Spatio-temporal analysis of PM_2.5 and its association with elevation by using remote sensing: the scenario of Quetta, Pakistan

Particulate matter (PM) includes the liquid or solid particles of various sizes that are suspended in the atmosphere, and are adversely affects air quality, ecosystems and human beings. This study involved the spatio-temporal analysis of PM_2.5 of the period from 2001 to 2021 in Quetta District. The specific objectives of this study were to analyze the concentration of PM_2.5 in Quetta District from 2001 to 2021, and to examine its association with elevation. The remotely sensed PM_2.5 data was retrieved from the satellite-derived global dataset (latest version V5.GL.03) having high resolution of 0.01◦×0.01◦. The assessments of dataset involve the integration of the retrievals of Aerosol Optical Depth (AOD)from various sources (including MISR, NASA MODIS and SeaWiFS) while the elevation data retrieved from DEM based on the Shuttle Radar Topography Mission (STRM-DEM) and ArcGIS 10.8 used for mapping. The results revealed that the highest midrange value (60.3 µg/m³) of PM_2.5 in 2003 and lowest midrange value (39.8 µg/m³) in 2006. Plus, the highest, lowest and midrange values of the concerned years were 57.1 µg/m³, 36.9 µg/m³ and 47 µg/m^3, respectively; which exceeded the permissible limits of WHO and Pakistan’s NEQS. Additionally, the highest elevation areas (2940–3300 m) contained low PM_2.5 concentration; and the areas of lowest elevation (1500 to 1860 m) had moderate to high PM_2.5 concentration. The elevation and PM_2.5 concentration showed strong correlation relation and risk for community. Consequently, by elaborating the phenomenon of the relation between the PM_2.5 concentration and elevation, this study can provide a baseline and can be potentially helpful for policymakers, planners and future researchers.