Sedimentology and sedimentary geochemistry of aerosol over Ahvaz metropolis

Dust storms are dispersion of very fine solid particles in the air that lead to serious socio-environmental and economic problems. They have been widely observed in recent years in the sky of western and southern parts of Iran. The concentrations of dusts have sometimes reached up to a level estimated 66 times more than the acceptable and normal limits. In order to evaluate textural properties¡ mineralogical and chemical composition of dust samples were collected during dust storms that blew over Ahvaz metropolis in July and August 2014. The results indicated that statistical parameters of the samples were .10 phi¡ 2.17¡ .14 and 0.71 for mean grain size¡ standard deviation¡ skewness and kurtosis respectively. The main mineralogical constituents were quartz¡ feldspar¡ calcite and gypsum with a minor proportion of pyroxene¡ goethite¡ hornblende and biotite. The results also revealed that the shape of sand grains is well-rounded as a result of transportation and abrasion of these grains over a long distance. Moreover¡ XRD analyses of samples reflected the clay minerals fraction of dusts mainly comprised of kaolinite¡ polygorskite and chlorite. These types of clay minerals show a dry climate and an alkaline source area. Atomic absorption and X-ray fluorescence analysis showed major elements as Si¡ Al and Fe with minor elements such as Mg¡ Na and Ca. These dusts also contained minor and toxic elements such as heavy metals¡ and estimated enrichment factors showed that Ni¡ Co¡ Cd and Zn had high enrichment suggesting anthropogenic origin.