مجله مخاطرات محیط طبیعی
پیاپی 27 (بهار 1400)

Soil salinization is one of the dominant processes of land degradation in arid and semi-arid regions.  Soil salinity is one of the most important problems affecting many parts of the world. Salty soils in agricultural areas reduce the annual crop yield of most crops. As a first step, soil sampling and Landsat images are pre-processed. Different salinity indices such as NDSI (normalized salinity index), BI (brightness index) and SI (salinity index) were used to map the salinity of the study area. As well as Laboratory measurements of electrical conductivity (EC) and soil acidity (pH) have also been performed. In this regard, the values of three salinity indices NDSI, BI, SI for 2017, 2015, 2010, 2005, and 2000 were calculated in ENVI and GIS software. Based on the results of satellite imagery analysis, saline soils in the west and southwest of Ilam province (sub-basins of Mehran, Musian-Abdanan, Abbas-west-east and Molab basins) are located. According to field surveys and soil sampling for different areas of Ilam province, it was found that pH values below Mehran basin, south Dehloran and downstream of Simareh Dam are above 8.5 and indicate alkaline and sodium soils. And other examples show unusual, up to slightly salted soil. This means that the results of the remote sensing analyzs partially confirm the data obtained from estimating soil EC and pH values in the study area.

Natural hazards are unfortunate accidents that cause a lot of irreparable damage to the natural environment and man-made phenomena every year. Floods are among the hazards that have always been likely to occur as a natural hazard to humans. In the meantime, identifying flood-prone areas is one of the first measures to deal with them. Darab city was not isolated from this matter and this study was conducted to prepare a flood potential map of the city. Because many criteria are involved in flooding in any region. Therefore in this study 12 criteria including Slope, Aspect, Rainfall, Runoff Height, Curve Number status (CN), Flow Accumulation, Soil Hydrological Groups status, Land Use, Vegetation Density, Drainage Network Density, Basin Elevation, and Distance to Drainage Network, selected and maps were prepared for each. In the next step, the prepared maps were weighted using the Analytic Hierarchy Process (AHP) method and using Expert Choice software and their fuzzy process was performed by the fuzzy logic model. Finally, the overlap of the layers was performed using a fuzzy algebraic summation operator (SUM) in Arcmap software and thus maps related to flood risk zoning of Darab city with different return periods and on 5 floors were extracted. In maps obtained with different return periods, the pattern is almost identical and similar. According to the final plans, the risk of floods with return periods of 25, 15, 5, and 50 years, respectively 9.91, 9.39, 8.4, and 9.93% of the area of the city with flood risk Very low fertility and 9.24, 10.64, 11.90 and 8.65% of its area has a very high risk of flooding.

Today, the world's greatest environmental threat is global warming and climate change. The consequences of climate change are water and food shortages, disease, unemployment and migration, poverty, resource crises and instability. The aim of this study is to zoning the country's regions of Iran based on geopolitical indicators of the effects of climate change. The present study is descriptive-analytical in terms of purpose, application and method. Data collection and documentary and survey information have been done with questionnaire tools. The statistical population of the research is purposeful and includes experts and specialists in the field of climate change working in meteorological organizations, the environment and passive defense. The questionnaire was designed based on the indicators of the effects of climate change and geopolitics and after distribution, 60 questionnaires were collected. Friedman's comparative test then prioritizes the impact of climate change on geopolitics, which are: 1- Poverty and Unemployment, 2- Dryness, 3 - Social security 4 - Production of strategic agricultural and livestock products 5 - Health and public health and 6 - Maintaining the balance of the ecosystem will have the greatest impact on the country's geopolitics. After that, the country's zoning was drawn using GIS software to validate the effects of climate change in the country's regions. According to the research findings, according to the prioritized geopolitical indicators, the effects of climate change in Sistan and Baluchestan, Kohgiluyeh and Boyer-Ahmad provinces, Qom, Bushehr and Alborz will be most affected. For this purpose, the government can use a medium-term and long-term plan to reduce the geopolitical challenges caused by the effects of climate change in these areas. Finally, it is necessary to implement effective methods such as watershed management and use of clean energy to reduce Greenhouse Gases emissions to adapt to the effects of climate change.

In this regard, the present study evaluates the economic damages of dust phenomenon on the agricultural sector of Masjed Soleiman districts and estimates the willingness to pay people to control this phenomenon. The statistical population of the study is the rural households of Masjed Soleiman city in Khuzestan province. Required data were collected through 400 questionnaires through multi-stage sampling. By determining the total sample number, the sample number of each village was determined by proportional allocation based on the population of the selected villages. Also using the Logit model, factors affecting farmers' willingness to pay for crop protection against dust were estimated using Shazam 9 software and mathematical calculations with Maple 18 software. The results showed that in the study area, the variables of age, number of employees, education and income had a positive and significant effect on the willingness of farmers to pay for crop protection against dust. The total value of the damages against dust was obtained for maintenance of agricultural crops 791448408 tomans per year for Masjed Soleiman districts.