Spatiotemporal variation of PM₂.₅ and its relationship with vegetation cover and meteorological factors during spring (2016-2022) in Riyadh, Saudi Arabia.

Fine particulate matter (PM₂.₅) is among the most critical environmental pollutants in Saudi Arabia, especially in the capital city of Riyadh, Saudi Arabia. This study investigates the seasonal and spatial variability of PM₂.₅ concentrations and evaluates the influence of key climatic parameters (wind speed, temperature, and relative humidity) during the spring season from 2016 to 2022. Data were collected from 16 monitoring stations and analyzed using descriptive statistics, correlation analysis, and GIS-based spatial distribution mapping. The assessment also considered the role of vegetation cover (Fractional Vegetation Cover - FVC) in mitigating air pollution across the city. The results showed clear variation in PM₂.₅ levels, with the highest seasonal average in 2018 (94.6 µg/m3) and the lowest in 2020 (55.0 µg/m3). Spatial patterns showed elevated concentrations mainly in southern and central Riyadh. PM₂.₅ concentrations showed a moderate positive association with temperature and weak negative associations with relative humidity and wind speed, although these meteorological relationships were not statistically significant. The relationship between FVC and PM₂.₅ varied among years; a statistically significant inverse correlation was observed only in 2016 (Spearman's ρ = - 0.539, p = 0.031, n = 16), whereas the correlations in the remaining years were weak and statistically non-significant. These findings indicate that vegetation may contribute locally to particle interception and deposition, but its influence on PM₂.₅ was not consistent throughout the study period. Overall, the results emphasize the combined influence of meteorological conditions, dust activity, and anthropogenic sources on air quality in Riyadh and support integrated monitoring and urban air-quality management.