Dust storms in China: a case studyof dust storm variationand dust characteristicsQ. Feng K.N. Endo G.D. Cheng
Abstract The paper discusses the nature of duststorms, which have inherent environmental im-plications. The physical, chemical and mineralog-ical properties of dust sediments collected inKashi, Taklimakan desert, Kunlun mountains,Donghuang, Lanzhou, Ningxia, Xian, Inner Mon-golia and Beijing from 1990 to 1994 were studied.The texture of most aeolian deposits ranges fromsilty clay to clay loam with median particlediameters (Mds) generally between 5 and 63 lm;similar to the loess of central China and the silt/fine sand in western and northern China. The dustsediments were characterized by a predominanceof SiO2 and Al2O3 and a high amount of K2O withmolar ratios for SiO2/Al2O3 and K2O/SiO2 from5.17 to 8.43 and 0.009 to 0.0368 respectively. Thetriple peak spectrum is the main form of massconcentration in a clear sky. In a dust storm itshows as a single peak, with quartz, feldspar,chlorite, illite, calcite and dolomite beingthe dominant minerals. The physical, chemical and
mineralogical properties of the present atmosphericdust are similar to those of wind-blown soils inwestern and central China. The results suggest thataeolian deposits and the fine-grained fractions ofdust sediments collected in northern China aremainly soils transported from the arid and semi-aridregions of China and Mongolia by the prevailingwinds.
Resume Larticle discute de la nature des tempetesde poussie`res, aux consequences importantes surlenvironnement. Les caracteristiques physiques,chimiques et mineralogiques des sediments detempetes de poussie`res preleves a` Kashi, dans ledesert de Taklimakan, les montagnes de Kunlun, a`Donghuang, Lanzhou, Ningxia, Xian, en Mongolieinterieure et a` Pekin de 1990 a` 1994 ont ete etu-diees. La texture de la plupart des depots eoliensvarie des argiles silteuses aux limons argileux. Lacourbe granulometrique presente une valeurmediane generalement comprise entre 5 et 63 lmargileux. Les caracteristiques physiques, chimiquesetrises par une predominance de SiO2 et de Al2O3et une forte teneur en K2O avec des rapports SiO2/Al2O3 de 5,17 a` 8,43 et des rapports K2O/SiO2 de0,009 a` 0,0368. Un spectre a` trois pics estcaracteristique dun ciel clair. Dans une tempetede poussie`res le spectre presente un seul pic avecquartz, feldspath, chlorite, illite, calcite et dolomitecomme mineraux preponderants. Les caracteris-tiques physiques, chimiques et mineralogiques dela poussie`re atmospherique sont semblables a`celles des sols souffles par le vent dans la Chine delouest et du centre. Les resultats de letude sug-ge`rent que les depots eoliens et les fractions finesdes sediments preleves dans la Chine du nord sontprincipalement des sols transportes de regionsarides et semi-arides de Chine et Mongolie par lesvents dominants.
Keywords Dust storms Aeolian deposits Loess Silt China
Mots cles Tempetes de poussie`res Depotseoliens Loess Taille de particule Chine
Received: 9 October 2000 / Accepted: 4 September 2001Published online: 18 December 2001 Springer-Verlag 2001
Q. Feng (&) G.D. ChengCold and Arid Regions Environmentaland Engineering Research Institute,Chinese Academy of Sciences,260 West Donggang Road,730000 Lanzhou, China
K.N. EndoDepartment of Geosystem Sciences,College of Humanities and Sciences,Nihon University, 3-25-40, Sakurajosui Setagaya-ku,156-8550 Tokyo, Japan
Present address: Q. FengDepartment of Geosciences System,College of Humanities and Sciences,Nihon University, 3-25-40, Sakurajosui Setagaya-ku156-8550 Tokyo, Japane-mail: email@example.comTel.:+81-03-53768696Fax: +81-03-53768696
DOI 10.1007/s10064-001-0145-y Bull Eng Geol Env (2002) 61:253261 253
storm on 5 May 1993 during the El Nino event of April toDecember of 1993.
Physical characteristics of dust falls
Based on the relationship between the particle size of air-borne dust and vertical distribution, the particle size oftropospheric dust at an attitude of 6 to 10 km ranged from1 to 100 lm and was characterised by a predominance ofairborne particles with a diameter of 1 to 50 lm (Table 2).On the other hand, the stratospheric aerosol particles witha diameter of 10 km. Consequently, it was considered that the clayey tosilt fractions of the dust sediments accumulated in Chinaare mainly associated with aerosols that have moved in thetroposphere. The dust sediments also contained varyingamounts of sand fraction (14 to 65%). The dust samplesfrom Kashi and Lanzhou in particular had a wide range ofparticle sizes (Table 2). Most of the coarser fraction inthese dust sediments is associated with soil materials blownby the wind from adjacent environments. Table 2 showsthat the particle size of the main dust sediments rangesfrom 5 to 63 lm. The sample from the Taklimakan area waspoorly sorted with a median particle size (Mds) of 2 to200 lm, while the samples from the eastern areas weremoderately well sorted with an Mds of 0.2 to 100 lm (Zhuand Cheng 1994). The sample from Xian was obtained nearthe loess plateau and had an Mds of between 0.2 and 80 lm,somewhat smaller than the samples of loess from theplateau with an Mds ranging from 3 to 16 lm (Table 2).The grain size of the aerosol particles collected from a325 m tower in Beijing was generally less than 0.4 lm, butduring periods of dust storms the dominant grain size wasbetween 0.6 and 1 lm (Qian et al. 1995) while the Mds ofthe well-sorted aerosol material collected on the flat roof ofthe building (about 10 m high) was 3.9 lm (Table 2). Pye(1987) notes that the further the distance from the source,the smaller the value of the Mds of the soils and aerosols.The results of the study are in agreement with other workon the relationships between the diameter of aerosol par-ticles and the transport distance from their source(Middleton et al. 1986; Prospero et al. 1987). However, theparticle size distribution (Mds) and soil texture of the air
fall material may be influenced by the longitude, latitudeand altitude of the sampling site and probably the seasonand meteorological conditions in China, as discussedbelow.
Chemical characteristics of dust
Table 3 presents the chemical components of the dust fallsstudied. As can be seen in the table, the material is char-acterised by a predominance of SiO2 and Al2O3. The SiO2/Al2O3 molar ratios of the dust and loess were 5.17 to 8.43and 6.3 to 9.3 respectively (Table 3). The amount of K2O inthe dust was low (0.57 to 2.07%), being very similar to thatof the loess (1.43 to 3.09%). As seen from Table 3, the K2O/SiO2 molar (0.009 to 0.0368) was also very close to that ofthe loess and aeolian soils of China (0.013 to 0.04). Theseresults suggest that the aerosols and dust collected inChina are predominantly composed of fine soil particlestransported from the loess plateau, the Gobi desert andtheir surrounds.Based on the characteristics of eight chemical componentsof dust in China, two types can be identified. The Xiandust was characterised by a high level of loss on ignitionand CaO, smaller proportions of K2O and greater amountsof Na2O compared with the Beijing type which has lowerlevels of loss on ignition and CaO (Table 3).The suspended matter in the air is composed of two parts:natural material including volcanic particles, salt from thesea and aeolian particles; and material originating fromindustry. The value of the relative concentration of acertain element X to ferrum metal (EFx) is a useful indexfor an analysis of the sources of suspended matter:
EFxX=Feair=X=Fecrust 1where Fe is the ferrum metal; [(X/Fe) air] represents therelative concentration of certain elements (X) to Fe in theair; and [(X/Fe) crust] represents the relative concentra-tion of certain elements (X) to Fe in the crust. The criticalconcentration of certain elements (X) to Fe in the crust hasbeen taken from Liu (1985).The values of EFx for some areas of China are given inTable 4. This shows that the variations in the EFx of most
Table 2Particle size distributions for dust falls in China in 1994. Mds Median particle diameters; So sorting coefficient of sample; Sk standard deviation;Kur kurtosis
Location Variations in Mds Mean Mds So Sk Kur(lm) (lm)
Kashi 0.2200 23.21 1.27 0.756 3.802Kunlun mountains 180 23.13 1.17 1.319 5.557Taklimakan desert (Luntai) 2200 93.54 1.43 0.117 2.316Donghuang 250 17.49 0.52 2.398 7.963Lanzhou 0.3100 17.12 1.55 0.397 3.960Xian 0.280 20.00 0.85 0.966 4.480Ningxia (Yinchuan) 0.480 20.73 1.81 0.291 1.898Inner Mongolia (Xilin Hot) 0.380 10.15 1.08 1.031 2.878B