Document Type : Original Article
Department of Environment, Geological Survey of Iran
Department of Environment, Amirkabir University, Tehran, Iran
Department of Geology, Ferdowsi University, Mashhad, Iran
Department of Geology, ETH Zurich, Switzerland
Department of Physical Jeography, Faculty of Geoscience, Shahid Beheshti University, Tehran, Iran
Agricultural and Natural Resources Research, Ahvaz, Iran
Khuzestan Province is one of the regions of Iran which has been most affected by the newfound phenomenon of dust storms due to recent droughts. Dust storms, which in some cases are considerably concentrated and accompanied by a reduction of horizontal view to 20 meters, causes various problems such as harmful effects to human health, absorption or dispersion of sunlight and affecting the region’s temperature, a negative impact on agricultural activities, reduced visibility and road transportation problems and tens of health, environmental and economically undesirable effects. So, due to the importance of the issue, a mineralogical and geochemical study of dust storms has been conducted in order to determine their probable sources, the environmental characterization of existing elements in dust and their role in polluting the environment.
Materials and methods:
In order to conduct dust sampling, a glass table was designed with edges to the height of 5 centimetres and an area of 1.5 square meters. In this matter, from April 2011 studies were conducted for 2 years in Khuzestan Province (Abadan, Ahvaz and Bostan). Through investigating previous studies and extracting the specified focuses, five sources have been identified for dust entering the country. 30 dust samples were collected and analyzed for elemental and mineralogical analysis conducted. The mineralogical analysis was conducted by using powdered samples and a Siemens XRD diffraktometer D5000 ICP-OES JY70 PLUS and an ICP Optical Emission Spectrometer (model Varian 735-ES) were utilized for elemental analysis. All the tests were conducted at the laboratories of the Geological Survey and Mineral Explorations of Iran.
Results and discussion:
According to previous studies, during finding sources through investigation over the period from 2011 to 2012, 50 sources were identified, namely that much of the dust storms which have affected Khuzestan Province during 2011 and 2012 originated from the following regions. Region 1: Northwest Iraq and eastern Syria, both sides of the Euphrates River (with at least 9 cases of dust storms over the 2 years). Region 2: wetlands and dried lands in southern Iraq (Mesopotamia) with at least 5 ases of dust storms in Khuzestan. Region 3: neighbouring and northerly lands of Lake Tharthar in Iraq with 4 cases of dust storms. Region 4: western areas of Iraq (Anbar Province) and eastern Syria (Hamus Province) with 3 cases of dust storm occurrences over two years. Region 5: northern borders of Saudi Arabia and the East of Jordan with 2 cases of dust storms during the period studied. Mineralogical studies of dust in the destination area showed that there are calcite, quartz, clay minerals and an insignificant amount of dolomite, gips and feldspar in the focus areas of regions 1, 3, 4; and halite, dolomite, quartz, and gypsum in the southern focus areas of Iraq (region 2). This, then, associates the sedimentary environment related to erosion and evaporation (dried lakes and wetlands and sediments of old lakes) as the geological source of these particles. Most of the heavy metals and toxic and radioactive elements in the dust are highly enriched. These enrichments are influenced by hydrocarbon materials and upstream processes of the oil industry, contamination caused by repeated wars and use of microbiological and chemical weapons containing radioactive elements, accumulation of clay particles due to the high absorption capacities of some of the heavy metals, drying up of wetlands and land of the source region and creating evaporating conditions, most of which is anthropogenic.
The storms entering Khuzestan Province derive from dried up wetlands and lakes and the sediments of old lakes and high enrichment, creating an unusual level of elements in dust due to the high absorption capacity of the elements into clay particles resulting from hydrocarbon materials. It is also caused by effects of the imposed war on Iran (with Iraq) and the drying of wetlands because of human activities.