Spatio-temporal occurrences and mineralogical–geochemical characteristics of airborne dusts in Khuzestan Province (southwestern Iran) A. Zarasvandi a, ⁎, E.J.M. Carranza b , F. Moore c , F. Rastmanesh a a Department of Geology, Shahid Chamran University, Ahvaz, Iran b Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, The Netherlands c Department of Earth Sciences, Shiraz University, Shiraz, Iran abstract article info Article history: Received 9 September 2010 Accepted 7 April 2011 Available online 14 April 2011 Keywords: Airborne dust Transport Enrichment factor Geological source Khuzestan (Iran) 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 b 10, are of natural origin, whereas Na, Ni, Co, Ba and Cr, with EF N 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. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Dust storms have become a major environmental concern during the last decades in the oil- and gas-rich Khuzestan province in southwestern Iran (Fig. 1). Dust storms frequently occur in Khuzestan mainly during summer, and intense dust storms are particularly associated with easterly-blowing winds (IRIMO Ahvaz, 2008). From March 2007 to June 2009, an average of 60 dust storm days per year has occurred in various cities of Khuzestan province (Zarasvandi, 2009). More than half of the number of dust storm days in 2007–2009 had maximum visibility of b 1 km (IRIMO Ahvaz, 2008). Dust storms in Khuzestan likely emerge from sandy deserts, dried lakebeds, or chemically- and naturally-polluted regions in neighboring countries, are borne upwards and carried by winds to Iran (Zarasvandi, 2009). For example, airborne dusts travel daily eastward from Saudi Arabian and Iraqi deserts to southwestern and southern Iran (Raespour, 2008). The geological and geochemical characteristics of airborne dusts in several countries worldwide have been studied and documented (e.g., Goldstein et al., 2008; Guerzoni et al., 1997; Hirose and Sugimura, 1984; Hladil et al., 2008, 2010; Simonson, 1995; Talbot et al., 1986). However, there are no published studies about the geochemical characteristics, geology and potential impact of airborne dusts on human health in Iran. In this paper, we give an overview of the spatio- temporal occurrences and geological–geochemical characteristics of airborne dusts in Khuzestan. In addition, we explore with the limited data the possibility that occurrence of airborne dusts is associated with worsening prevalence of respiratory diseases in the province (Zarasvandi, 2009). 2. Study area The province of Khuzestan, which occupies an area of 63,213 km 2 in southwestern Iran, has ca. 4 million inhabitants. It is located between Journal of Geochemical Exploration 111 (2011) 138–151 ⁎ Corresponding author. Fax: + 98 611 3331059. E-mail address: zarasvandi_a@scu.ac.ir (A. Zarasvandi). 0375-6742/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2011.04.004 Contents lists available at ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/jgeoexp