A Novel Viewpoint to the Green City Concept Based on Vegetation Area Changes and Contributions to Healthy Days: A Case Study of Mashhad, Iran

Abstract One of the significant challenges in urbanization is the air pollution. This highlights the need of the green city concept with reconsideration of houses, factories and traffics in a green viewpoint. The literature review confirms that this reconsideration for green space, has a positive effect on the air quality of large cities and to remove the air pollution. The purpose of this study is to evaluate the annual vegetation changes in the green space of Mashhad, Iran as a very populated city in the middle east to study the air pollution. To investigate the relationship between the air pollution and vegetation, the Landsat 8 satellite images for summers of 2013-2019 were used to extract changes in vegetation by calculating the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and the Optimized Soil Adjusted Vegetation Index (OSAVI). The main contribution in comparison with the relevant studies is to study the relationship between clean, healthy and unhealthy days with the green space area for the first time in Mashhad, Iran. The results show that the implementation of green city concept in Mashhad, Iran has been increased by 64%, 81% and 53% by NDVI, EVI and OSAVI, respectively during the study period. The vegetation area of this city is positively correlated to clean and healthy days and has a negative correlation to unhealthy days, in which the greatest values for NDVI, EVI and OSAVI are 0.33, 0.52 and -0.53, respectively.