Spatio-temporal occurrences and mineralogical–geochemical characteristics of airborne dusts in Khuzestan Province (southwestern Iran)

Abstract Dust storms in Khuzestan province (Iran) are causing problems in industries and human health. To mitigate the impact of those phenomena, it is vital to know the physical and chemical characteristics of airborne dusts. In this paper, we give an overview of the spatio-temporal occurrences and geochemical characteristics of airborne dusts in Khuzestan. Meteorological data from 10 stations in Khuzestan during 1996–2009 indicate (a) an average of 47 dust storm days per year, (b) a lowest annual average of 13 dust storm days in 1998, (c) a highest annual average of 104 dust storm days in 2008, and (d) an average increase of two dust storm days per year. Above-average number of dust storm days usually occurred in the cities of Dezful, Ahvaz, Masjed-e-Soleiman, Abadan and Bostan, whereas below-average number of dust storm days usually occurred in the cities of Mahshahr, Ramhormoz, Behbahan, Shoushtar and Izeh. XRD analyses of airborne dust samples collected in 2008 and 2009 show that the mineralogy of airborne dusts is dominated by calcite, followed by quartz and then kaolinite, with minor gypsum. SEM analyses of the samples indicate that airborne dusts have rounded irregular, prismatic and rhombic shapes. The sizes of airborne dusts vary from 2 to 52 μm, but 10 to 22 μm are the dominant sizes. The smallest and largest dust particles are clays, sulfates or carbonates. XRF and ICP analyses of the samples show that the most important oxide compositions of airborne dusts are SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO and MgO. Estimates of enrichment factors ( EF ) for all studied elements show that Mn, Hf, U, Sc, K, V and Sr, with EF EF  > 10, are of anthropogenic origin. Flat REE patterns with depletion in Th, V, Nb, Zr and enrichment in Al, Rb, Sr and Mn indicate that airborne dusts in Khuzestan come from the same source, which is likely an eroded sedimentary environment outside Iran. In general, airborne dusts in Khuzestan are geochemically similar to airborne dusts elsewhere in the world.

[1]  J. Neff,et al.  Compositional trends in aeolian dust along a transect across the southwestern United States , 2008 .

[2]  S. Taylor,et al.  The geochemical evolution of the continental crust , 1995 .

[3]  R. Chester,et al.  Saharan dust inputs to the western Mediterranean Sea: depositional patterns, geochemistry and sedimentological implications , 1997 .

[4]  T. Yao,et al.  Geochemistry of dust aerosol over the Eastern Pamirs , 2009 .

[5]  M. Alavi,et al.  Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution , 2004 .

[6]  Yanhong Chen,et al.  Enrichment of desert soil elements in Takla Makan dust aerosol , 2002 .

[7]  L. Gomes,et al.  A comparison of characteristics of aerosol from dust storms in central Asia with soil-derived dust from other regions , 1993 .

[8]  Jimin Sun.  Source Regions and Formation of the Loess Sediments on the High Mountain Regions of Northwestern China , 2002, Quaternary Research.

[9]  K. Kreutz,et al.  Major element, rare earth element, and sulfur isotopic composition of a high‐elevation firn core: Sources and transport of mineral dust in central Asia , 2000 .

[10]  E. McDonald,et al.  Characterizing Mineral Dusts and Other Aerosols from the Middle East—Part 1: Ambient Sampling , 2009 .

[11]  Xiaoping Yang,et al.  Rare earth elements of aeolian deposits in Northern China and their implications for determining the provenance of dust storms in Beijing , 2007 .

[12]  D. I. Sebacher,et al.  Distribution and geochemistry of aerosols in the tropical north Atlantic troposphere: Relationship to Saharan dust , 1986 .

[13]  Shi-chang Kang,et al.  Elemental composition of aerosol in the Nam Co region, Tibetan Plateau, during summer monsoon season , 2007 .

[14]  R. Godoi,et al.  Elemental and Single Particle Aerosol Characterisation at a Background Station in Kazakhstan , 2004 .

[15]  S. Galí,et al.  Atmospheric inorganic aerosol of a non-industrial city in the centre of an industrial region of the North of Spain, and its possible influence on the climate on a regional scale , 2009 .

[16]  Onn Crouvi,et al.  Active sand seas and the formation of desert loess , 2010 .

[17]  Jimin Sun,et al.  Changes in Sand Content of Loess Deposits along a North–South Transect of the Chinese Loess Plateau and the Implications for Desert Variations , 1999, Quaternary Research.

[18]  K. Condie.  Another look at rare earth elements in shales , 1991 .

[19]  Cong-Qiang Liu,et al.  A geochemical study of loess and desert sand in northern China: implications for continental crust weathering and composition , 1993 .

[20]  Y. Sugimura,et al.  Excess228Th in the airborne dust: an indicator of continental dust from the East Asian deserts , 1984 .

[21]  O. Bábek,et al.  Dust – A geology-orientated attempt to reappraise the natural components, amounts, inputs to sediment, and importance for correlation purposes , 2010 .

[22]  N. Grevesse,et al.  Abundances of the elements: Meteoritic and solar , 1989 .

[23]  Dongfang Wang,et al.  Characterization of soil dust aerosol in China and its transport and distribution during 2001 ACE‐Asia: 1. Network observations , 2003 .

[24]  S. Gallet,et al.  Geochemical characterization of the Luochuan loess-paleosol sequence, China, and paleoclimatic implications , 1996 .

[25]  R. Simonson.  Airborne dust and its significance to soils , 1995 .

[26]  E. McDonald,et al.  Characterizing Mineral Dusts and Other Aerosols from the Middle East—Part 2: Grab Samples and Re-Suspensions , 2009 .

[27]  D. Morata,et al.  Characterisation of aerosol from Santiago, Chile: an integrated PIXE–SEM–EDX study , 2008 .