mozhgan nosrati

Sand dunes are one of the complications of hot and dry regions, which are associated with many risks, including the creation of dust centers and the destruction of agricultural lands and human constructions. Among the sand dunes that have played an important role in the human activities nearby is the sand dunes of Khuzestan in the southwest of the country. Considering the importance of the subject, in this research, the condition of sand in Khuzestan and the risks caused by it have been investigated. In this research, Google Earth images, Landsat 9 satellite images, MODIS satellite images, as well as digital layers of information are used as the most important research data. The most important research tools include Google Earth, Google Earth Engine and ArcGIS. In this research, firstly, the range of Khuzestan's reservoirs has been drawn and then its changes have been analyzed. In the following, using the AOD index and MODIS images, the dust concentration map of the region has been prepared and its relationship with the region's sensors and human activity has been evaluated and analyzed. The results of this research have shown that the sand of Khuzestan has an area of 2602 square kilometers, and under the influence of the speed and direction of the winds in the region, about 43% of it has an active state, and this problem has caused sand piles in some areas. Move towards agricultural lands.

One of the challenges that many societies face is the occurrence of natural hazards. There are different types of natural hazards, and flood is one of the most important natural hazards, which is always associated with a lot of human and financial losses. In fact, floods are considered as one of the most destructive hazards that cause many human and financial losses every year, so that according to the report of the international database of hazards, floods along with earthquakes and droughts, have had the highest human and financial losses. Also, according to the statistics published in 2010, more than 40% of the natural disasters in the world are caused by floods. In recent years, due to the increasing trend of population and increase in human activities and misplaced human interventions in nature, the possibility of flood occurrence has increased and the risks caused by it have intensified. According to geomorphology, hydro climatic, land cover, etc., different areas have different potentials in terms of flood risk occurrence. Among the regions that have a high potential against flood risk are the southeastern regions of the country. These areas have a high potential against flood risk due to torrential rains, being located at high altitudes and low slopes, as well as poor vegetation, and this issue has caused many floods to occur in recent years. Let's be in this area. Considering the importance of the issue and the occurrence of floods in Esfand 1402 in this region, in this research, the identification of flooded areas and also the analysis of factors affecting its occurrence have been done.

In this research, Sentinel 1 and 2 radar images, Landsat 9 images, and a digital model at a height of 30 meters have been used as the most important research data. The most important research tools are the Google Earth Engine system (to prepare maps of flooded areas and land cover maps) and ArcGIS (to prepare the desired maps). Also, in this research, fuzzy logic model has been used to identify vulnerable areas against flood risk. According to the topic and objectives, this research has been done in several stages. In the first stage, using radar images before the flood and images after the flood, a map of the flooded areas has been prepared. In the second stage, the role of natural factors (elevation, slope, distance from the river, and ranking of the river and land cover) in the flood has been analyzed. In the third stage, based on the results obtained from the previous stages and according to the extent of the flooded areas in different floors, various parameters have been valued and standardized, and finally, by combining the desired parameters based on the fuzzy gamma operator, a map of the damage areas is created. It has been prepared against flood risk.

In this research, the Google Earth Engine system was used to identify the flooded areas in the study area. After preparing the desired images and also applying filters and specifying the threshold limit in Google Earth Engine system, a map of the flooded areas in the southeast of Sistan and Baluchistan province was prepared in March 1402. According to the prepared map, a large part of the southeastern counties of Sistan and Baluchistan province have faced floods, but Dashtiari county and especially its southeastern regions along the Pakistan border have faced the highest amount of flooding. After Dashtiari city, Chabahar city has faced the highest amount of flooding. The analysis of the effective factors in the floods has shown that the height, slope and type of land cover have the highest influence because in a general trend, with the decrease in height, decrease in slope and also decrease in vegetation density, the extent of flooded areas increased.

The results of the identification of flooded areas using radar images have shown that in March 1402, a large part of the region, especially the south-eastern areas of Dashtiari city, faced the risk of flooding. The results of the analysis of the effective factors in the floods have shown that a large part of the flooded areas were related to low altitude and low slope areas, which indicates the direct role of altitude and slope in the floods of the region. Also, the areas that were in the category of desert and barren lands in terms of land cover also had the highest percentage of flooding, so the type of land cover was also one of the effective factors. But the interesting point is that there was no strong relationship between the parameters of the distance from the river and the ranking of the river with the floods that occurred. That is, some areas that were far from the main rivers also faced floods, the main reason of which was the morphological condition of the rivers in the region. According to the mentioned cases, among the effective factors, the height and slope have the highest influence and the distance from the river has the least influence (among the studied parameters). Also, in this research, based on the condition of flood-affected areas and the influence of parameters, vulnerable areas against flood risk have been identified. Based on the results, the southern regions of the study area, including the middle and southern parts of Dashtiari city, the eastern and southern regions of Chabahar city, as well as the southern regions of Konarak city, have the highest flood potential.

Sandwich polyoxometalate of [(FeW9O34)2FeIII4(H2O)2]10- (Fe2W18Fe4) was placed into the gallery of Tris(hydroxymethyl)aminomethane modified layered double hydroxide, Tirs-LDH by a simple one-step process based on the anion-exchange method. The structure of Tris-LDH-Fe2W18Fe4 nanocomposite was characterized and studied by FT-IR, XRD, SEM, EDAX and zeta potential analyses. The results confirmed the successful preparation of the nanocomposite. The catalytic activity of the nanocomposite was investigated in the degradation synthetic dyes of MB, MO, congo red and RB. The parameters like as H2O2 values, pH, amount of catalyst, amount of dye, concentration and as well as its catalytic selectivity were investigated. The results showed that the catalytic activity of Tirs-LDH well enhanced by the intercalation of Fe2W18Fe4. Low cost and available precursor, easy preparation, high adsorption, and fast removal of dye make this work outstanding.

Subsidence risk, unlike many risks such as floods and earthquakes, is insignificant and in the long run causes a lot of damage such as cracking of buildings, sloping of high facilities, destruction of agricultural lands, subsidence, etc. So the areas at risk are facing a lot of challenges. Among the areas that are at risk of subsidence are the plains of arid and semi-arid regions, including the plains of Iran. In fact, the location of a large part of Iran in the arid and semi-arid region has caused these areas to face a shortage of surface water resources, and this has led to overuse of groundwater resources in recent years and the occurrence of the risk has subsided. One of the areas that is at risk of subsidence is Kaboudar Ahang-Famenin plain in Hamadan province. Due to the lack of limiting geomorphological barriers, this plain has been associated with the development of many agricultural lands and due to the lack of sufficient surface water resources, the utilization of groundwater resources in this plain has been more than allowed and this has caused a decline. Extreme groundwater resources in this area and eventually the risk of subsidence. Due to the importance of the issue, in this study, the subsidence of Kaboudar Ahang-Famenin plain has been evaluated and the effective factors in its occurrence have been analyzed.

In this study, in accordance with the subject and objectives, statistical information (information about 13 piezometric wells in the study area), library and video (radar images related to Sentinel 1 satellite, Landsat satellite images and also 30 m high digital model SRTM) has been used as research data. The tools used in the research include GMT software (to prepare subsidence mapping using radar interference and Russian SBAS time series method), Google Earth (to monitor area and identify subsidence) and ArcGIS (to prepare final maps). According to the objectives, this research has been done in three stages. In the first stage, using the digital model of 30 m altitude SRTM and Landsat satellite images, the geomorphological status and land use of the region have been studied. In the second stage, in the second stage, using information related to 13 piezometric wells, the groundwater depletion situation of the region was investigated and in the third stage, using Sentinel 1 radar images and SBAS time series method, the amount was evaluated. Subsidence of Kaboudar Ahang-Famenin plain has been studied.

The study of the altitude situation of the region shows that there is a very small difference in height between the cities of Kaboudar Ahang and Famenin and also there are no significant obstacles and landforms in this distance. Also, the study of the slope classes of the region shows that the area of Kaboudar Ahang-Famenin plain is less than 10% in the slope class and the region does not have steep and restrictive areas. According to the prepared maps, Kaboudar Ahang-Famenin plain, in terms of geomorphology, has no limiting obstacles for the development of agricultural lands as well as residential areas. In fact, the lack of restrictive barriers has led to the development of agricultural lands in this region, especially irrigated agricultural lands in recent years, and this has led to excessive pressure on groundwater resources in recent years. The results of the study of the decline in groundwater resources in the region indicate that the rate of decline in water levels during a period of 24 years has been between 14.7 (Hemehkasi well) to 78.1 (Einabad well) meters. Also, according to the calculations, most of the studied wells have faced an average of more than 2 meters of water level drop annually. Also, the results of the assessment of subsidence in the region indicate that the study area has had a subsidence of 29 to 216 mm during a period of 5 years (from 16/01/2015 to 14/01/2020).

The results of studying the natural state of Kaboudar Ahang-Famenin plain have shown that this plain has a high subsidence potential due to its geomorphological and hydro-climatic conditions. In fact, in terms of geomorphological status, this plain is without limiting obstacles for the development of agricultural lands, and this issue has led to the development of irrigated agricultural lands regardless of environmental capabilities, including the hydro-climatic situation of the region. According to the above cases, the development of agricultural lands, regardless of the capacity of water resources in the region, has led to over-harvesting of groundwater resources and as a result, a sharp drop in groundwater levels Based on the results of the evaluation of 13 wells studied, most of the studied wells, with an average annual water level drop of more than 2 meters and this issue has caused the Kaboudar Ahang-Famenin plain during The 5-year period (from 16/01/2015 to 14/01/2020) should have a subsidence of 29 to 216 mm. Also, the results of the study of the spatial distribution of subsidence have shown that the highest amount of subsidence is related to the middle areas of the region and the distance between Kaboudar Ahang and Famenin cities, and considering that in these areas there was the highest level of groundwater loss, Therefore, it can be said that the main cause of subsidence in the region has been a sharp decline in groundwater resources. The sum of the results of this study has shown that Kaboudar Ahang-Famenin plain is in danger of subsidence and this issue has led to the emergence of numerous depressions in this plain which is a serious threat to human facilities and habitat.