This study was conducted to provide a quantitative assessment of the relative contribution of active dust sources in Qom Province—specifically Cheshmeh Shur and Namak Lake—to the transport and accumulation of particulate matter (PM₁₀) in Alborz Province, Iran. The issue is of particular relevance because, in recent decades, dust storms have emerged as a critical environmental hazard across the Middle East, with significant implications for public health, infrastructure, and climate systems. Qom Province, due to its central location, arid to semi‑arid climate, steadily declining vegetation cover, and expansive areas of exposed soil, is recognized as one of the most important domestic sources of dust emissions in the country. The proximity of Qom to Alborz Province, combined with prevailing southeasterly wind patterns during peak dust seasons, creates favorable conditions for inter‑provincial dust transport, particularly toward densely populated urban centers such as Karaj and Fardis.



To quantify the specific influence of these sources, this research employed a numerical modeling approach using the Weather Research and Forecasting model coupled with the Chemistry module (WRF‑Chem, version 4.2), integrated with the GOCART Dust emission scheme. This coupled modeling system allows for the simultaneous simulation of meteorological fields and dust particle dynamics, providing a physically consistent framework to investigate emission–transport–deposition processes. The study period spanned 2014 to 2024, ensuring the inclusion of interannual variability in dust activity.



Within this decade‑long interval, 19 high‑intensity dust events were selected for detailed simulation. Selection criteria were based on objective observational thresholds—PM₁₀ concentrations exceeding 200 µg/m³, documented visibility reductions below three kilometers, corresponding wind directions from the south or southeast, and independent confirmation from satellite‑based aerosol and dust imagery (e.g., MODIS, Sentinel‑2). This ensured that the modeled events were representative of major episodes affecting air quality in Alborz Province and linked to potential emissions from Qom’s key dust‑active surfaces.



The core experimental design involved two separate but otherwise identical model runs. The baseline scenario included all natural dust emission sources as defined in the regional emission inventory, including Cheshmeh Shur and Namak Lake in Qom. The removal scenario artificially suppressed emissions from these two sources in the model input files, effectively isolating their contribution to PM₁₀ concentrations in downwind regions. This “source apportionment by removal” approach, while computationally intensive, is widely regarded as one of the most robust methods for quantifying individual source impacts in atmospheric modeling studies.



Model performance was rigorously evaluated using ground observations from the Alborz air quality monitoring network. Statistical validation metrics included the Root Mean Square Error (RMSE) to measure average prediction errors, the Pearson correlation coefficient ® to assess temporal co‑variability between observations and simulations, and the Index of Agreement (IOA) to evaluate the overall match in magnitude and phase. The model exhibited strong skill in simulating observed PM₁₀ patterns, with R = 0.81 across all events, confirming its suitability for the attribution analysis.



The results demonstrated that suppressing Qom dust emissions in the model led to an average decrease of 11.23% in PM₁₀ concentrations across Alborz Province during the simulated events. The reductions were not uniform in time or space: extreme events showed decreases exceeding 30%, and spatial mapping revealed that the greatest impacts occurred along the prevailing southeasterly wind corridor toward Karaj and Fardis—the principal population and industrial centers. Temporal breakdowns indicated that the largest scenario differences coincided with peak dust storm hours, especially in the late afternoon to early evening, when boundary‑layer mixing and dust transport conditions are most favorable.



These findings provide compelling quantitative evidence that domestic dust sources in Qom play a significant, and in some cases dominant, role in degrading air quality in Alborz Province during dust storm episodes. This has several important policy and management implications. First, it suggests that air quality improvement strategies for Alborz cannot rely solely on controlling local emissions (e.g., traffic, industrial activities) but must incorporate regionally coordinated dust mitigation measures targeting upwind provinces. Second, land management interventions in Qom—such as surface stabilization, restoration of vegetation cover, and optimized water resource management to prevent further desiccation of Cheshmeh Shur and Namak Lake—could have measurable benefits for air quality in multiple downwind regions. Third, the modeling framework demonstrated here can be adapted for scenario testing of future climate or land‑use change impacts, supporting evidence‑based planning.



Furthermore, the study’s methodological approach aligns with best practices in regional dust modeling by combining observationally validated numerical simulations with emission source manipulation. This ensures that the findings are not only statistically robust but also physically interpretable in terms of emission–transport dynamics. The decade‑long study window adds resilience to the conclusions by capturing a range of meteorological and land surface variability, reducing the chance that results are biased by atypical single‑year conditions.



In summary, the research underscores the strategic importance of controlling domestic dust sources—specifically in Qom Province—not only for local environmental health but for the protection of downwind urban areas. The quantitative attribution achieved here provides a valuable scientific foundation for integrated air quality management, cross‑provincial environmental policymaking, and the development of operational early warning systems for dust events in densely populated areas such as Karaj.



Keywords: Alborz Province, Dust storm, PM₁₀, Qom Province, WRF‑Chem, GOCART Dust, source apportionment, environmental policy.