عنوان مقاله [English]
The occurrence of drought in the Sistan region and the drying up of the Hamon Lake, as well as the 120-day winds, have created suitable conditions for wind erosion and caused a lot of damage to the natural and human life of the region. These factors have caused the movement of loose sand in the region at a high speed and the sand dunes to expand a lot. Field studies indicate that during frequent droughts in the Sistan region, the movement of sand dunes has been so great that it has caused the burial of a large number of rural houses and the loss of agricultural land, which has led to the migration of the natives of the region in recent years. has followed The dangers caused by the displacement of sand dunes at the level of villages include threats to the health of residents, burial of villages, destruction of soil and public infrastructure, etc. Several factors such as strong and permanent winds, the low slope and low complexity of the plain, the fineness of the soil, successive droughts and the lack of vegetation play a role in the amount of sand movement in the Sistan plain. The aim of this study is to investigate the changes in the sand dunes of Sistan plain by using time series mineralogy and using Landsat satellite data and to propose some solutions to reduce the movement of sand dunes and in turn, reduce its destructive effects on the lives of the residents of the area. The research was conducted using Landsat satellite images with resolution of 30 meters from 1997 to 2020 to investigate the changes of sand dunes in the Sistan plain. According to the results, the extent of sand dunes in August increased from 8.23% in 1997 to 11% in 2020, and in July from 8.83% to 12.9% of the total area of the studied basin, which is almost the trend. It shows a significant increase. Also, the changes in the area of Hamon Lake from 1997 to 2020 show that the lake's water volume has decreased greatly, and this indicates that the expansion of sand dunes in different years is directly related to the changes in the lake level in different times, and the reason for the displacement of sand dunes is the erosive winds of the region. Which have a north to northwest direction with an angle of 330 to 360 degrees (the 120-day wind of Sistan) and the most important facies of harvesting are the saline and puffy areas of the Hamun lake bed and the northern plains.On a global scale, the occurrence of storms and floods are among the most destructive natural hazards (Vesterb and et all, 2022), as most accidents are caused by these two hazards (Yakshin and et all, 2022). Hazards mean natural events that potentially cause danger to humans and what is valuable to them. Hazard has the potential to cause damage, for human health, human, economic, educational activity, damage to property, damage to the environment, loss of flora and fauna, pollution and insecurity of natural disasters are dangerous (Rahimi Harabadi, 2019). The active and dynamic nature of the sand dunes causes the movement of sands towards the settlements to be more frequent and creates many dangers such as threats to the health of residents, burial of villages, destruction of soil and public facilities, and causes financial losses, migration of residents, and finally, a human disaster. (Jadidoleslami, 2019). Therefore, in order to plan fundamentally to solve the problem, it is necessary to analyze the origin of the sands, the role of the morphometric parameters of the sand dunes in the extent of their displacement, and considering the fact that the area is residential, the risks of the sands are identified and solutions are provided to reduce the risks. Sand dunes in the realm of the wind process are considered to be one of the most dynamic geomorphic phenomena on the earth's surface, which are affected by the characteristics of wind speed, direction and frequency on the one hand, and on the other hand by the characteristics of the earth's surface and sedimentary materials (Abbasnejad and Zahab Nouri, 2013). The results of studies on a scale of 1:250,000 show that the sand dunes of Iran include 11 sand seas and 39 hill fields that cover approximately 1.1 million hectares (Abbasi et al., 2019). Sandstorms are one of the most important weather phenomena that spread in many deserts and dry areas of the world, and in recent years, they have received a lot of attention, and every year these incidents cause a lot of damage and casualties in all parts of the world.In order to carry out this research, first, with direct field observations and field operations, to determine the harvesting areas, sampling was done from the transport areas and possible harvesting areas, and based on the mineralogical characteristics and the examination of the genetic relationship of the samples, the primary origin of the sediments was investigated. In order to identify the harvesting areas, sampling was done from the place of accumulation of sands, from different points of possible harvesting areas, and the genetic relationship (similar properties) of the three areas (harvesting, transportation and sedimentation) was investigated through the physical and chemical analysis of the sediments. Took Also, four synoptic stations (Zabol-Zahak-Hirmand-Hamon) were also studied.According to the presented results, the level of heavy metals in the air of Enqelab Street is not hazardous to the health of the residents. Therefore, there is no need to spend enormous expenses in this area. Nevertheless, the health of permanent and temporary residents is threatened by chromium and arsenic due to their high rate of carcinogenesis. The outcome of these investigations indicates that despite recording few different values in some places, the air pollution levels are equal in whole the area, from Enqelab Square to Imam Hossein Square. However, the air pollution level of ValiasCr rossroads is relatively considerable. This difference only has resulted from high volume of traffic in the crossroads. Unfortunately, traffic of students in this area is so heavy that solving Valiasr Crossroad’s traffic issues are considered as an important priority.