Document Type : Research Paper

Authors

• Fatemrh Dargahian ¹
• Azadeh Gohardoust ²
• Sakineh Lotfinasabasl ³
• Sara Teimouri ⁴

¹ Associate Professor, Research institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

² Researcher, Desert research division, Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.

³ Assistant Professor, Research institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Iran

⁴ Assistant Professor, Poplar and fast growing trees Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Terhran, Iran.

Abstract

Background and objectives
Many studies have examined the role of neighbouring countries in dust generation in southwestern Iran (Khuzestan) on a case-by-case basis, but which country among the neighbouring countries and in which parts of the same country has the greatest influence on dust generation in the southwest? Iran has not been investigated. In this study, after determining the occurrence of dust using the AOD index and tracing its path through the HYSPLIT model, the main sources of dust emissions affecting the southwest of Iran were identified.
 
Methodology 
To identify foreign areas effective in dust emission in Khuzestan province from 2003 to 2017, one day before the dust phenomenon was reported, the day of dust occurrence, and one day after, on Modis images, by selecting the appropriate algorithm of occurrence. The dust was detected. Three conditions were applied to each dust event: spatial extent in more than 50 % of the synoptic stations of the study area, horizontal field of view of less than 5 km, and detection of the event in more than three consecutive synoptic reports. According to the research, dust ingress into Iran generally occurs in the lower and middle layers of the atmosphere, so the path of dust ingress was investigated at three altitudes of 500, 1000, and 1500 meters. In the HYSPLIT model images, the output of the HYSPLIT method on the day of the event was used together with the AOD image of the day before the dust event in Khuzestan for all days and years. In this way, the areas that had the most dust emission towards Khuzestan were identified and the areas that had at least 30 times by checking the AOD concentration in the days before the occurrence of dust, were identified as areas and centers of dust formation or intensification and emission were identified and its results were zoned for each year and finally the entire period. The share of the most important areas affecting Khuzestan dust was determined in order of priority.
 
Results
Examining the output of all the studied dust events showed that during different years, different regions had the largest share in dust emission to Khuzestan; In 2003, the north and east of Arabia had the most dust emissions towards Khuzestan, and in the same way in the following years, in 2004, the border between Iraq and Syria, in 2005, Saudi Arabia, in 2006, south of Iraq, in 2007, south and southeastern Iraq, in 2008, southern and southeastern Iraq, in 2009, southwestern Iraq, northern Iraq, northern and eastern Arabia, in 2010, southern and southwestern Iraq, in 2011, western Iraq, southern Iraq , North and East Arabia, in 2012, South and Southwest Iraq, in 2013, South and Southwest Iraq, in 2014, North and East Arabia, in 2015 North and East Arabia, in 2016 Iraq-Syria border , western Iraq and southern Iraq, in 2017, the border between Iraq and Syria. During the studied period from 2003 to 2017, the largest share in dust emission; Eastern Iraq was the border between Iraq and Syria, southern Iraq, northern and eastern Arabia

Conclusion 
With 68.8%, Iraq has the largest share in dust emissions entering Khuzestan province, and Saudi Arabia, Syria and Kuwait are in the next ranks, respectively. Due to the upcoming climate changes as well as the redoubled efforts of the upstream countries, Iraq will become a huge source of dust through the construction of earthen dams. The dust produced in this country due to being in the path of synoptic systems towards Iran has had many environmental effects in recent years, especially in the deterioration of Zagros forests. Identifying the areas that emit the most dust helps planners and decision makers to adopt appropriate and efficient diplomacy in controlling and reducing the effects of regional fine dust.

Keywords

• Neighboring countries, Origin of dust
• Modis images, HYSPLIT model, Tracking