Assessment of chemical and mineralogical characteristics of airborne dust in the Sistan region, Iran

Abstract

Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0-5 cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-Ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30-40%), calcite (18-23%), muscovite (10-17%), plagioclase (9-12%), chlorite (~6%) and enstatite (~3%), with minor components of dolomite, microcline, halite and gypsum. X-Ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO 2 , CaO, Al 2 O 3 , Na 2 O, MgO and Fe 2 O 3 , exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EF) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.

Ambient Particulate Matter Concentration Levels and their Origin During Dust Event Episodes in the Eastern Mediterranean

“…For instance, Saharan-and Sahelian-derived eolian dust frequently contains small quantities of chlorite (in our study close to 2.3%) less than kaolinite, whereas in Asia chlorite can be met at higher concentrations than kaolinite, a significant mineral of African dust (Rashki et al 2013). Moreover, albite and palygorskite, which constitute 10.6 and 4.3% of the sample, respectively, do not exist in the list of the first seven abundant minerals in deserts of North China.…”

“…The only exception is the gypsum which has the tendency to dissolve in rain-water samples and remains unaffected in dry sample where shows an abundance of 5% (Table 4). Rain may also be an important factor in altering soil crust compositions (Rashki et al 2013).…”

Identification of sand and dust storm source areas in Iran

“…Being affected by a series of factors including the complete dryness of Hamoun lakes, the reduction in soil moisture and vegetation cover, and the construction of reservoir dams and irrigation projects upstream (Rashki et al, 2013b;Alizadeh-Choobari et al, 2014), Sistan Basin has now become another significant SDS source in West Asia. Because of the intensity, duration, wind speed and altitude of dust storms in Sistan Basin, dust loading from this area might have an important influence on the development of extreme dust storms, especially in the summer (Rashki et al, 2012).…”

“…Ordinary front winds usually have higher speeds but lower tensile strength, while hurricane front winds move upward and through the gap created in the front and crest of the storm drag with more dust upwards (Ekhtesasi and Gohari, 2013). As for dust materials, dust storms in this area mainly consist of large quantities of quartz-rich, feldspar and mica-bearing silt, as well as mafic components from flood basalt sources and carbonate minerals from dolomites (Rashki et al, 2013b).…”

Spatio-temporal variability of dust aerosols over the Sistan region in Iran based on satellite observations

“…The percentage of these diseases increases in summer (June-July) due to frequency and intensity of dust storms. More recently, Rashki et al (2012) studied the sediment loading and particulate matter (PM) concentrations at the Hamoun Basin (north edge of Sistan), Rashki et al (2013a) analyzed the PM concentrations and Air Quality Index (AQI) over Zahedan, south Sistan, while Rashki et al (2013b) and Engelbrecht et al (2009) analyzed the chemical composition of dust over Sistan and surrounding regions in Afghanistan, respectively. However, the above-mentioned studies are of a limited time period and a long-term dust aerosol variability either from ground-based measurements or satellite remote sensing still is lacking.…”