Long-term perspectives on land-use changes and air pollution policies in Iran: A comparative analysis of regional and global patterns in atmospheric PM.

Fine particulate matter (PM) pollution is a major environmental challenge across the Middle East, including Iran. However, a substantial lack of knowledge exists regarding the linkage between aerosol trends, specific compounds, and their interrelation with emissions, mitigation strategies, and land changes. This research comprehensively evaluates the spatiotemporal trends of PM and its main precursors (SO and BC) concentrations in relation to LULC (Land-Use and Land-Cover) changes and mitigation policies in Iran during 1980-2023. Surface PM concentrations were estimated using five monthly MERRA-2 simulation datasets, including sea salt, dust, BC, OC, and SO. The Evaluation of MERRA-2 PM against ground-based measurements confirmed that the MERRA-2 reanalysis data is ideal for monitoring PM patterns in Iran. Our trend analysis showed that dust dominates high PM concentrations in southwestern and southeastern Iran during summer, while anthropogenic aerosols (SO and BC) are the most significant contributors to PM in urban areas like Tehran in winter. Overall, a significant rise in aerosol occurred over Iran during 1980-2023, which reversed to a decreasing trend in PM, BC and SO around 2006-2010. At the regional scale, aerosols variations were influenced by land-use changes, while urban and agricultural LULC changes being the primary contributors in dust-dominant regions, accounting for 38.1% and 26.4% of the variation, respectively. Our findings indicate that, although land-use changes initially influenced air pollution trends, recent clean-air policies have been essential in reducing emissions across major urban centers. Additionally, these trends in Iran align with or diverge from global patterns, reflecting the rise in industrial emissions across South Asia and contrasting with policy-driven decreases in developed regions such as Europe and North America, highlighting the urgent need for effective policies and land management to mitigate urban air pollution from diverse aerosol sources.