Spatio-Temporal, Mineralogy and Micro-Morphology of Dust Occurrences and Centers with Internal Sources in the Khouzestan Province

Extended abstract 1- Introduction Dust occurrences as natural events are common in arid, semi-arid and desert areas. Investigation of the dust with internal sources in the Khuzestan province including about 15 percent of the dust events coming to the region and the presence of the annual average of 50 times of the internal dust (with the concentration maximum of PM10 particles more than 8000ppm in Khuzestan) is very important. Recently, air pollution due to the occurrence of dust is one of the worst environmental problems in the western and southwestern Iran, especially the Khouzestan province. Dust mineralogy is an important factor in source identification of the particles. In this way, frequency, distribution, mineralogy and morphology of the internal dust and so the depositional centers susceptible to dust production in this province were studied for the first time. The source, generation, transport and sediment of dust have been paid significant attention by the scientific community. Investigations of dust events are important because of the impact of the dust on the environment, particularly on the health and human biological system. The regional dust had negative effects on the health of human life which can cause asthma, bronchitis and lung diseases due to their carrying micro-organisms. Dust causes severe soil erosion, desertification, and a significant reduction in the agricultural production and farming as well. Thus, such a crisis is concerned with economic consequences in the short- and long-term periods. In this way, distribution, mineralogy and morphology of the internal dust and so depositional centers susceptible to dust producing in this province were studied for the first time. 2- Methodology At first, the frequency and the spatial-temporal data related to the internal dust (Code 07) over the 2009-2015 periods were investigated using 13 synoptic data stations in Khuzestan. 32 TSP samples of dust and 65 sediment sample were taken. Mineralogical study of the 11 dust samples associated with 11 sediments samples were determined by X-Ray Diffraction (XRD) using Philips 3040 PW at Kansaran Binaloud Company in Pardis Science and Technology Park, Tehran, Iran. With regard to morphology studies, Scanning Electron Microscopy (SEM) was used on 20 internal and external dust samples at the central laboratory of Shahid Chamran University of Ahvaz (LEO 1455 VP). Also, grading analysis of the erosional zones using LPSA method and Q10- Q50- Q90% standards were done on 11 samples at the central laboratory in Shahid Chamran University of Ahvaz, Iran. 3- Results The obtained data shows 406 times internal dust in the studied period. Also, the internal dust has a continuity between 1-3 day(s). Bostan, the northeastern city, with the annual frequency of 78 days, has the maximum, and Izeh and Masjid Suleiman, with the annual mean of 6 days, has the minimum duration of the dust in the province. With regard to time, the year of 2009 and the month of June have experienced the largest amounts of dust. Also, the frequency and duration of the internal-derived dust are compatible with the east-western and north-southern increasing trend. The temperature, height, relative humidity and precipitation indexes do not show the same pattern as the frequency of the internal dust in 2009-June, 2015 period. 4- Discussion & Conclusions Mineralogical study of the 11 dust samples and 11 sediments samples using XRD shows that carbonates, silicates and evaporates are the main mineralogy composition of the internal dust and the erosional sediments in Khuzestan. Halite and dolomite are considered as the main minerals of dust particles, respectively, in over the 70 and 30 percent of the samples, respectively. Evaporate minerals such as gypsum and halite are found more in the internal dust compared with the external dust coming to Khuzestan. Also, quartz frequency in the internal dust occurrences is about 45% more than the dust occurrences from the neighboring country. In addition, minor minerals such as albite are present in all the samples and the other minerals including gypsum, chlorite, illite, and muscovite are the minor minerals in the dust samples as well. SEM analysis shows that spherical and crystalline shapes are the most abundant ones in the dust with calcite, quartz and halite composition. Grading analysis of the erosional zones using LPSA method and Q10- Q50- Q90% standards, illustrates high amounts of silt particles in the Province. But clay distribution was seen in 10-35% of the samples. 15-24 µm is the predominant grading range in Khuzestan. Mean grading of these samples with about 18.9 µm, is a sign of dust-producing potential of all the desert centers in the Khuzestan province.