Spatial and Temporal Analysis of Methane Pollutant Distribution in Metropolitan Areas Using Remote Sensing and Geographic Information Systems (Case Study: Isfahan Metropolis)

Background and Objectives: Air pollution is one of the major environmental and health challenges that has been exacerbated by industrial growth and increased human activity, particularly in large and industrial cities. Methane gas, as one of the most potent greenhouse gases, plays a significant role in global warming, climate change, and the deterioration of air quality. The sources of methane emissions include wetlands, livestock farming, agriculture, and landfill sites, with human activities contributing significantly to its increase. Measuring and monitoring air pollution often faces spatial and temporal limitations due to ground-based monitoring stations. In this context, satellite data, due to its wide coverage, cost-effectiveness, and ability to provide high spatial and temporal resolution data, is used as one of the most important sources of information for studying air pollution. This research utilizes data from the TROPOMI sensor on the Sentinel-5P satellite, which enables the measurement of methane concentrations in the atmosphere, as the primary data source. These data serve as the basis for spatial and temporal analysis of methane distribution in the Isfahan metropolitan area, providing an opportunity to closely examine the spatial and temporal patterns of this pollutant on a large scale. Despite the high importance of methane pollution, no comprehensive study has been conducted regarding the spatial and temporal distribution of this pollutant in Isfahan. The aim of this research is to conduct a comprehensive and systematic analysis of methane distribution in the city of Isfahan using satellite data and identify the relationship between atmospheric changes and methane variations to offer effective solutions for air pollution management and environmental quality improvement.

Materials and Methods: This study aims to analyze the spatial and temporal distribution of methane concentration in the Isfahan metropolitan area using TROPOMI sensor data from the Sentinel-5P satellite over the period from 2019 to 2023. Satellite data were retrieved, processed, and analyzed using the Google Earth Engine platform. To examine the spatial distribution pattern of methane concentration, the Global Moran’s I index and G-statistic were applied to analyze clusters and determine the data dispersion. Additionally, the Gi-statistic was used to identify areas with the highest (hot spots) and lowest (cold spots) methane concentrations. Furthermore, the relationship between methane concentration and climatic factors such as temperature, air pressure, precipitation, and wind speed was evaluated through the calculation of Pearson’s correlation coefficient. Finally, the temporal trends of methane concentration were analyzed on a monthly, seasonal, and annual scale.

Results and Discussion: The results from the analyses indicate an increasing trend in methane concentration in the Isfahan metropolitan area during the study period. This gas experienced the highest concentrations in the colder seasons, especially in industrial and agricultural areas. Spatial analyses revealed significant clusters of high concentrations in the northern regions, particularly in areas 4 and 7, as well as in the eastern areas, particularly in areas 12 and 15. These high methane concentrations were linked to activities such as livestock farming, agriculture, and landfill operations. In contrast, the southern regions, particularly areas 2 and 6, as well as some parts of the western areas, were identified as cold spots with lower concentrations. Furthermore, the assessment of the relationship between climatic parameters showed an inverse correlation between temperature and wind speed with methane concentration changes, while air pressure exhibited a positive and significant relationship with the gas concentration changes.

Conclusion: The results of this study, based on high-precision satellite data analysis and advanced spatial measurement techniques, provide valuable information for air pollution management and urban planning. Accordingly, it is recommended that methane emission monitoring and control be prioritized during the colder seasons, with a focus on the identified hot spots. In this regard, optimizing industrial processes, efficiently managing waste in the eastern parts of Isfahan, and controlling methane emissions from northern livestock farms using modern technologies, including bioremediation methods, can play an effective role in reducing this pollutant. Additionally, the use of remote sensing data and advanced predictive models for continuous methane concentration monitoring and targeted pollution control strategies is recommended as an effective approach.