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Atmospheric Environment 44 (2010) 2401e2414

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Atmospheric Environment

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Provenances of atmospheric dust over Korea from SreNd isotopesand rare earth elements in early 2006

Min Kyung Lee a, Yong Il Lee a,*, Hi-Il Yi b

a School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, Republic of KoreabKorea Ocean Research Development Institute, Ansan, P.O. Box 29, Ansan 425-600, Republic of Korea

a r t i c l e i n f o

Article history:Received 28 July 2009Received in revised form30 March 2010Accepted 5 April 2010

Keywords:Asian dustHwangsaBackward trajectorySreNd isotopesREEProvenance

* Corresponding author. Tel.: þ82 2 880 6736; fax:E-mail address: lee2602@plaza.snu.ac.kr (Y.I. Lee).

1352-2310/$ e see front matter � 2010 Elsevier Ltd.doi:10.1016/j.atmosenv.2010.04.010

a b s t r a c t

Sr and Nd isotopic composition of pre- and syn-Asian dust (Hwangsa) particles collected from threedifferent water depths at two different offshore sites, western Korea and rare earth elemental compositionof syn-Asian dust particles collected from three islands around the Korean Peninsula in late April 2006were analyzed to interpret their provenance. The dust SreNd isotopic compositions vary spatiotemporally,but they show specific values when the Hwangsa event occurred. Satellite images, airmass backwardtrajectory modeling, and comparison with SreNd isotopic ratios and rare earth elements compositions ofsoils and desert sands of northern China all suggest the major source of dust particles for the late April2006 Hwangsa event to be the Mu Us Desert in northern China. Dust particles of the pre-Hwangsa periodinclude both background dusts and the previous Hwangsa event dust particles, and they are interpreted tohave been originated fromvarious arid regions of China such as the HobqDesert, theMuUs Desert, and theTaklamakan Desert in different times. Different background dust sources during pre-Hwangsa period inearly 2006 resulted from the changing route of the westerlies.

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1. Introduction

The Asian dust (Yellow dust) is called Hwangsa in Korea and isgeneratedwhen surface soils in the arid and semiarid regions of thecentral Asia are lifted by high-speed surface winds and propelledeastward by the prevailing westerlies to Korea. Large quantitiesof mineral dusts generated in arid regions of North China and insouthern Mongolia have been carried over large areas of East Asiaincluding China, Korea, and Japan and even across the Pacific Oceanto North America nearly every spring (Sassen, 2002). The Hwangsaphenomenon generally has been observed 3e5 times in Koreaduring the spring season (Ministry of Environment of Korea, 1999)with the maximum frequency in April. However, the frequency andmagnitude of dust events giving rise to Asian dust aerosols havebeen increased rapidly in the East Asian region from 1999 to 2004(Kurosaki and Mikami, 2003; Lim and Chun, 2006) and so on. Kimet al. (2003) proposed that most dust fallout in Korea originates inarid and semiarid North China and Mongolia.

Hwangsa is generally known to originate from the TaklamakanDesert, the Gobi Desert, the Loess Plateau, and the Erdos Desert whichinclude Mu Us and Hobq Deserts (Fig. 1). Among these arid regions,

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theMongolian Gobi Desert, the Taklamakan Desert, and the high dustemission areas in northern China (containing the Badain Jaran Desert,the Tengger Desert, and the Alashan Desert) are considered to be themajor sources for Asian dust (Zhang et al., 2003b).

Dusts have a diameter ranging from 0.1 mm to about 1000 mm.Large particles with a diameter greater than 30 mm settle downnear the source region, while relatively smaller particles havea lifetime of several days to weeks in the air and can be transportedup to several thousand kilometers (Zhang and Carmichael, 1999).The particles having a diameter of 1e16 mmwith an average of 4 mmare known to be long-range transported aerosols over Korea, Japan,and sometimes even over the Pacific Ocean (Hanna et al., 1999).

There have been many researches regarding the Asian dustevents. In addition tomodeling and climatological studies (e.g., Xuanet al., 2004; Laurent et al., 2006; Zhang et al., 2008), satellite imagingand calculation of backward trajectories have been used to tracethe dusts back to their source areas. Geochemical tracers such as rareearth element (REE) concentrations and SreNd isotopic composi-tions have been also used for this purpose (e.g., Biscaye et al., 1997;Nakano et al., 2004). In general, SreNd geochemistry has been usedto trace the origin and provenance of geologicmaterials (Biscaye andDasch, 1971; Grousset et al., 1988; Nakano et al., 2004; Chen et al.,2007) because minerals and rocks have distinct 87Sr/86Sr and143Nd/144Nd ratios depending on their geological derivation. Theseisotopic ratios are less altered than other indicators like elemental

Fig. 1. Map showing arid regions of Central and East Asia (modified from Nakano et al., 2004). Sampling site of the studied seawater samples is marked by a filled star and Asian dustsamples by three open stars (A: Baekryeong Island; B: Ulleung Island; C: Jeju Island). The deserts of Northern China are as follows: 1) Badain Jaran Desert, 2) Tengger Desert,3) Alashan Desert, 4) Hobq Desert, and 5) Mu Us Desert.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142402

compositions, during transport in the atmosphere and/or afterdeposition as sediments (Goldstein et al., 1984; Grousset et al., 1988;Bory et al., 2002; Grousset and Biscaye, 2005), although change of Srisotopic ratio may occur during chemical weathering (Rao et al.,2006, 2008). Geochemical studies for dust and source areas areimportant not only for provenance inference of a specific dust event,but also for paleoclimate reconstructions over geologic time (Biscayeet al., 1997; Bory et al., 2002). The relationship between increasedproductivity in oceanic environment and dust event is gettingmuch attention. Depending on the dust source regions, the influenceof mineral aerosol particles to the marine ecosystem may differ dueto the different amount of nutrients and elements contained industs. Thus, dust-provenance study is necessary to estimate theinfluence on the biotic response in the ocean environments.

Inwestern Korea, seven Hwangsa events occurred in early 2006;March 11, March 13e14, March 28, April 8e9, April 18, April 24e25,May 1 (Korea Meteorological Administration). This study dealswith the Hwangsa particles collected in seawater prior to, syn- andpost-the April 23e24 Hwangsa event. Dust particles collected priorto Hwangsa event may contain information about the previousHwangsa events as well as about the background dust during non-Hwangsa period. With geochemical information about the sourceareas from previous studies, the REE concentrations and SreNdisotopic techniques have been applied to dust particles associatedwith the Hwangsa events in early 2006 in Korea to identify theprovenances of dusts. By comparing the provenances of dusts forthe Hwangsa event and for background time, information of thecharacteristics of the Asian dusts as well as their influences onmarine ecosystem can be obtained.

2. Material and methods

The occurrence of the Hwangsa event on April 23 and 24, 2006 inthe Korean Peninsula and its vicinity was confirmed by satelliteimages (from 17:33 on April 23 to 19:00 on April 24). In order to

minimize influences of locally-sourced dust, seawater samples werecollected in theYellow Sea off centralwesternKorea (Fig.1). Seawatersamples were collected at two sites during the pre-Hwangsa (April22), mid-Hwangsa (April 24) and post-Hwangsa (April 26) days nearthe high flood time (12:00e14:00). Seawater was collected 1 L eachfrom threewater depths: sea surface,10 mbelow the sea surface, andjust above sea floor. One site is located at 2.4 km from the seashore(inner site:N36� 470 50.700, E 126� 060 51.000, 30 mdeep), and theothersite is located at 10 km offshore from the inner site (outer site: N 36�

510 30.800, E 126� 000 20.300, 70 m deep).Dust particles were collected by percolating seawater samples

through 0.2 mm nuclearpore polycarbonate membrane, and Srand Nd isotopic ratios were determined using a VG 54-30 thermalionization mass spectrometer at the Korea Basic Science Institutefollowing the method of Cheong and Chang (1997). The 87Sr/86Srratio of NBS 987 and the 143Nd/144Nd ratio of the La Jolla standarddetermined during this study were 0.7102473� 0.000004 and0.511839� 0.000005, respectively. Total procedural blank level wasless than 0.3 ng for Sr and 90 pg for Nd. Neodymium variations areexpressed in the 3Nd notation (Depaolo and Wasserburg, 1976),using a present-day value of CHUR (Chondrite Uniform Reservoir)143Nd/144Nd¼ 0.512638 (Jacobsen and Wasserburg, 1979).

Coeval Hwangsa samples were collected on three islands:Baekryeong (09:40 April 21e09:50 April 25), Ulleung (09:55April 22e08:00 April 25) and Jeju Islands (09:35 April 24e09:35April 25) (Fig. 1) by a high-volume air sampler. These dust sampleswere analyzed for REEs by a PerkineElmer Elan 6100 inductivelycoupled plasma mass spectrometer (ICP-MS), using the methodgiven by Jarvis (1988) at the Korea Basic Science Institute. Analyticalprecision for the REEs is generally better than 5%. US GeologicalSurvey Standard MAG-1 was used for calibration.

Airmass backward trajectory modeling was achieved usinga HYSPLIT4 (Hybrid Single-Particle Lagrangian Integrated Trajec-tory) model provided by Air Resources Laboratory of NationalOceanic and Atmospheric Administration, USA.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e2414 2403

Satellite images were taken by MTSAT (Multifunctional TransportSatellite)andweremodified for illustrating theamountofdustby Infra-Red Difference Dust Index (IDDI) by Korea Meteorological Adminis-tration. IDDI is a semi-quantitative measure of the concentration ofatmospheric aerosols, which are dominated by mineral dust in desertregions (Brooks and Legrand, 2000; Legrand et al., 1994, 2001).

3. Results

3.1. Backward trajectory results

Airmass backward trajectory was performed for five days prior toeach sampling date. Trajectory of Hwangsawas reconstructed for twoaltitude ranges (<3 kmand>5 km) because aeolian dust sediments inKoreamaybe amixture of the coarse component (median size: 15 mm)which is transported by the winter monsoon surface winds andthe fine component (median size: 3 mm) which is transported by thehigh-altitude westerlies (Sun et al., 2002, 2004). The fine componentrepresents the general background dust load all year round.

Fig. 2 shows that the transport paths of airmass which trans-ported Hwangsa to Korea around noon on April 22, 24, and 26.Fig. 2a (low-altitude route) represents that the airmass moved fromRussia to Korea via Mongolia and China or moved fromMongolia toKorea via China, and it could transport dusts from the MongolianGobi Desert, the Ongin Daga Sandy Land, the Hobq Desert, and theMu Us Desert. The high-altitude transport path (Fig. 2b) representsthat the airmass moved from Russia to Korea via Kazakhstan,Uzbekistan, Mongolia and China or moved from western China toKorea, and it could transport dusts from theMongolian Gobi Desert,the Ongin Daga Sandy Land, the Taklamakan Desert, the QaidamDesert, the Badain Jaran Desert, the Tengger Desert, the Mu UsDesert, and the Hobq Desert.

The HYSPLIT4 is a useful air trajectorymodel, especially for long-range transport of airmass (Draxler and Hess, 1997). The backwardtrajectory results, however, may contain some uncertainties due tothe uncertainty in meteorological data, especially when appliedover periods of several days. To reduce this uncertainty, our studyuses backward trajectories information not as a principal tool but asa supplementary means with satellite images, supporting results ofgeochemical characterization.

3.2. SreNd isotopic ratios of seawater dust particles

Masses of seawater dust particles collected on April 24 and 26were mostly one order of magnitude larger than that of April 22

Fig. 2. Backward trajectory results for Hwangsa collected from the western Korean sea onaltitude. The possible Hwangsa source regions are marked by dotted circles.

(Table 1). The amount of dust particles collected fromsea surface arelarger at outer site than at inner site on April 24 and 26, whereas theamount of dust particles collected from the other depths (below10 m from sea surface and near seafloor) are larger at inner site thanat outer site (Table 1). Analytical results of Sr and Nd isotopic ratiosof dust particles are given in Table 1. 87Sr/86Sr ratios do not varybetween the two sampling sites (0.715e0.722) (Table 1; Fig. 3). 3Ndvalues range from�15.8 to�13.8with a narrower range at the innersite (�15.8 to �14.8) than at the outer site (�15.7 to �13.8) (Fig. 3).

Although 3Nd values and 87Sr/86Sr ratios each overlap to someextent among dust samples with time, 3Nd value tends to decreasegradually and 87Sr/86Sr ratio tends to increase (Fig. 3). Sr and Ndisotopic values are widely scattering on April 22, while both valuesof April 24 and 26 are clustered in a narrow field. The magnitude ofscattered degree among the samples is as follows: April 22[April24>April 26. Especially, the samples collected from the sea surfaceshow a large difference between the inner and outer sites on April22, while the samples of April 24 and 26 collected from the samewater depths show a slight difference between the two sites.

3.3. REE compositions

Chondrite-normalized REE patterns of dust samples collectedfrom Baekryeong, Ulleung, and Jeju Islands are indistinguishablefrom each other despite different concentrations by an order ofmagnitude between samples of Jeju and Ulleung islands (Table 2;Fig. 4a). They have significant negative Eu anomalies (Eu/Eu*¼ 0.55� 0.02). Total REE content of three samples showsvariation ranging from 1.4 to 14.7 ppm, much lower than those ofchondrite (2599 ppm) and Post-Archean Australian shale (PAAS)(183 ppm), probably resulting from their higher quartz content thanthe latters. The (La/Yb)n ratios are similar in all samples rangingfrom 11.26 to 11.68, with an average of 11.48, greater than those ofchondrite (1.48) and PAAS (9.08).

4. Discussion

4.1. Factors affecting the Sr isotopic composition

According to previous investigations on the NdeSr isotopiccompositions of Chinese deserts and loess (Liu et al., 1994; Biscayeet al., 1997; Nakano et al., 2004; Rao et al., 2006, 2008; Chen et al.,2007), Nd isotopic compositions of the desert sand and eoliandeposits have little fractionation during the processes of weath-ering, transport and deposition, suggesting that Nd isotopic

April 22 (red line), 24 (blue line) and 26 (green line) for a) low-altitude and b) high-

Table 1Sr and Nd isotopic ratios and 3Nd values of dust particles collected from seawater.

Sample Position Mass (g) 87Sr/86Sr 2s SE 143Nd/144Nd 2s SE 3Nd

April 22, 20060422-1-1 aInner Sea surface 0.0029 0.715 0.000013 0.511867 0.000046 �15.0320422-1-2 10 m below 0.0017 0.719 0.000014 0.511845 0.000016 �15.4750422-1-3 Near sea floor 0.0063 0.717 0.000034 0.511854 0.000020 �15.3030422-2-1 bOuter Sea surface 0.0025 0.719 0.000013 0.511928 0.000085 �13.8420422-2-2 10 m below 0.0064 0.717 0.000027 0.511875 0.000043 �14.8820422-2-3 Near sea floor 0.0024 0.715 0.000011 0.511913 0.000068 �14.137

April 24, 20060424-1-1 Inner Sea surface 0.0104 0.721 0.000011 0.511875 0.000053 �14.8800424-1-2 10 m below 0.0103 0.720 0.000011 0.511841 0.000012 �15.5390424-1-3 Near sea floor 0.0127 0.721 0.000011 0.511881 0.000012 �14.7670424-2-1 Outer Sea surface 0.0211 0.718 0.000020 0.511861 0.000055 �15.1630424-2-2 10 m below 0.0077 0.719 0.000014 0.511888 0.000013 �14.6400424-2-3 Near sea floor 0.0058 0.722 0.000011 0.511866 0.000012 �15.067

April 26, 20060426-1-1 Inner Sea surface 0.0152 0.721 0.000013 0.511865 0.000010 �15.0750426-1-2 10 m below 0.0121 0.721 0.000011 0.511881 0.000013 �14.7690426-1-3 Near sea floor 0.0127 0.721 0.000013 0.511830 0.000048 �15.7640426-2-1 Outer Sea surface 0.0160 0.721 0.000014 0.511858 0.000055 �15.2130426-2-2 10 m below 0.0098 0.721 0.000013 0.511831 0.000057 �15.7360426-2-3 Near sea floor 0.0088 0.721 0.000011 0.511847 0.000045 �15.432

a Inner site : N 36 47 50.7, E 126 06 71.0.b Outer site : N 36 51 30.8, E 126 00 20.3.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142404

composition can be used as a robust provenance indicator.However, Sr isotopic composition is strongly affected by theseprocesses, and thus Sr isotopic composition can be used as a prov-enance monitor only when the samples are carefully pretreated,e.g., selecting suitable grain-size fractions to eliminate the influ-ence of mineral sorting and using the silicate fraction throughweak-acid leaching for excluding the influence of carbonatemineral formed during weathering and/or pedogenesis. In ourseawater dust samples, the range of grain size is supposed to be notlarge because these wind-blown dusts have already been sortedduring the long-range transport. However, carbonate was notpretreated when Sr isotopic composition was analyzed.

Fig. 3. 3Nd values and 87Sr/86Sr ratios of the bulk dust particles collected from seawatersamples atdifferentwaterdepths at two sample locationsonApril 22, 24 and26, 2006.Opensymbol represents inner site samples, and filled symbol represents outer site samples.

In addition to carbonate dust, planktonic organisms suchas foraminifera and coccolith are possible candidates which havepotential to affect the Sr isotopic composition of the studied dustsamples in seawater. According to Cheng and Cheng (1963), theYellow Sea region is a rather closed area where planktonic fora-minifera are very rare to absent. Cheong (1995) also reported theabsence of planktonic foraminifera near the study area. In case ofcoccoliths, Gephyrocapsa oceanica is known to be dominant in theYellow Sea (Okada and Honjo, 1975), but it has not been reportedin the study area (cf., Cheong, 1995). Accordingly, the possiblecontamination of skeletal carbonates in the studied seawatersamples may not be notable for consideration. Considering thatsignificant negative Eu anomalies of dust samples collected onthree islands reflect low plagioclase contents, the widely scatteredSr isotopic values of seawater dust particles, especially those ofApril 22, could be ascribed to carbonate dusts derived from varioussource regions.

4.2. Provenance of dusts during pre-Hwangsa periodand Hwangsa event

SreNd isotopic ratios of dusts which were transported to Koreaon April 22, 24, and 26 vary in time, space, and water depth.Although location and water depth where seawater was collecteddid not influence much on the isotopic ratios in the dust samples ofApril 24 and 26, dust particles collected from seawater on April 22plotted somewhat scattered (Fig. 3). This result indicates that dustsof April 22 were not sourced from same regions which wereresponsible for the Hwangsa on April 23 and 24. Similar Sr and Ndisotopic compositions of dusts of April 24 and 26 are interpreted tobe the results of residence effect.

To compare SreNd isotopic compositions of Hwangsa particlescollected from seawater samples with those of possible sourceareas, we compared our results with previous research results.Table 3 represents the compiled analytical data of soil and sandsamples with their locations. Sr and Nd isotopic data of twelveregions of northern China are from the Gurbantunggut Desert, theOngin Daga Sandy Land, the Horqin Sandy Land, the TaklamakanDesert, the Qaidam Desert, the Badain Jaran Desert, the Tengger

Table 2Rare earth element concentrations of dust samples from Baekryeong (BC), Ulleung (UC) and Jeju (JC) islands (in ppb).

Sample ID Mass (g) La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Eu/Eu* (La/Yb)nP

REE

BC283 0.0347 583.66 1174.15 127.19 683.88 90.99 18.57 107.75 13.05 77.29 13.44 38.56 5.22 33.73 4.95 0.57 11.68 2972.41UC332 0.0108 275.28 575.28 63.64 337.39 45.41 8.52 52.71 6.63 35.40 6.68 18.95 0.00 16.15 0.00 0.53 11.50 1442.04JC298 0.2503 2715.1 5999.7 643.5 3352.4 448.5 86.1 530.1 66.1 355.2 66.6 189.4 25.3 162.7 23.9 0.54 11.26 14664.57

Eu/Eu*¼ Eun/[(Smn)(Gdn)1/2] (Taylor and McLennan, 1985). Subscript n means normalization against chondrite.

Fig.4.a)

Chondrite-normalized

REEplots

ofHwangsa

collectedfrom

threeislands.b)

Chondrite-normalized

REEplots

ofHwangsa

fine-grainedsilicate

fractionsofthe

desertsand

andloess

which

showssim

ilarREE

distributionpattern.c)

Chondrite-normalized

REEplots

ofHwangsa

fine-grainedsilicate

fractionsofthe

desertsand

andloess

which

showsdifferentREE

distributionpattern.See

Table4for

datasource

ofdesertsandsand

loesses.

Table 3Sr and Nd isotopic ratios and 3Nd values of loesses and desert sands in northern and western China.

No. Sample name Latitude Longitude Sample type (mm) 87Sr/86Sr 143Nd/144Nd 3Nd

Gurbantunggut DesertJunggar Basin (Honda et al., 2004)1 9217 Loess 0.712 0.512 -6.32 9329-1 Loess 0.711 0.512 �5.5

Gurbantunggut Desert (Chen et al., 2007)3 G-10 45.06 87.46 Sand (<75) 0.712 0.513 �1.24 G-13 45.51 88.28 Sand (<75) 0.712 0.513 �1.6

Sand (<5) 0.717 0.512 �4.05 G-16 45.60 89.11 Sand (<75) 0.714 0.512 �3.3

Ongin Daga Sandy LandOngin Daga Sandy land (Chen et al., 2007)6 BT-15 43.69 111.95 Sand (<75) 0.711 0.512 �6.37 BT-28 42.75 115.90 Sand (<75) 0.713 0.512 �5.9

Sand (<5) 0.717 0.512 �6.78 BT-31 43.42 116.10 Sand (<75) 0.711 0.512 �4.49 BT-56 42.15 116.83 Sand (<75) 0.711 0.512 �7.0

Horqin Sandy LandNaiman (Honda et al., 2004)10 201 Loess 0.711 0.512 �6.611 204 Loess 0.710 0.512 �5.612 213 Sand 0.715 0.513 �1.5

Horqin Sandy Land (Chen et al., 2007)13 BT-46 43.30 121.45 Sand (<75) 0.712 0.512 �5.614 BT-48 43.27 121.18 Sand (<75) 0.713 0.512 �6.8

Sand (<5) 0.717 0.512 �6.715 BT-50 43.05 120.81 Sand (<75) 0.713 0.512 �5.3

Gobi DesertGobi desert (Nakano et al., 2004)18 Dzamin Uudo 43.43 111.54 Sand 0.715 0.512 �4.919 Erenhot 43.70 112.00 Sand 0.714 0.512 �5.320 Siziwang qi 41.80 111.80 Sand 0.716 0.512 �9.921 Huade 42.80 114.50 Loess 0.713 0.512 �7.622 Bayan Mod 41.50 105.00 Loess 0.716 0.512 �9.223 Baotou 40.70 110.00 Sand 0.712 0.512 �21.124 Urad Qianqi 40.43 108.40 Loess 0.717 0.512 �20.7

Taklamakan DesertTaklamakan desert (Nakano et al., 2004)25 45 38.00 83.00 Sand 0.716 0.511985 �12.726 46 40.00 94.80 Sand 0.715 0.511928 �13.927 47 38.00 77.50 Sand 0.710 0.512150 �9.528 48 37.50 81.00 Sand 0.710 0.512119 �10.1

Taklamakan Desert (Honda et al., 2004)29 2811 Sand 0.715 0.512 �10.9

Sand (<45) 0.713 0.512 �10.930 3003 Sand 0.717 0.512 �11.9

Sand (<45) 0.713 0.512 �10.0Taklamakan Desert (Honda et al., 2004)31 931023$6-b Sand 0.716 0.512 �11.0

Sand (<45) 0.715 0.512 �10.432 901018 Sand 0.714 0.512 �9.7

Sand (<45) 0.713 0.512 �9.933 H91801 Sand 0.721 0.512 �12.034 KA92302B Sand 0.713 0.512 �9.9

Taklamakan Desert (Chen et al., 2007)35 TK-02 40.43 84.25 Sand (<75) 0.716 .512078 �10.9

Sand (<5) 0.727 .512111 �10.336 TK-03 40.02 84.29 Sand (<75) 0.714 .512078 �10.937 TK-06 38.85 83.50 Sand (<75) 0.714 .512150 �9.538 TK-08 38.04 83.06 Sand (<75) 0.716 .512105 �10.439 TK-11 36.41 81.84 Sand (<75) 0.715 .512129 �9.940 TK-12 36.42 81.96 Sand (<75) 0.716 .512082 �10.841 AKS-03 39.69 94.35 Sand (<75) 0.717 .512037 �11.7

Sand (<5) 0.730 .512090 �10.7

Qaidam DesertQaidam desert (Chen et al., 2007)42 CD-1 36.98 95.34 Sand (<75) 0.717 .512101 �10.543 CD-2 37.12 94.45 Sand (<75) 0.719 .512125 �10.0

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142406

Table 3 (continued)

No. Sample name Latitude Longitude Sample type (mm) 87Sr/86Sr 143Nd/144Nd 3Nd

44 CD-4 37.48 94.03 Sand (<75) 0.717 .512127 �10.045 CD-5 37.99 93.75 Sand (<75) 0.718 .512116 �10.246 ZZH-02 36.68 93.79 Sand (<5) 0.727 .512156 �9.447 NMH-02 36.38 96.42 Sand (<5) 0.733 .512171 �9.148 DLHD-03 36.80 97.69 Sand (<5) 0.731 .512113 �10.2

Badain Jaran DesertBadain Jaran Desert (Nakano et al., 2004)49 Badain Jaran Shamo 39.00 102.50 Sand 0.715 0.512165 �28.750 Badain Jaran Shamo 38.34 102.54 Sand 0.715 0.512165 �12.8

Badain Jaran Desert (Chen et al., 2007)51 BJ-04 39.77 102.47 Sand (<75) 0.717 0.512 �9.852 BJ-05 41.95 102.25 Sand (<75) 0.713 0.512 �7.453 BJ-06 42.02 101.58 Sand (<75) 0.717 0.512 �10.254 BJ-07 41.23 100.97 Sand (<75) 0.714 0.512 �8.355 BJ-08 41.08 101.50 Sand (<75) 0.717 0.512 �9.956 BJ-09 40.93 100.63 Sand (<75) 0.716 0.512 �8.457 Surf-43 39.53 105.50 Sand (<75) 0.716 0.512 �9.458 Surf-49 39.73 103.23 Sand (<75) 0.716 0.512 �9.259 Surf-51 39.40 102.55 Sand (<75) 0.717 0.512 �9.660 BDJL-01 39.60 100.74 Sand (<75) 0.718 0.512 �10.9

Sand (<5) 0.729 0.512 �8.3

Tengger DesertTengger Desert (Nakano et al., 2004)61 Tengger Shamo 38.50 105.00 0.722 0.512021 �12.062 Tengger Shamo 38.50 105.00 0.719 0.512072 �11.063 Jinchang 38.35 102.33 Loess 0.721 0.512016 �12.1

Tengger Desert (Chen et al., 2007)64 TGL-10N 37.45 105.50 Sand (<75) 0.718 0.512 �10.665 TGL-13N 37.68 104.97 Sand (<75) 0.719 0.512 �11.766 TGL-16N 37.93 104.35 Sand (<75) 0.719 0.512 �10.4

Sand (<5) 0.72767 MQ-01 38.64 103.11 Sand (<75) 0.721 0.512 �11.7

Sand (<5) 0.732 0.512 �12.0

Mu Us DesertMu Us Desert (Nakano et al., 2004)68 Mu Us Shamo 38.50 108.50 0.718 0.512102 �10.569 Wuhai, Mu Us Shamo 39.15 107.56 Loess 0.717 0.512 �15.970 Erdos 40.00 110.00 Sand 0.721 0.511918 �14.071 Erdos 40.00 110.00 Sand 0.736 0.511370 �24.7

Ordos Desert (Honda et al., 2004)72 China 1 Sand 0.716 0.512 �12.773 China 2 Loess 0.726 0.512 �14.174 China 3 Sand 0.716 0.512 �19.775 China 4 Loess 0.715 0.512 �12.576 881026 Sand 0.716 0.512 �11.7

Mu Us Desert (Chen et al., 2007)77 Surf-06 38.22 109.53 Sand (<75) 0.717 0.512 �14.078 Surf-07 38.72 109.68 Sand (<75) 0.715 0.512 �16.479 Surf-08 39.13 109.78 Sand (<75) 0.716 0.512 �17.280 Surf-11 38.77 108.55 Sand (<75) 0.716 0.512 �13.481 Surf-12 39.05 108.08 Sand (<75) 0.717 0.512 �15.082 Surf-14 39.65 108.58 Sand (<75) 0.715 0.512 �12.183 Surf-15 39.92 109.05 Sand (<75) 0.716 0.512 �16.384 Surf-21 40.18 111.35 Sand (<75) 0.717 .512016 �12.185 Surf-24 40.33 110.35 Sand (<75) 0.719 .511843 �15.5

Mu Us Desert (Rao et al., 2008) Sand (<5) 0.721 .511732 �17.786 1 38.27 109.53 Sand (<75 mm) 0.717 0.511920 �14.087 2 38.72 109.68 Sand (<75 mm) 0.715 0.512 �16.488 3 39.13 109.78 Sand (<75 mm) 0.716 0.512 �17.289 4 38.77 108.55 Sand (<75 mm) 0.716 0.512 �13.490 5 39.05 108.08 Sand (<75 mm) 0.717 0.512 �15.0

Hobq DesertHobq Desert (Chen et al., 2007)91 Surf-26 40.47 109.70 Sand (<75 mm) 0.717 0.512 �14.392 Surf-29 40.08 109.35 Sand (<75 mm) 0.717 0.512 �13.4

Sand (<5 mm) 0.723 0.512 �12.093 Surf-33 40.42 108.62 Sand (<75 mm) 0.717 0.512 �11.8

(continued on next page)

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e2414 2407

Table 3 (continued)

No. Sample name Latitude Longitude Sample type (mm) 87Sr/86Sr 143Nd/144Nd 3Nd

94 Surf-34 41.45 108.65 Sand (<75 mm) 0.716 0.512 �13.1Sand (<5 mm) 0.724 0.512 �11.5

95 Surf-39 40.24 107.02 Sand (<75 mm) 0.717 0.512 �12.096 Surf-40 40.05 106.77 Sand (<75 mm) 0.719 0.512 �14.2

Sand (<5 mm) 0.722 0.512 �14.9

Hobq DesertHobq Desert (Rao et al., 2008)97 6 39.65 108.58 Sand (<75 mm) 0.715 0.512 �12.198 7 39.92 109.05 Sand (<75 mm) 0.716 0.512 �16.399 8 40.18 111.35 Sand (<75 mm) 0.717 0.512 �12.1

Hobq Desert (Rao et al., 2008)100 9 40.35 110.35 Sand (<75 mm) 0.719 0.512 �15.5101 10 40.47 109.70 Sand (<75 mm) 0.717 0.512 �14.3102 11 40.08 109.35 Sand (<75 mm) 0.717 0.512 �13.4103 12 40.42 108.62 Sand (<75 mm) 0.717 0.512 �11.8104 13 41.45 108.65 Sand (<75 mm) 0.716 0.512 �13.1105 14 40.23 107.02 Sand (<75 mm) 0.717 0.512 �12.0

Alashan (Alxa; Ulan Buh) DesertAlxa Desert (Ulan Buh Desert) (Nakano et al., 2004)106 Alxa (Ulan Buh) 38.60 105.50 Loess 0.718 0.512121 �10.1107 Alxa Zuoqi 40.40 105.38 Loess 0.719 0.512075 �11.0108 Murengaole 38.60 105.50 Loess 0.718 0.512106 �10.4109 Yinchuan 38.30 106.30 Loess 0.719 0.512101 �10.5110 Yinchuan 38.25 105.59 Loess 0.721 0.512081 �10.9111 Zhongwei 37.46 105.53 Loess 0.717 0.512037 �11.7112 Helan Shan 38.21 105.49 Loess 0.719 0.512061 �11.3

Loess PlateauLoess Plateau (Nakano et al., 2004)113 Taiyuan 38.00 112.50 Loess 0.718 0.512 �12.2114 Jiuquan 39.51 97.53 Loess 0.721 0.512 �11.6115 Zhangye 39.14 99.28 Loess 0.722 0.512 �11.2116 Yuhuang 38.16 102.06 Loess 0.723 0.512 �11.8117 Wuwei 37.20 102.54 Loess 0.720 0.512 �11.4118 Lanzhou 36.21 103.33 Loess 0.717 0.512 �10.8119 Lanzhou 36.00 103.80 Loess 0.719 0.512 �11.3120 Xian 34.20 108.80 Loess 0.718 0.512 �9.4

Loess Plateau (Chen et al., 2007)121 HX 36.62 107.32 Loess 0.718 0.512 �9.7122 XF 35.78 107.60 Loess 0.718 0.512 �9.2123 LC 35.85 109.60 Loess 0.718 0.512 �10.0

Loess Plateau (Rao et al., 2008)124 15 36.35 104.62 Paleosol 0.720 0.512 �9.8125 16 35.72 107.72 Paleosol 0.718 0.512 �10.1126 17 35.72 107.72 Loess 0.718 0.512 �9.2127 18 36.62 107.32 Loess 0.718 0.512 �9.7128 19 35.75 109.42 Paleosol 0.718 0.512 �12.2129 20 35.75 109.42 Loess 0.718 0.512 �10.0130 21 34.07 109.00 Paleosol 0.720 0.512 �9.4131 22 37.50 112.50 Loess 0.719 0.512 �12.1132 23 38.50 113.00 Loess 0.719 0.512 �11.6133 24 40.00 113.00 Loess 0.717 0.512 �11.2134 25 40.30 112.10 Loess 0.719 0.512 �11.2135 27 40.57 113.50 Loess 0.714 0.512 �11.6

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142408

Desert, the Mu Us Desert, the Hobq (Qubqi) Desert, the Alashan(Ulan Buh or Alxa) Desert, the Loess Plateau, and the Gobi Desert.Fig. 5 shows the results of this study and previously reported data ofsoils and sands from 135 locations in western and northern China,demonstrating a wide variation in 87Sr/86Sr ratios (0.709905e0.736280) and 3Nd values (�28.66 to �0.8).

REE compositions of dusts collected on Baekryeong, Ulleung,and Jeju Islands show a similar distribution pattern, Eu anomaly,and (La/Yb)n ratios despite different total REE concentrations andsampling time interval (Table 2; Fig. 4). For example, dusts collectedon Jeju Island represent Hwangsa, and those collected on Baek-ryeong and Ulleung islands include Hwangsa as well as pre-

Hwangsa dusts. The similarity of REE distribution patterns amongdust samples suggests that eolian dusts were well homogenizedin terms of REE composition, irrespective of pre-Hwangsa dustmixing. Probably this might have been caused by the large mass ofHwangsa for eolian dusts collected on Baekryeong islands and thusmasking the characteristics of the pre-Hwangsa dusts. The mass ofdust in Ulleung Island is smaller than that of Jeju Island althoughUlleung Island has the largest integrated airflux among threeislands. Therefore, the difference in REE concentration seems to beresulted from the mass of dust collected in each sampling areacaused by the different routes of airmasses which passed over threeislands during the sampling period.

Fig. 5. 87Sr/86Sr versus 3Nd(0) for the Hwangsa and fine-grained silicate fractions of the desert sand and loess. See Table 3 for data source. A dotted rectangle in the upper right is anenlarged area where studied samples plotted.

Table 4Rare earth element concentrations of loesses and desert sands in northern China (in ppm).

Sample La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Eu/Eu* (La/Yb)nP

REE

Loess Plateau (Yokoo et al., 2004)Yinchuan 30.0 62.0 6.7 28.0 5.6 0.9 5.0 0.6 3.4 0.7 2.0 0.3 2.0 0.3 0.5 10.1 147.6Lanzhou 33.0 66.0 7.4 30.0 5.9 1.1 5.5 0.7 3.9 0.8 2.0 0.3 2.3 0.3 0.6 9.7 159.1Xian 36.0 72.0 7.8 32.0 6.2 1.1 6.0 0.7 4.5 0.7 2.3 0.3 2.2 0.3 0.6 11.0 172.1

Hunshandake Desert (Yang et al., 2007)7.1 12.4 1.5 5.6 1.1 0.6 1.2 0.2 1.1 0.2 0.7 0.1 0.6 0.1 1.5 7.4 32.5

Tengger Desert (Yokoo et al., 2004)11.0 21.0 2.5 9.0 1.9 0.5 1.7 0.2 1.2 e 0.6 0.1 0.7 0.1 0.9 10.6 50.5

Hobq Desert (Kwon et al., 2004b)Ordos 1 18.8 34.6 3.9 15.2 2.9 0.8 2.3 0.3 1.7 0.4 1.0 0.2 1.0 0.1 0.9 12.9 83.0Ordos 2 14.9 26.9 3.0 11.5 2.2 0.7 1.7 0.2 1.2 0.2 0.6 0.1 0.6 0.1 1.1 16.7 63.9Ordos 3 19.7 35.6 4.0 15.6 2.9 0.8 2.4 0.3 1.7 0.4 1.0 0.2 1.0 0.2 0.9 13.9 85.7Ordos 4 19.5 36.3 4.0 15.3 2.9 0.8 2.3 0.3 1.7 0.4 1.0 0.2 1.0 0.2 0.9 13.0 85.7Ordos 5 20.1 35.9 4.1 15.8 3.0 0.8 2.4 0.3 1.8 0.4 1.0 0.2 1.0 0.2 0.9 13.5 86.8

Taklamakan Desert (Kwon et al., 2004a)TK1 36.5 68.1 7.1 27.0 5.2 1.2 5.1 0.7 3.9 0.8 2.2 0.3 2.0 0.3 0.7 12.4 160.3TK4 29.0 53.1 5.7 22.0 4.4 1.2 4.3 0.6 3.5 0.7 2.0 0.3 1.8 0.3 0.8 10.6 128.7TK8 25.8 47.3 5.1 19.6 3.8 1.1 3.8 0.5 3.1 0.7 1.7 0.2 1.6 0.2 0.9 10.7 114.6

Alashan Desert (Kwon et al., 2004b)Al1 20.6 38.0 4.4 17.0 3.5 0.8 3.0 0.4 2.3 0.5 1.3 0.2 1.2 0.2 0.7 11.4 93.3Al2 16.4 30.2 3.5 14.2 2.9 0.7 2.5 0.3 1.9 0.4 1.1 0.2 1.0 0.2 0.8 10.9 75.5Al3 14.3 26.7 3.1 12.4 2.6 0.7 2.2 0.3 1.8 0.4 1.0 0.2 1.1 0.2 0.9 8.9 66.9

Mu Us Desert (Honda et al., 2004)China 2 (loess) 24.5 50.8 5.8 21.0 4.1 1.0 3.4 0.5 3.1 0.6 1.8 0.3 1.8 0.3 0.8 9.2 118.9China 1 (sand) 12.6 24.9 3.0 11.0 2.1 0.6 1.8 0.3 1.6 0.3 0.9 0.1 0.9 0.1 1.0 9.2 60.3

Horqin Sandy Land (Honda et al., 2004)9345 (sand) 8.0 14.1 1.8 7.1 1.5 0.4 1.8 0.3 2.1 0.5 1.3 0.2 1.5 0.2 0.8 3.7 41.09333 (loess) 30.1 64.3 7.5 27.5 5.5 1.1 4.7 0.8 4.3 0.9 2.6 0.4 2.6 0.4 0.7 7.8 152.7

Gurbantunggut Desert (Honda et al., 2004)9217 27.4 57.9 6.8 26.4 5.3 1.2 4.8 0.8 4.7 0.9 2.6 0.4 2.6 0.4 0.7 7.2 142.12713389 26.9 56.6 6.8 26.2 5.3 1.2 4.9 0.8 4.6 0.8 2.5 0.4 2.7 0.4 0.7 6.8 140.1

Eu/Eu*¼ Eun/[(Smn)(Gdn)1/2] (Taylor and McLennan, 1985). Subscript n means normalization against chondrite.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e2414 2409

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142410

The REE patterns of Hwangsa particles collected from threeislands were compared with those of their possible source areas, inwestern and northern China (Fig. 4). REE data (Table 4) are from;the Loess Plateau, the Hunshandake Desert, the Tengger Desert, theHobq Desert, the Taklamakan Desert, the Alashan Desert, theMu UsDesert, the Horqin Sandy Land, and the Gurbantunggut Desert.

4.2.1. Hwangsa sources of April 23e24Nd and Sr isotopic compositions of dust particles of April 24 and

26 plot near the field of the Mu Us Desert and the Hobq Desert(Fig. 5). The REE patterns of dust samples collected on three islandsare similar to those of the Gurbantunggut Desert, the Horqin SandyLand, the Mu Us Desert (loess), the Alashan Desert, the TaklamakanDesert, and the Loess Plateau, based on Eu anomaly and (La/Yb)n(Fig. 4b). On the other hand, sands from the Hobq Desert, theTengger Desert, the Mu Us Desert (sand), and the HunshandakeDesert show different REE patterns from the Hwangsa (Fig. 4c).Comparison of REE patterns of dust particles with those of soils anddesert sands of northern China excludes the Hobq Desert from thepossible source area.

After considering the airmass backward trajectory resultsand the satellite images, the dust transported to the Korean sea on12:00 April 24, 2006 is interpreted to have been originated from theMu Us Desert between 09:00 and 21:00 on April 22 (Fig. 6) bythe surface winds. Therefore, the Mu Us Desert in North China isinterpreted to be the main dust source for the Hwangsa event inKorea on 23 and 24 April 2006.

4.2.2. Provenance of dusts before April 23Dust particles of different sampling depths and locations on April

22 might have been delivered by different airmasses due to differentsettling time. The tidal conditions when seawater was sampled werenearly at peak flood tide (j6m) and the wave height was 1e2 m.Therefore, contamination due to riverine input or reworked particlesfrom the sea floor seems not significant for consideration. This inter-pretation is supported by the large difference in 3Nd and Sr isotopiccompositions of sea surface and near sea-floor samples between theinner and outer sites on April 22.

Isotopic compositions of dust particles collected from the seasurface and 10 m below the sea surface plot near the Mu Us Desert

Fig. 6. a) Backward trajectory results for five days from April 24 12:00 for airmasses that passa large amount of dust generated around the Mu Us Desert and adjacent areas around 21:

and the Hobq Desert fields (Fig. 5). Fig. 7a illustrates the backwardtrajectory results for the dust of the sea surface on April 22.After considering the backward trajectory results and the satelliteimages, the dusts transported to the Korean sea surface at 12:00April 22, 2006 are interpreted to have been originated from theHobq Desert between 09:00 and 21:00 on April 21 (Fig. 7) by thehigh-altitude westerlies.

For dust particles collected near sea floor and fromwater depthsbelow 10 m from the sea surface, settling velocity of dust particleswas calculated to infer the timing of dust arrival on the sea surfacebased on the Stoke’s law:

Vs ¼ 118

rs � rfm

gD2

where Vs denotes settling velocity of particle; rs, density of particle(2.65 g cm�3); rf, density of seawater (1.03 g cm�3); m, seawater’sdynamic viscosity (1.384�10�2 g cm�1 s�1); g, gravitational accel-eration (980 cm s�2); D, diameter of particle (4 mm). As a result, Vs iscalculated to be about 3.7 cmh�1 when the seawater temperatureis 10 �C. The time needed for dusts sinking down to 10 m, 30 m, and70 m depths are calculated to be 270 h, 811 h and 1892 h, respec-tively, assuming little turbulence effect. Accordingly, the dusts atthree water depths (10 m, 30 m and 70 m) seemed to have arrivedat the sea surface at 04:00 on April 11, 17:00 onMarch 19 and 16:00on February 2, respectively. However, note that this calculation istoo simplistic without considering advection of seawater due totidal action as well as wave agitation to keep dusts in suspension.In fact, dust particles may remain near the sea surface a little longerbecause tides and waves are able to retard sinking of dust particles.Considering this time lag, the dust particles at 10 m depth couldhave been originated from the preceding Hwangsa event occurredon April 8. Similar isotopic compositions of dust particles at bothinner and outer sites at this depth (below 10 m) compared tothose at other two depths could be resulted from the same dustorigin e the April 8 Hwangsa event. In a similar manner, the dustparticles near sea floor collected from the inner site could havebeen originated from the Hwangsa event occurred on March 14.

The Nd isotopic composition of dust particles collected froma depth 10 m below the sea surface suggests that they were derived

ed four different Hwangsa sampling sites in Korea. (b) IDDI satellite image showing that00 on April 22, 2006.

Fig. 7. a) Backward trajectory results for five days from April 22 12:00 for airmasses that passed seawater sampling site on western Korea sea. b) IDDI satellite image showing thata large amount of dust generated around the Mu Us Desert and adjacent areas around 17:00 on April 21, 2006.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e2414 2411

from the Mu Us Desert and/or the Hobq Desert (Fig. 5). The back-ward trajectory results for the Hwangsa event on April 8 (Fig. 8a)and satellite images (Fig. 8b, c) indicate that dust particles weretransported from the Mu Us and/or the Hobq Desert around 18:00on April 7 by surface winds and/or around 09:00 on April 6 by thewesterlies. Thus, the Hwangsa on April 8 was originated from theMu Us and/or the Hobq Deserts.

Dust particles collected near sea floor at the inner site werederived from theMu Us Desert and/or the Hobq Desert, considering

Fig. 8. a) Backward trajectory results for five days from April 8 16:00 for airmasses that pa large amount of dust generated around the Mu Us Desert and adjacent areas around b) 1

the Nd isotopic composition (Fig. 5). According to the backwardtrajectory results (Fig. 9a) and the satellite image (Fig. 9b), the dustsare interpreted to have been originated from the Hobq Desert near21:00 onMarch 12 by the surfacewinds. Besides, considering largersettling velocity of coarser particles, dust particles of the Hwangsaevent of April 8 could have mixed with the Hobq Desert-origin dustparticles collected from the sea floor. The similar isotopic compo-sition of the dusts at near sea floor depth with that of the Mu UsDesert at inner site supports this interpretation (Figs. 3 and 5).

assed seawater sampling site on western Korea sea. IDDI satellite image showing that8:33 on April 7, 2006 (c) around 10:00 on April 6, 2006.

Fig. 9. a) Backward trajectory results for five days from March 14 21:00 for airmasses that passed seawater sampling site on western Korea sea. b) IDDI satellite image showing thata large amount of dust generated around the Hobq Desert and adjacent areas around 21:33 on March 12, 2006.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e24142412

Fig. 10 illustrates the backward trajectory results for the dustsfromnear sea floor at the outer site on April 22, and the TaklamakanDesert could have provided dusts near 21:00 on January 29 bythe high-altitude westerlies, and dusts reached to the sea surface atthe outer site near 15:00 on January 31. Time lag of about 2 daysbetween January 31 and February 2 is acceptable considering theuncertainty of the calculated result.

Fig. 10. Backward trajectory results for five days from January 31 15:00 fo

In summary, eolian dusts prior to the Hwangsa event of April 23and24, 2006were derived from three different regions ofwestern andnorthern China in different times. Dust particles from the sea surfaceand near sea floor at the outer site represent background dusts orig-inated from the Hobq and Taklamakan Deserts. The high-altitudewesterlies were responsible for these background airborne duststransport. The different provenances of pre-April 23 background dusts

r airmasses that passed seawater sampling site on western Korea sea.

M.K. Lee et al. / Atmospheric Environment 44 (2010) 2401e2414 2413

might have been resulted from the change of high-altitude westerliesroute owing to Rossbywave (westerlies wave). For dusts of the April 8Hwangsa event, the Mu Us and Hobq Deserts were probable sources.The Hobq Desert was a probable source for the dust particles for theMarch 14 Hwangsa event.

4.3. Implication for productivity change in the Yellow Sea

Mineral aerosol particles which are originated from Chineseand Mongolian desert regions are known to play an active role inthe biogeochemical cycles of trace elements in the mid-latitudeNorthern Hemisphere (Okada et al., 1990; Zhang et al., 1997). In theYellow Sea, atmospheric deposition is the most important nutrientcontributor due to the relatively minor contributions of upwellingwaters and riverine inputs (Zou et al., 2000; Chen et al., 2004), andZhang (1994) provided evidence of a correlation between planktonblooms and episodic atmospheric depositions of nutrients andtrace elements. Kai and Huiwang (2007) reported that the YellowSea was the most affected sea by Asian dust during 2000e2002among several seas near China (Bohai Sea, Yellow Sea, East ChinaSea, Korea Strait, East Sea), rendering the Yellow Sea the best areafor studying the effect of the Asian dust on marine ecosystem.

The Yellow Sea is oligotrophic and in many regions, P-limited(Zou et al., 2000). According to the study on the content of availablesoil phosphorous in five climatic zones in China (Zhang et al., 2005),thewarm temperate zone including theMuUs andHobqDeserts hasthe highest soil available phosphorus density (8.9 g/m3), while thetemperate desert zone including the Taklamakan Desert has lowersoil available phosphorus density (6.3 g/m3). Iron is another limitingfactor which stimulates primary productivity in the oceans. Dustaerosol samples collected from the Mu Us Desert contain elementalFe concentration of 12.39� 6.94 mgm�3 (Zhang et al., 2003a), whichis higher than that of the dust aerosols collected from the Takla-makan Desert (6.00�10.85 mgm�3; Makra et al., 2002).

Considering these facts, Hwangsa originated from the Mu UsDesert could provide a larger amount of Fe and phosphorous tothe western Korean sea than that originated from the TaklamakanDesert. Thus, study on the provenance of Asian dust event maycontribute to understanding the role of dusts on synchronouschange of bioproductivity in the sea.

5. Conclusions

Asian dusts falling on Korea during a Hwangsa event in lateApril 2006 were studied using SreNd isotopic compositions of dustparticles collected from seawater samples from the western Koreansea and REE compositions of dust particles collected by a high-volume air sampler on three islands around the Korean Peninsula.The dust isotopic composition showed temporal and spatial varia-tionswithwater depth and/or sampling site, but it is nearly identicalin samples of the syn- and immediate post-April 23e24 Hwangsaevent. Comparison of SreNd isotopic ratios of dust particles of early2006 with those of soils and desert sands of western and northernChina reveals that the possiblemain source area of dust particleswasthe Mu Us Desert and the Hobq Desert, with minor contributionfrom the Taklamakan Desert. More specifically, dust particles for theApril 23e24 Hwangsa event were derived from the Mu Us Desert,whereas those for the April 8 Hwangsa event from the Mu UsandHobq deserts. Dust particles for theMarch 14Hwangsa event areinterpreted to have been originated from the Hobq Desert. Back-ground dust particles for the non-Hwangsa period in early 2006were originated from the Hobq and Taklamakan Deserts. A combi-nation of SreNd isotopic composition and REE composition ofHwangsa provides a useful tool to study the provenance of aeolian

dusts in association with airmass trajectory technique and satelliteimage observation.

Acknowledgements

This study was supported by a grant from the Korea OceanResearch and Development Institute (PRI 2005e2007) and partlyby a SNU-SEES BK 21 program. Prof. B.C. Cho is thanked for the useof lab facilities. The authors are indebted to Y.W. Lee and T.J. Choifor their assistance in collecting seawater samples. Furthermore,the authors acknowledge the NOAA air resource laboratory forproviding HYSPLIT online. This manuscript has benefited muchfrom constructive comments by two anonymous reviewers and theEditor, Chak K. Chan.

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