levels of non-specific IgE and 33 allergen-specific IgE molecules were analyzed. Spearman rank-correlation analysis revealed significant positive associations between nasal symptom scores and 2 microbial-specific IgE levels (Penicillium and Cladosporium). Microbes migrate vast distances during Asian dust events by attaching themselves to dust particles. Therefore, some of these symptoms may be associated with type 1 allergic reactions to certain type of microbes.

Desert dust is a risk factor for the incidence of acute myocardial infarction in Western Japan.

Recently, there has been increasing concern about adverse health effects of exposure to desert dust events. However, the association between dust and the incidence of ischemic heart diseases is unknown. The aim of the present study was to elucidate whether Asian dust (AD), a windblown sand dust originating from mineral soil in China and Mongolia, is associated with the incidence of acute myocardial infarction (AMI). We investigated the data regarding hospitalization because of AMI among 3068 consecutive patients from 4 AMI centers in Fukuoka, Japan, and data for AD from April 2003 to December 2010. We applied a time-stratified case-crossover design to examine the association between AD and the incidence of AMI. Using a conditional logistic regression analysis, we estimated the odds ratios of AMI associated with AD after controlling for ambient temperature and relative humidity. The occurrence of AD events 0 to 4 days before the day of admission was significantly associated with the incidence of AMI. In particular, the occurrence of AD 4 days before admission was significantly associated with the onset of AMI. These data suggest that exposure to AD a few days before symptom onset is associated with the incidence of AMI.

Application of a satellite-based aridity index in dust source regions of northeast Asia

A modified temperature-vegetation dryness index based on land-surface temperature was used to represent land-surface aridity in northeast Asia. Past results indicated that saltation activity and dust emission did not often occur in northeast Asia when soil water content was greater than 4% and normalized soil water content was greater than 0.2. The threshold value of the modified temperature-vegetation dryness index for dust emissions was assumed to be 0.8 when the normalized soil water content was 0.2. However, a detailed grid of meteorological data is needed to predict the modified temperature-vegetation dryness index; therefore, large-scale use is presently difficult. A new satellite-based aridity index using day/night land-surface temperature differences has been introduced and tested to represent the modified temperature-vegetation dryness index. The satellite-based aridity index was 0.03 when the modified temperature-vegetation dryness index was 0.8, which is the threshold for dust emissions. The relationship between coverage of satellite-based aridity index values greater than 0.03 in the target area (35°N–45°N and 100°E–115°E) and Asian dust events over Japan was analyzed for 2000–2011. Results indicated that coverage of satellite-based aridity-index values greater than 0.03 significantly affects Asian dust events over Japan (R2 = 0.4117, p < 0.05).

Natural and anthropogenic influences on heavy metals in airborne particles over the Korean Peninsula.

Six monitoring stations were selected to characterize the variations in airborne concentrations of heavy metals in South Korea between 1999 and 2012. Three stations represented higher concentrations, and three represented lower concentrations. The heavy metals monitored at these stations include cadmium, chromium, copper, iron (Fe), lead, manganese (Mn), and nickel. During the study period, concentrations of heavy metals at many stations, including those around the Seoul metropolitan area, showed a decreasing trend. However, concentrations of Mn and Fe that are primarily of crustal origin increased at four of the six stations. Some stations were significantly affected by emissions from the local industrial complex (IC), and heavy metal concentrations at those stations were relatively high even in summer. Many heavy metal concentrations were higher in spring than in winter, but wintertime concentrations of Cr and Pb were higher at the stations representing lower concentrations due to the dominant influence of combustion emissions. At stations less affected by emissions from the IC, concentrations of Fe and Mn that are predominantly crustal in origin were higher in spring, when Asian dust (AD) events are most frequent. Although Mn concentrations were also high at stations within the steelmaking IC during AD periods, they were much higher during non-AD periods due to local emissions. Variations in heavy metal concentrations, which are heavily influenced by emissions from the IC, warrant individual analysis because their emission characteristics differ from those of typical cases.

Ammonium deficiency caused by heterogeneous reactions during a super Asian dust episode

AbstractMineral dust particles exert profound impacts on air quality, visibility, and ocean biogeochemistry. Interactions between dust particles and other anthropogenic pollutants modify not only the size spectrum and morphology but also physicochemical properties of dust particles, thereby affecting their radiative properties and ability to act as cloud condensation nuclei and in turn their impact on climate. Here we report field observations on the surface chemical transformations in a super Asian dust plume captured in coastal areas of China and the adjacent marginal seas. The dust plume showed enhanced concentrations of sulfate, nitrate, and calcium along with a decrease in ammonium. The percentages of total Ca in water‐soluble form increased from an intrinsic value of ~5% to 25–40% at four stations along the path of the dust plume. From these increases, we estimated the extent to which carbonate was modified by heterogeneous reactions and calculated that the enhanced sulfate and nitrate could account for 40–60% of the observed concentrations. Our observation suggests that the formation of ammonium sulfate via the H2SO4‐NH3‐H2O ternary system was impeded by heterogeneous reactions in the marine boundary layer when dust loads exceeded a certain threshold. A conceptual model is proposed to elucidate the heterogeneous reactions during the super Asian dust event and their impacts on atmospheric chemistry.

부산지역 PM10과 PM2.5중의 금속 농도와 이온농도 특성

Abstract This study analyzes the chemical composition of metallic elements and water-soluble ions in PM 10 and PM 2.5. PM 10 and PM 2.5 concentrations in Busan during 2010-2012 were 97.2±67.5 and 67.5±32.8 ㎍ / ㎥ , respectively, and the mean PM 2.5 /PM 10 concentration ratio was 0.73. The contribution rate of water-soluble ions to PM 10 ranged from 29.0% to 58.6%(a mean of 38.6%) and that to PM 2.5 ranged from 33.9% to 58.4%(a mean of 43.1%). The contribution rate of sea salt to PM 10 was 13.9% for 2011 and 9.7% for 2012, while that to PM 2.5 was 17.4% for 2011 and 10.1% for 2012. PM 10 concentration during Asian dust events was 334.3 ㎍ / ㎥ and 113.3 ㎍ / ㎥ during non-Asian dust events, and the PM 10 concentration ratio of Asian Dust/Non Asian dust was 2.95. On the other hand, the PM 2.5 concentration in Asian dust was 157.4 ㎍ / ㎥ and 83.2 ㎍ / ㎥ in Non Asian dust, and the PM 2.5 concentration ratio of Asian Dust/Non Asian dust was 1.89, which was lower than that of PM 10 . Key words :PM

Seasonal characteristics of aerosol optical properties at the SKYNET Hefei site (31.90°N, 117.17°E) from 2007 to 2013

AbstractSeasonal characteristics of aerosol optical properties in Sky Radiometer Network (SKYNET) Hefei site are studied using a sky radiometer from March 2007 to May 2013. The aerosol optical depth (AOD), Angstrom exponent (AE), volume size distributions, single‐scattering albedo (SSA), refractive index, and asymmetry factor (ASY) of aerosols are simultaneously retrieved using the SKYRAD.pack version 4.2 software. During the study period, the AOD varied seasonally, with the maximum value of 1.02 ± 0.42 at 500 nm occurring in the summer, and the highest AOD (1.13 ± 0.42) occurred in June due to stagnant climate conditions and accumulation of polluted aerosols before the East Asian summer monsoon. The variation in AE showed a different pattern, with the minimum (0.97 ± 0.28) and maximum values (1.30 ± 0.22) occurring during the spring and fall seasons, respectively. The relatively low value of AE in spring is related to the emission of Asian dust events. The aerosol volume size distributions can be expressed by the trimodal patterns for each season, consisting of a fine mode with R &lt; 0.6 µm, a coarse mode with R &gt; 2.5 µm, and a middle mode located between them. The real part of the refractive index increased with wavelength (380–870 nm) while the imaginary part of the refractive index decreased for all seasons except for the summer. The seasonal mean values of SSA were 0.97 ± 0.02 (summer), 0.95 ± 0.03 (spring), 0.93 ± 0.04 (autumn), and 0.91 ± 0.04 (winter) at 380 nm indicating more absorbing aerosol in the autumn and winter months. Furthermore, aerosol properties were greatly modified by condensation growth as evidenced by the positive dependencies of AOD, SSA, and ASY on relative humidity.

Variations in the structure of airborne bacterial communities in a downwind area during an Asian dust (Kosa) event

Asian dust (Kosa) events transport airborne microorganisms that significantly impact biological ecosystems, human health, and ice-cloud formation in downwind areas. However, the composition and population dynamics of airborne bacteria have rarely been investigated in downwind areas during Kosa events. In this study, air samplings were sequentially performed at the top of a 10-m high building within the Kosa event arrival area (Kanazawa City, Japan) from May 1 to May 7, 2011, during a Kosa event. The particle concentrations of bacterial cells and mineral particles were ten-fold higher during the Kosa event than on non-Kosa event days. A 16S ribosomal DNA clone library prepared from the air samples primarily contained sequences from three phyla: Cyanobacteria, Firmicutes, and Alphaproteobacteria. The clones from Cyanobacteria were mainly from a marine type of Synechococcus species that was dominant during the first phase of the Kosa event and was continuously detected throughout the Kosa event. The clones from Alphaproteobacteria were mainly detected at the initial and final periods of the Kosa event, and phylogenetic analysis showed that their sequences clustered with those from a marine bacterial clade (the SAR clade) and Sphingomonas spp. During the middle of the Kosa event, the Firmicutes species Bacillus subtilis and Bacillus pumilus were predominant; these species are known to be predominant in the atmosphere above the Chinese desert, which is the source of the dust during Kosa events. The clones obtained after the Kosa event had finished were mainly from Bacillus megaterium, which is thought to originate from local terrestrial areas. Our results suggest that airborne bacterial communities at the ground level in areas affected by Kosa events change their species compositions during a Kosa event toward those containing terrestrial and pelagic bacteria transported from the Sea of Japan and the continental area of China by the Kosa event.