مجله مخاطرات محیط طبیعی
پیاپی 32 (تابستان 1401)

In this study, the trend of tropopause changes in the Iranian atmosphere in the spring and autumn months was analyzed using ECMWF database data from 1979 to 2018. The results of studying the trend of tropopause changes in spring and autumn showed that in large parts of the country the observed trend was without statistical significance and only in March in parts of the west and northwest of the country and in September in the Zagros Mountains was positive and statistically significant. The results of studying the temperature trend of two levels around the tropopause also showed that in all months of spring and the first two months of autumn, except for very limited areas of the country, the observed trend is without statistical significance. The two-level temperature trend around the tropopause in November was significantly different from other months under the study; this month, large parts of the country were statistically significant in the two levels around the tropopause. Examination of the temperature difference trend of the two levels around the tropopause also showed that in areas with a significant trend, the trend of the difference between the two levels of high and low tropopause was negative. Analysis of Variance, Skewness and Kurtosis Tropopause trends also showed that in the three months of spring in most areas the observed trend is not statistically significant, but in autumn (especially September) in some parts of the country, the observed trend is significant. According to the results, it can be said that during the last forty years, the effect of climate change on the tropopause layer on the Iranian atmosphere in spring and autumn has been very small and changes in spring have been much more limited than in autumn.

One of the critical factors dust sources by less consideration is the role of geology and geomorphology as a source of dust emission. Geological units are one of the factors involved in the release of dust particles and the production of sediment.  Lithological components with high sensitivity to alteration, weathering, and erosion, play an influential role in the emission and distribution of dust particles. Based on research, Sarakhs County is one of the critical corridors of wind erosion and dust storms in Iran that is affected by 120-days’ winds of Sistan The sensitivity of the geological units to wind and water erosion in this area categories from medium to very high. To identify the chemical elements of the geological units and their roles in dust emission, soil samples were collected from the surface, and sub-surface layers of the geological units and airborne dust were also collected from the atmosphere. Samples were analyzed by induction spectroscopy to determine their chemical elements. To identify the origin of dust and its relationship with geological units and also their classification, factor and cluster analysis was performed. The results of factoring and clustering analysis showed the Sarakhs region with chemical elements sodium, zinc, lanthanum, arsenic, niobium, cadmium, nickel, lead, zinc, lithium, strontium, sulfur, sodium is in factor one with an evaporative and chemical origin, and with elements of aluminum e, iron, cobalt, thorium, manganese, boron, and titanium is in factor two with a detrital and terrestrial origin. Also, the chemical elements of dust in rural areas of Bazangan, Shorlugh, Baghbghoo, Padeh, and Baghak are in the same group with the geological units of Abe-Daraz, Chehel-e-Kaman, Quaternary deposits, bitter water, and Khangiran and have a common origin. The chemical elements barium, arsenic, sulfur, thorium, nickel, lithium were introduced based on enrichment factors with human origin (chemical-evaporative).

One of the affective dimensions in measuring the level of urban resilience against urban floods is the physical-infrastructural dimension which through it the state of society can be assessed in terms of physical and geographical characteristics affecting the occurrence of floods. Irregular and uncoordinated development of Chamestan urban area due to human activities for the development of the city has directly changed many areas of the city in a very short time, as a result of which, risks such as floods are created. This study aims to analyze the relationships between factors affecting the physical infrastructure resilience of Chamestan city against urban floods. Indices of physical-infrastructural resilience according to the study area, including access, construction, and distance from the natural hazardous environment, were examined in the form of 12 sub-indicators. After standardizing the sub-indices with fuzzy membership functions, to overlap them and prepare the three mentioned indices, the process of hierarchical analysis and expert opinions were used. Access to health centers (0.374) is the most important sub-indicator of access, building quality (0.647) is the most effective variable of structure and building index, and distance from the river (0.643) is the most important sub-indicator of distance from the dangerous natural environment. According to the final zoning map of physical-infrastructural resilience, most of the area of Chamestan city, central and northern parts of the city, is located at the level of physical-infrastructural resilient or relatively resilient against floods. The northern part of the city, which is the main core of Chamestan, is in the categories of non-resilience and low physical- infrastructure resilience.

Geomorphological forms each at different stages of the process of environmental change and evolution, stable conditions and instabilities under the influence of external and internal processes. One of these forms is igneous masses, which take on a distinct shape and change due to tectonic movements and fault movements. This change can be shown using geomorphological evidence and indicators. The igneous massif is located beyond the Sanandaj-Sirjan metamorphic belt in the western part of Qom province. By examining different patterns such as drainage pattern, color tone, slope, circular rings and geomorphological indices, mass growth was revealed in this area. The pattern index completely indicates the instability of this mass. Most of the surfaces of the alley mass slopes are composed of triangular shapes, the formation of which is the result of the performance of active internal processes against external processes. The color tone of this cone is light and indicates that it is active. The circular rings of the mass indicate the expansion of the eastern slopes. The slope of this mass between 5-10.5 which is justified by tectonic action and all the alluvial fans of the surface morphology is in the form of ducts and small ridges And 2 cases of erosion were observed in the southeastern part of the intrusive mass, which is advancing towards the top of the alluvial fan. Captivity and diversion of waterways in the region is another piece of evidence that is influenced by active tectonics. Due to the instability of the slopes and alluvial fans, no human activity (except in special cases) has been formed in the area. In general, the indicators and evidence of instability and active tectonic movements in different parts of the intrusive rock of diorite and the lack of news of the day. Due to the active tectonics and instability of this environment is fully approved.

Urban environmental pollution by heavy metals causes undesirable changes in the physical, chemical, and biological properties of life's main sources including water, air, and soil. This study has been carried out to map the spatial distribution concentration of heavy metals copper, zinc, lead, and cadmium and to evaluate the ecological and environmental hazards of these pollutants, by pollution indices mCd, Igeo, RI, and Cf indices in Zahedan city. In this research, 90 samples of deposited dust were collected by using a systematic random sampling method, and the concentrations of these metals were measured. To the model of the spatial distribution of heavy metals, the kriging method was used in Arc GIS. The results of heavy metals concentration measurements showed that the highest mean concentration was obtained for Pb 270.51 (mg. kg-1) and the lowest mean concentration was obtained for Cd 20.74 (mg. kg-1). Also, average concentrations of lead and cadmium were higher than the standard level in the soil. Also, the results of the Pearson correlation coefficient showed that there is a significant correlation between zinc and cadmium. Based on the results of the contamination factor and the potential environmental risk index, the copper and zinc showed low pollution range, lead high pollution range, and cadmium very high pollution range. Geoaccumulation index showed moderate pollution class for cadmium and high pollution class for copper, lead, and zinc. According to the spatial distribution maps, the highest concentrations of metals were observed in the city center and main roads which showed the role of human activities in the distribution of these elements.

Today, about 60% of the world's energy resources are oil and gas. Due to the different methods of transporting crude oil and its products, the largest share of the transfer of these resources is through the transmission pipeline lines. The present study aims to model the GIS model of fire-based urban gas distribution networks and the seismic effects of Tabriz in intensifying fire. For this purpose, multi-criteria decision-making methods (MCDA) with geographic information systems (GIS) were used. Also, to determine the importance of the relationship between criteria and sub-criteria and their relative importance coefficient, the FANP model was used. And 20 sub-criteria were studied to study the vulnerability to gas network fires. To determine the effect of seismicity of Tabriz city on fire in urban gas distribution networks, the seismic hazard zoning map of Tabriz city was compared with the output map of the present study and it was determined that the most vulnerability in both seismic hazard map and fire zoning map The gas network is in the northern and northwestern part of the area, which is a worn and marginal part of the city. Residential use with 70.63 hectares with the most damage from the fire of urban gas distribution networks due to earthquake intensification is in the first place. Considering the high risk of fire in urban gas networks, in the region, especially the worn-out and marginal structures, it is necessary to organize these structures and carry out protective operations of gas transmission lines in the mentioned issues. Also, according to the results of the research, the complexity and length of gas transmission lines in the suburban fabric of the city are high, so it is recommended to use polyethylene pipes in these areas, which have a high resistance to steel pipes.

Nowadays, the air of most of Iran cities especially high population metropolises hasn’t an optimal quality. This adverse quality is due to various pollutant resources such as automobiles, industries, heating devices, construction, and commercial activities during recent decades and there are more concerns about it. Therefore, monitoring air pollutants and studying their seasonal and spatial variations are specifically important. The present study aimed to evaluate air quality and seasonal and spatial variations of particulate matter (PM2.5 and PM10) in Tehran city. In this research, the AQI index has been used to determine the air quality of Tehran and to introduce the responsible pollutant. To investigate the variations of particulate matter (PM10 and PM2.5) in seasonal and spatial scales, the data of air pollution monitoring stations (18 stations) of Air Quality Control Company used during 2018 and 2019. Data were analyzed using Excel and SPSS software and results of statistical analysis of pollutants distribution in Temporal – spatial scales are provided and they are drawn using Arc GIS software and analytical function of inverse Distance Weighting interpolation (IDW) as maps, tables, and graphs. Based on the results, favorable and unfavorable air quality were respectively observed in 83.8 and 16.2% of days in 2018, as well as 76.4 and 23.6% of days in 2019, which can be related to the changes in rainfall rate and wind speed in the years. The maximum seasonal concentration of particulate matter (PM10 and PM2.5) relates to summer and winter respectively and the minimum seasonal concentration of both pollutants relates to spring. Results of inverse Distance Weighting interpolation (IDW) also showed that the west, south, central regions of Tehran got involved with particulate matter more than other regions.

Due to the earthquake damage caused by the earthquake, one of the most important issues which is considered by the authorities after the earthquake is the water supply of citizens of a city. Unfortunately, in many cities of Iran, the management of the crisis, especially concerning drinking water, is not noticed in the aftermath of the various events that the metropolitan is considering. due to the great importance of this issue, in this study, suitable spaces to locate water emergency reservoirs in shiraz, based on criteria urban public open spaces (park and green space, open space Stadium, city Squares), Population density (near Population block whit high Population density), roads network (access to roads high way, main road, minor road), high-risk centers against Earthquake (wearing texture areas in the slopes areas Close to the fault, Historical points of the earthquake) Based on the hierarchical analysis Process (AHP) and decision support system, GIS, (using of transformation functions of a polygon to point, vector to raster, Euclidean distance, reclassify and the functions of a scalar subset to be evaluated. The results of this study suggest the locations with the scores of 7,8,9, that located mainly in destroyed texture areas, regions with high population density and urban main roads of Shiraz as the alternatives for locating of the city's emergency water Resviors.

Precipitation is the most important climatic characteristics of any region. This climatic characteristic is one of the most fluctuating climatic variables that seriously affects the water resources the region. This issue is  important in Iran, where the average rainfall is over 250 mm. The purpose this study is to analyze and explain the heavy rainfall  Karkheh and Dez using statistical methods. For this purpose, precipitation data from 14 synoptic stations and rain gauges period 60 years (1959-2019) were used. In order to achieve the objectives  the research using the probabilistic distribution function the final limit  type 1 Gumble, the heavy rain threshold each station was determined. Then to identify the uniform and non- uniform discharges in the time series maximum daily precipitation and total annual precipitation the ITA method and Man – Kendall non-parametric test were used. The results were obtained from heavy rainfall thresholds, The average rainfall of more than 40/7 mm in Karkheh and the average rainfall  more than 47 mm in Daz  are considered as heavy rainfall. The average rainfall in Karkheh is 118 days and the dose  is 81 days. The flood threshold of Karkheh  is less than Dez catchment. Therefore Karkheh rains occur more suddenly and irregularly while Dez  have more normal time series. As a result Karkheh is more vulnerable to floods than Dez in terms increased heavy rainfall. The results of using Man – Kendal and ITA test showed that Man – Kendal test can only detect uniform trends in time series as the advantage ITA method is that in addition to uniform trends. It is able to detect hidden trends and internal in identify time series. For example, although man – Kendal test did not show a specific trend for maximum rainfall at Khorramabad station, The ITA test detected hidden and non-unform trends for this station.

The occurrence of catastrophic floods in March-April 2019 in Lorestan province was a clear example of heavy rains that caused very heavy damage to agricultural, urban, transportation and communications infrastructure.  The purpose of this study is to investigate the March-April 2019 rainfall in the Droud-Borujerd catchment area in terms of statistical, synoptic and dynamic characteristics. In this regard, from the data related to the daily station rainfall in March-April 2019 of Boroujerd and Dorod synoptic stations, NOAA climate Synoptic factor data for the 25th March and 2th April 2019 and upper atmospheric data from the University of Wyoming database for the mentioned days of April 2019. The results of statistical analysis showed that the occurrence of rainfall in April 2019 was one of the heavy rains that in the first wave (25th March) 2019 was 15% of the total annual rainfall and in the second wave (2th April 2019) 20% of the total annual rainfall was recorded. Analysis of synoptic patterns of these heavy rainfall events showed that a similar synoptic pattern produced these two waves of heavy rainfall in the region. On both days, the presence of a strong trough a height of 5500 and 5550 geopotential meters, on the east of the Mediterranean Sea that the western region of Iran located in the front of this trough, lead to heavy rainfall. In these two days, the omega index had reached a significant critical value (-0.2). Moisture injection in the study area was done by the interaction of two cyclonic systems (east of the Mediterranean Sea) and anti-cyclone (on the Gulf of Aden) and the source of moisture supply was the Mediterranean Sea, the Red Sea and the Persian Gulf, respectively. High atmospheric instability indices did not confirm the existence of very severe instability in the region. Moderate instability in the lower levels of the atmosphere, which could not be extended to the upper level (Skew-T diagram), indicated that a global synoptic system was involved in the whole region and no local convection factor played a role.