مجله مدیریت مخاطرات محیطی
سال دهم شماره 4 (زمستان 1402)

The subsidence is one of the hazards that has posed a significant threat to many plains in the country in recent years. Asadabad Plain in Hamedan province is among those plains with a high potential for subsidence due to its hydro climatic conditions and geomorphology. Because of the importance of this issue, in this research the subsidence status of Asadabad Plain has been assessed and unlike many previous researches, the role of human factors in its occurrence has been analyzed. To do so, Sentinel-1 radar images, Landsat 5 and  8 satellite images, statistical information related to piezo metric wells in the region, and digital elevation layers were used as the primary data sources. Using the SBAS time series method, a subsidence map of the area from 2015 to 2022 was generated, followed by an analysis of the impact of groundwater depletion and land-use changes on subsidence. The results indicate subsidence ranging from 132 to 704 millimeters in Asadabad Plain during 2015 to 2022, with the highest subsidence occurring in the central regions of the plain. Considering the significant correlation (a correlation coefficient of 0.709) between subsidence and groundwater level decline, it can be concluded that one of the main causes of subsidence in Asadabad Plain is the depletion of groundwater resources. The assessment of land-use changes also reveals an increasing trend in agricultural land and human-built areas, corresponding to increased exploitation of groundwater resources and intensified land surface pressure, leading to exacerbated subsidence. Given the persistence of subsidence in this plain, remote sensing monitoring and the establishment of fixed GPS measurement stations facilitate monitoring the rate and extent of subsidence.

Floods are considered one of the most important and abundant geomorphic hazards in the country, which cause a lot of damage every year. Aji Chai basin, located in East Azerbaijan province, witnesses devastating floods every year due to its large area and special topographical conditions. Therefore, the main aim of this study is to prepare a flood hazard potential map in this basin. To achieve this aim, 18 parameters effective in the occurrence of this hazard and two statistical methods of frequency ratio (FR) and statistical index (SI) have been used. The investigated parameters were Elevation, Slope, Aspect, Rainfall, Distance to the river, River density, Normalized Difference Vegetation Index, land use, Distance to bridge, Distance to dam, lithology, hydrological soil groups, Topographic wetness index, Sediment transport index, Stream power index, Drainage texture, Geomorphology and earth curvature. The location of the past flood points in the area was used to determine the parameters weight and implement the research models. The final maps were prepared from the product of the weights of each parameter class in their information layers and were classified into five classes using the Natural Breaks tool. Study the final maps showed that hazard zones spatial distribution patterns were similar in both models. In this way, the areas downstream of the basin and around the main streams of the area are the most dangerous zones. The accuracy evaluation of the results of both models with the ROC curve showed that the values of the area under the curve for SI and FR models were 0.945 and 0.919, respectively, which shows the excellent performance of both models in preparing flood hazard maps.

Hazards are multifaceted knowledge that is rooted in humans, human activities and the natural environment and plays a major role in the development of human societies and their protection against disasters. For this reason, as an interdisciplinary knowledge, it has attracted the attention of researchers of various sciences. In this regard, this research tries to use the data available in the Web of Science database and with the help of CiteSpace software to evaluate and analyze the evolution of the concepts related to the knowledge of hazards using the co-citation method. The results of the research show that the concepts of risk, hazard, climate change and vulnerability have the most frequency, the words risk assessment, exposure to risk and management have the most reliability and the keywords climate change and crisis have the most prosperity. Also, the clustering of the researchers' intellectual developments from the analysis of the centrality index shows that they have gone through five intellectual stages. The general trend of researches on hazards and hazards management, topics related to climate changes and hazards caused by these changes, biological hazards caused by pathogenic agents, environment and environmental hazard, and finally, topics related to risk and natural disasters have been the most important steps.

Geologists on a global scale have called the fourth geological period the Quaternary period. The late Dr. Ahmad Motamed (1935-2016), a distinguished professor of Tehran University, is one of the scientists who have researched and studied the change of Quaternary processes in Iran. In many of his writings, coexistence with Quaternary has been recommended to his students and audiences. His scientific effort and theory can have a special aspect with elitist audiences and it is an extract of his known and intuitive knowledge. His death delayed the possibility of reaching the conclusion of his naturalistic thinking aligned with humanism and his virtuous thinking and social orientation. Criticism of thinking and ideas, epistemological criticism and practical criticism and the quality of the use of the natural environment by societies made them stronger in the Quaternary link with the policies and activities of politicians and civil engineers. Therefore, he tried to explain a theory based on a school, based on an ideal, based on a value and based on a science called "Quaternary". He saw the real needs of mankind and quaternary science as connected and related links. His systematic view is the beginning of scientific innovation in Iran's Quaternary knowledge. He tried to establish peaceful social relations of Quaternary.

Karstic water sources, in addition to their importance in providing water supplies, are highly vulnerable to contamination. Since the pollution in the karst water resources is transferred quickly and considering the tourism situation of this area, the physicochemical factors and the effect of the karst structure on the spread of pollution were investigated and an attempt was made to study the possibility of this area being karst and the factors of the spread of karst pollution. During the field visit, we investigated the type of formations, the structural features of the area, the extent of layering, the stratigraphic sequence at the location where the springs appear, as well as the geometrical and geological components that cause the structural obstacles. Samples from the springs were collected to study the hydrogeochemical characteristics.  AqQA and Phreeqc materials were used to examine the spring water results. We also utilized ArcGIS software and Excel to create the maps and carry out statistical analysis, respectively. The results show that except for S1, all springs have very hard water, indicating that calcium and magnesium are highly dissolved in the Mobarak limestone and Soltanieh dolomite formations. According to Piper's chart, all of the springs are in the classical bicarbonate range, indicating a carbonate source. Stiff diagrams also show that samples S3, S4, S6, and S7 are calcium bicarbonate, while samples S1, S2, S5, and S8 are magnesium bicarbonate. Except for the S6 spring, the region's springs have a low calcium to magnesium ratio, indicating that they are supplied by a dolomite karst aquifer. The Mann-Kendall and Tau-Kendall statistic values derived for most of the springs are negative, indicating a decreasing trend in spring water supply and rainfall in the region. Additional results include a high dissolution of calcium and magnesium in the aquifer's rock, a high relationship between underground water and formation. The region has dolomitic karst aquifers but lacks karst development and diffusion, as revealed by the water's prolonged residence time.  However, the interaction between karst and fractures indicates fractures and faults play an important role in groundwater flow. Water outflow through low-discharge fissures indicates the presence of diffusion flow, either turbulent or linear, in the studied area.

Dust storms are a severe form of air pollution that poses significant threats to the environment and human health. To deal with this phenomenon, it is crucial to comprehend the mechanisms accountable for dust generation. This can be achieved by utilizing machine learning in dust source susceptibility mapping. Although dust activities vary spatiotemporally due to the constantly changing atmosphere, few papers have addressed dust source susceptibility mapping considering Earth system frameworks such as wet and dry periods. Also, while optimizing hyperparameters is crucial for improving machine learning performance, many studies have neglected this aspect in this particular application. To address this research gap, the objective of this study was to create a framework for mapping the susceptibility of hazardous hotspot dust sources (HDS) during wet and dry periods (based on the changes in water bodies) using a fine-tuned random forest model with teaching learning-based optimization (TLBO) and student psychology based optimization (SPBO) optimizers. To achieve this, the study analyzed 10,392 identified HDS, along with various environmental influential factors between 2000 and 2020 in the transnational shared Tigris-Euphrates Basin, which is a significant source of dust in the Middle East and globally. The results showed that RF-TLBO performed slightly better than RF-SPBO, with an average mean absolute error (MAE) of 0.146, average root mean squared error (RMSE) of 0.194, and average Willmott Index (WI) of 0.761, compared to RF-SPBO's average MAE of 0.148, average RMSE of 0.195, and average WI of 0.757. The TLBO tuned RF with a lower number of trees and a lower maximum depth value, making it a simpler model. We utilized RF-TLBO and observed more areas that are more susceptible to hazardous dust sources during dry periods, confirming the meaningful relationship between wet and dry periods and hazardous dust susceptibility. Higher susceptibilities were found near water bodies and marshlands, indicating the significant impact of fluctuating water bodies on the generation of hazardous dust sources. The Gini index results also show that vegetation cover, elevation, wind speed, and soil texture have a high impact on land susceptibility to be a hazardous dust source.