Background and Objective: Vegetation that is commonly used in urban design has a significant impact on air quality in the urban canyons. Thus, planners should be aware of vegetation impacts. In Isfahan metropolis, though vegetation covers a considerable portion of the city, the streets are encountered with pollution problems. In this study, distribution of pollution in urban canyons is evaluated using an optimal model for pollution reduction. Method: A three-dimensional modeling software called ENVI-met along with local and sub-climatic air quality model based on CFD-computational fluid dynamics-is used to study the influence of vegetation on pollution level in urban canyons. In this study, first a sample of real field and next a simpler version of the selected area are simulated. Findings: Different parameters such as height to width ratio in urban canyons, density of trees, location of trees in the streets and gaps between the trees are evaluated. Conclusion: The obtained results show that the increase of wind velocity in the shallow valleys is at the the lower level and the absence of natural obstacles such as trees reduces the level of pollution due to the high velocity of wind at this condition. When trees are located in the center of urban canyons, pollution and tree distances are inversely correlated and pollution level reduces by increasing the distance between the trees. In the other words, the pollution that is caught by the tree canopies decreases with the reduction in tree canopies.

The purpose of this study was to compare the physical and chemical characteristics of soils covered with vegetation and soils without vegetation in Dagh-e- Sorkh Ardestan area.To achieve the goal, first the vegetation was classified using physiognomic method, and for each vegetation type, the distinctive area was specified for soil and vegetation sampling. Vegetation sampling was done by stratified random sampling. Alongside pursuing the case, twenty two soil physical and chemical factors were investigated also for each growth type and area without vegetation. In the next step, to investigate the similarities and dissimilarities of the soils of desert areas by means of PC-ORD software, the cluster analysis was performe. After simplifying the one-way ANOVA, the most important soil factors which were effective in causing differences in the area’s soils were identified. Results show that the soils of area covered with vegetation differed much from the soils without vegetation physically in such a way that, the soil texture became heavier and gravel percentage became less in the areas without vegetation. Regarding the chemical characteristics, the frequencies of sodium, magnesium, calcium and chlorines and electrical conductivity were highly different. Because of topographic condition of land without vegetation, runoff is directed to this place and deposits salts there. Also, high groundwater level and capillary flowing salts are the important reasons for the salinity of this place. These are the limiting factors for the vegetation establishment in the desert areas of Ardestan.

Agricultural crops have damaged a lot due to the aftermath of late spring frost, and because low temperatures have damaging effects on agricultural production, it is essential to anticipate and prevent potential damages. Often, atmospheric temperature variations are very urgent due to the high temperature of the systems and the plants cannot adapt themselves with severe oscillations and, have been damaged. The aim of this study was to analyze the climate of the spring frost in Kermanshah, identifying the sea level equations and the late spring freezing frost of the period from 1990 to 2015. This survey has been done to determine the period of the freezing phenomenon, determine the minimum daily temperature of 7 stations placed in Kermanshah, Hamedan, and Ilam. After analyzing the data of spring frost freezing of Kermanshah province using the main component analysis technique and hierarchical clustering method, the most common 10 patterns of late spring coldness of the area were studied and determined. In 10 resulting cluster, 8 clusters were related to the high-pressure pattern of Siberia. From the total 91 days of spring frost freezing in Kermanshah province (79% (72 days)) is due to the high rainfall of Siberia, 12% (11 days) is due to the Mediterranean climate and 9% (8 days) is due to the Van lake climate. These pressure patterns were named according to the location of their deposition, which caused the loss of the environment and the freezing frost of the spring.

Examining housing quality issues, among other things, is one of the key issues in housing planning. Housing is a physical place that is considered as a shelter and basic need of the family. The quantity and quality of housing reflects the socio-economic status of the city and many realities of society. Housing is an integrated part of the development of the national economy. Addressing housing indicators as the main planning tool can be considered as one of the most sensitive stages of planning. In order to ensure social growth, the housing sector, in addition to the housing unit itself, also includes the environment around it. Certainly, identifying housing quality levels in different urban areas is an effective step in explaining the quality of life and the sense of satisfaction of city dwellers. The indicators examined in the present study include indicators related to safe housing with sustainability and structural durability and a suitable living space. In the present article, an attempt is made to evaluate the quality of housing in Urmia metropolis based on available statistics. For this purpose, descriptive and analytical methods have been used based on the data available in the Statistics Center of Iran. The raw data in the Excel spreadsheet was converted to 35 indicators and entered into the SPSS software to perform factor analysis on them. To perform factor analysis, eight factors were identified, four of which were primary and the other secondary. The factors were then entered into the GIS environment and analyzed. The results indicate an unequal and inappropriate distribution of quality housing indicators in the city of Urmia. The results showed that 18. 21% of the statistical areas are among the most deprived areas, 18. 18% are deprived, 53. 53% are average, 18. 13% and 57. 9% are completely deprived. It seems that more attention should be paid to areas 1, 2 and 3 to reduce inequalities to some extent. The results of this study showed that deprived clusters are appeared in regions 3 and 2, and delighted clusters in regions 1 and 4. This situation indicates the existence of class distance and dichotomy in urban space and the difference in having the studied indicators in 2011.