Journal of Spatial Analysis

Air pollution has become one of the main problems of cities. Among the sources of air pollution, vehicular traffic plays an important role. Planning for efficient management and control of the air pollution caused by vehicular traffic requires accurate information on spatio-temporal dispersion of the pollutions. This research studies 3D spatio-temporal dispersion of NOx pollution caused by vehicular traffic at Valieasr-Fatemi intersection resides in Tehran, Iran. It is selected for being crowded and having the required meteorological and pollution data sensed by the Air Quality Control Corp. of Tehran Municipality.

This study uses GRAL that is a local micro-scale air dispersion model defined based on Euleran-Lagrangian dispersion models. It investigates the level of spatio-temporal autocorrelation generated by GRAL simulations at both 2D and 3D modes and discusses how it adapts with the reality.

Adopting the GRAL air pollution dispersion model, streets are defined as the linear source of pollution of NOx caused by vehicular traffic. The traffic rate is estimated based on street areas and directions, the designed average traffic velocity, traffic volume and car passage counting at the intersection. The 3D geometry of the buildings is also added to the model. All the required data that were available for winter of 2007 are gathered and introduced into the model.

The model is executed at 9 heights vary from 1.7 m to 52.5 m. These heights are defined covering a range from an average human level height to average building height and above. These levels are considered both separately in 2D mode and integrated into a 3D mode. The formation of NOx clusters is investigated analyzing their autocorrelation using Moran Index at global and local scale.

The calculated Moran-I at global scale at each 9 levels of heights, varies from 0.7 to 0.9 that depicts the validity of the GRAL model adopted to simulate the expected autocorrelation of pollution density affected by spatial issues. The Moran-I increases at higher levels as less air turbulence happens. However the result show that the turbulence increases temporarily at about 10m to 15m which are the average building heights. At local scale, the Moran-I/Anselin shows that HH clusters dominate at lower levels, around streets central areas that are farther from the buildings, and around the intersections. At higher levels, esp. higher than buildings average height, the LL clusters dominate. However the HH clusters formed around intersections, while are shrank, are still visible at high levels. The turbulence caused by building fronts and their down wash effect is also shown in the result as no definite cluster is formed near the buildings front and back.

The autocorrelation analysis is also carried for an integrated 3D model consists of all the 9 levels of heights. Considering the weight matrix for a 20m 2D neighborhood and 1m/s dispersion of the pollution vertically, the global calculated Moran-I equals 0.229 which shows existence of a spatio-temporal autocorrelation of the results generated by GRAL. At local scale the results show that the HH clusters have higher temporal dispersion rate than LL clusters.

The City-region of Tehran is encountered with various environmental problems, including traffic, air pollution, lack of drinking water and green space, physical texture conflict, flood and earthquake. Capital accumulation has considerable role in shaping spaces which can create and intensify environmental disaster in special socio-economic situation. The second cycle is the conversion of capital to fixed and long-term assets with the aim of further benefits, which in fact produces two types of artificially environment during this process namely the built environment for production, and the built environment for consumption.

The third cycle is aiming to connect science to production and increase production capacity by investment in science and technology. When production of surplus value reduced in the first cycle, surplus value of second cycle increases through speculation and real estate transaction (real estate capital). Therefore, the owners of the lands and buildings are encouraged in production, trade and supply of these type assets.

In the courtiers that are legally and administratively encounter with tax receipt problems,  urban lands ownership is deposited to market system without any control, hosing transaction continues without any limitation, situation is moving forward to personal vested interests, asset value rises rather than production value, the price of land and construction increase severely. In the above mentioned condition, beneficiaries attempt convert the natural resources including park, mountain, river privacy and road privacy to marketable commodity and legally or quasi legally seize them. Therefore, unreasonable construction and population density increases and city-region will encounter with environmental disasters.  

The main objective of this research is to understand the underlying factors of capital accumulation through construction and its impacts on createion and intensification of environmental disasters in the Tehran city-region.

  Five different regions of Tehran were selected for data collection. "Q-methodology" was used for gathering and analyzing data. The society of communication or people whom the study sought to identify their mentality towards the research topic, were 25 experts selected through purposive sampling. To set the concourse of communication, a combination of primary (experts commented in an interview) and secondary (sources of credit) sources have been used and   34 statements have been developed. After sorting the data for analysis, SPSS software data matrix is ​​formed. Factor analysis, as main method of analyzing Q data matrix has been used based on Q logical methodology.

The results of Q analysis depicted four viewpoints with variance of 95.911 percent on the underlying cause of capital accumulation through construction and its contribution on increasing risk of natural hazards in Tehran city-region.

The first viewpoint has devoted 52.800 percent of total variances and can be titled as" Function of real estate transaction and Non-productive economic domination".

The second viewpoint which has received 18.914 percent of total variances is accordance with "commodification of land and housing". The third viewpoint is" management and monitoring of the city-region space" with 15.163 percent of total variances.  The fourth viewpoints under the title of" monitoring and control of natural resources" has assigned 9.034 percent of total variances.

As result of these processes, land and housing business have weakened society's productive capacity by extensive land use change in the urban peripheral area's due to its huge and quick profit. The above process accompany with selling excess density policy created a powerful political and economic stratum which harmed city sustainable development. The mountainous area of north, north east and west of Tehran, have annexed to metropolis as a result of above mentioned regulation and  may gardens have converted to construction by different gropes and institutions.

Q method analysis depicted that the Tehran City-Region has converted from use value to exchange value. It means that values of the city including work, security, education, leisure and welfare have been lost in favor of exchange value. In other words, the city has been converted to a commodity for exchange and selling in pursuit of profit, rising cost of urban land, building and housing. Consequently, the city-region construction site is extended to the river beds, steep slops and surrounding natural environment. This in turn is leading to rapid land use change and violation of environmental and spatial rules and regulations and intensification of environmental hazards.

Today, air strike on installations and urban areas, is normal. As such, vulnerability assessment cities and provide the right solution for harm reduction is essential. The purpose of this investigation was to identify factors causing damage in the district of twenty in Tehran. The research method is descriptive-analytic and Data collection is library and field. Data analysis is based on using Ahp and GIS. Results show, In the district twenty , There are three zones vulnerable. Including, The old Central, The high-density Dolatabad and sizdah aban neighborhood. These zones are 34 percent of the land. The reason of it is Poor physical structure. Statistical Society is Twenty district in Tehran. Sample size is 384 people of residents of the district. Because, in this area there are strategic factors, is An important part of the tehran city. in the end, are provided The right solution of Reducing vulnerability.