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Volume 1, Issue 1 (4-2014)
Nowadays air pollution in large cities such as Tehran have dramatic effects on public health, hence study of the way air pollutions varies with meteorological parameters appears to be important. One important aspect of sustainability of large cities such as Tehran, is controlling the emissions of pollutants as the meteorological (climatic) conditions are becoming more acute in terms of air pollution and temperature rise. In this paper some recent records of near surface meteorological parameters as well as some pollutants records are examine to observe how they change daily, monthly and annually and how they are correlated. Considering the variations of winds and temperature (extracted from a 2D sonic anemometer at 10 m at the Institute of Geophysics, Tehran University in the northern part of central Tehran, with one minute intervals) and hurly data of CO and PM10 concentrations for the same station for 2007, their relations were investigated. Also using upper air meteorological data (at 00.00 and 12.00 UTC) from Mehrabad Airport station, the stability of the atmosphere during this period was analysed. Here the buoyancy frequencies that are measure of stability of air column were calculated. For averaging of winds two methods based on the real wind vectors and wind unit vectors were used. By correlations between the pollutants concentrations and meteorological parameters, their relationships were considered. Based on the probability distributions of winds for 2007, it was found that most of the time wind speeds were in the range of 0.5 and 2 m/s. Hence most of the time due to this weak wind there was a condition of air pollution accumulations over the city and only local winds could move the polluted air over the area. Annual cycle of variations of mean surface winds had small amplitude that appears to be due to high mountain ranges that surround the city from north and east. The annual cycle of CO variations showed a peak in autumn and winter while PM10 amounts showed a trough in winter and spring. The higher values of CO in winter seems to be due to the surface temperature inversions and improper burnings of the fuel of vehicles as well as the domestic heating systems. This was indicated in the correlations between temperature and CO concentration. In annual cycle the correlation between CO and PM10 concentrations was about 0.4 which increased to 0.7 for spring time. This may indicate that in this season the sources of these two are similar and one of them may be used to estimate the others is the sources are not changed. There are two maxima in the daily variations of CO which coincides with minima of wind in morning and evening transition times. In this study it was found that due to calm meteorological conditions (often od local origin, called mountain breezes) over the city air pollution problem is a serious problem requiring more emission control. Also trend factors as the pollutant sources (traffic) and the depth of the atmospheric surface layer are important. It is particularly noticeable that during the midday as the depth of the mixed layer increases, the air pollution concentration is reduced substantially. At night surface drainage flow from north of the city and surface radiation cooling creates near surface inversions that can limit mixing and ventilation of the polluted air from the area leading to higher values of gaseous pollutant over the city. Also lager stability in the air over the city at higher levels in autumn and winter is due to subsidence inversions as a result of the prevailing meteorological conditions of high pressure systems over this area in these months. Such conditions seem to have increased the creation of more acute conditions for air pollution over the city. For a more resilient city in terms of air pollution, some mitigation need to be undertaken in the face of climate change effects that are deteriorating the atmosphere of the city.
Volume 10, Issue 2 (9-2023)
Today, in addition to exploiting environmental resources, humans must be able to recognize environmental hazards and try to reduce their damages. The location of Iran in the Alpine-Himalaya mountain belt has made Iran one of the high-risk seismic areas, and the east of Iran is no exception to this rule. The fault activities of eastern Iran, especially east and west of Lut, are a serious threat to the residents of eastern Iran. The activity of old and young faults and the emergence of new faults have provided the basis for the occurrence of destructive earthquakes in these areas. And it still continues and has been able to provide problems for the population living in the east of Iran.
The purpose of this research is to investigate the role of the Giv fault system in the occurrence of morphotectonic evidence and active tectonic analysis in the studied area, which has achieved favorable results according to the model used and the studied sources. The model used in this research, which is derived from similar examples in foreign sources, mostly deals with the destructive aspect of tectonics and has achieved the desired goals. Based on this, it should be seen if the morphotectonic evidence of the Giv fault system can be a sign of more activity and more threat in this part of the range (southern domain of Baghran mountains) or not? After studying various sources, the sources that answer the research questions were selected and further analyzed, and the conceptual model derived from these sources, which has a qualitative-analytical aspect, was used. Therefore, according to the main objectives of this research, which follows the destructive and instantaneous tectonic aspect, sources were selected that provided the most information to answer the research question, the sum of the information expressing the active tectonics in the studied area.
Research Methodology
The Giv fault system is a part of the Nehbandan-Kash fault in the east of the Lut block, and in the Giv plain, north-east of the Lut, with an almost west-east direction, it passes through the south of the Giv village and continues to Deh Mir and Karijgan in the west of the Giv plain. Giv village is located in Khosf County in South Khorasan province and in the center of Giv plain, south of Baghran Birjand Mountains and north of Shah Mountain.
The current research is of applied and developmental research type, and according to the history of seismicity of the region and historical data, it can be a step in the direction of knowing the seismic risk areas and also reminds the local residents to be more prepared. The conceptual model used in this research, which is derived from similar foreign examples, examines mostly the destructive aspect of tectonics.
In this research, the library work started by collecting and receiving a series of domestic and foreign sources, followed by the translation of foreign sources over a long period of time. Also, statistics and information were received from Geological Organization and Geophysics Institute, Birjand University, Birjand Seismological Center. Field studies, interviews, surveys and field measurements, using geological and topographic maps and satellite images, and using Google Earth and Arc GIS software, analysis and synthesis of information were carried out. Most of the data were used as qualitative data and to some extent quantitative data in the analysis.
Result and Discuction
The morphotectonic evidence in the studied area indicates a high risk of seismicity in the Giv fault pack, which is more dangerous than other parts of the Giv fault system.All the evidences such as uplift and cliffs in the south of Giv, significant change of the bridge river near the mouth and bed digging in this section show the uplift and activity of the South Giv fault and the travertine formation associated with the earthquake in the south of Giv, as well as the evidence of the growth of the Young Giv fold in 5 km. North of Giv village, such as the deviation of Pol and Minakhan rivers and excavation of the Minakhan river bed (Antecedence phenomenon), the presence of three generations of alluvial fans in the vicinity of the Young Giv fold, all indicate active tectonics and the rise of the Giv fold and the occurrence of destructive earthquakes. All the above-mentioned evidences are a serious alarm for the residents of Giv fault, especially Giv village, and require more study work, strengthening of villages, and proper planning for construction works so that the past tragic events of Giv village do not repeat in the future and this issue is taken into consideration in the discussion of land development.
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