Investigating the Relationship between Urbanization and Air Pollution Using Google Earth Engine Platform: A Case Study of Istanbul
Duygu Yasan, Uğur Acar, Osman Salih YılmazRapid population growth, industrialization, urbanization, loss of green areas, increased vehicle traffic, and heightened fossil fuel consumption in megacities like Istanbul have led to various impacts. These effects contribute to an increase in air pollution within urban areas. Rapid urbanization and heightened air pollution in megacities can lead to serious environmental, economic, and health problems. Therefore, understanding this relationship and identify its impacts is crucial. This study aims to examine the relationship between urbanization and air pollution in Istanbul. For this purpose, land cover maps covering Istanbul province were produced using Landsat-5 (TM), Landsat-8 (OLI), and Sentinel-2 (MSI) images from the years 1996 to 2021, at three-year intervals, on the Google Earth Engine platform. Land cover for classification purposes was divided into five different classes: forest, water surface, urban area, bare land, and classified using a random forest machine learning algorithm. To examine the impact of urban area growth on air pollution, the second step of the study involved analyzing the column number density values of SO₂, NO₂, CO, and O₃ gases from Sentinel-5P (TROPOMI) data for the years 2019, 2020, and 2021. The averages of the data from 39 air pollution monitoring stations across Istanbul were also examined. According to this classification, the urban area expanded from 491 km2 in 1996 to 1222 km2 by 2021. Considering the total surface area of Istanbul province, the proportion of urban area increased from 9% in 1996 to 23% by 2021. The TROPOMI values were calculated as follows: the average column number density values for SO2, NO2, CO, and O3 were 0.0003538 mol/m², 0.0339514 mol/m², 0.0000984 mol/m², and 0.1453515 mol/m², respectively. Similarly, the gas concentrations of SO2, NO2, CO, and O3 measured from the ground stations were calculated as 6.603 µ/m3 , 786,815 µ/m3 , 43.763 µ/m3 and 45.773 µ/m3 , respectively. Correlations between urbanization and TROPOMI values revealed a positive correlation of 0.39, 0.02, and 0.80 for SO2, NO2, and CO gases, while a negative correlation of 0.25 was found for O3 gas. The study also examined correlations between TROPOMI and ground station measurements, resulting in positive correlations of 0.55, 0.66, and 0.16 for SO2, NO2, and CO gases, respectively, while a negative correlation of 0.05 was found for O3 gas. Based on these findings, among the air pollutants studied both through TROPOMI and ground station data, the highest correlation was observed for CO gas. These results provide an important source of information for understanding the environmental impacts of the urbanization process in megacities and for developing strategies to reduce air pollution. They also demonstrate that methods such as remote sensing and atmospheric data analysis are effective tools for understanding and solving environmental problems.
