Beyond Traditional Source Apportionment: A Three-Dimensional Approach to Unravel PM₁₀ Sources, Composition, and Transport Pathways

Atmospheric aerosols originate from a complex interplay of local emissions, secondary formation processes, and regional-to-long-range transport, making source identification a major challenge for air quality and climate research. Traditional investigations often rely on a single analytical approach, which often falls short in resolving this complexity, leaving critical gaps in our understanding of aerosol origin, composition, and transport. This study argues and demonstrates the power of integrating a three-dimensional approach that combines chemical mass closure, receptor modelling, and atmospheric transport analysis to achieve a more comprehensive understanding of aerosol sources. Applied to a year-long PM₁₀ dataset collected in Tetouan, northern Morocco, the combination of Positive Matrix Factorization (PMF), chemical mass closure, and Concentration Weighted Trajectory (CWT) analysis enabled a multi-dimensional characterization that no single method could deliver alone. PMF resolved four distinct source profiles, including vehicle exhaust, secondary inorganic aerosols, fresh sea salt, and nitrate–biomass burning, while chemical mass closure quantified the relative abundance of key aerosol components, with mineral dust, particulate organic matter, and water-soluble inorganic ions dominating the PM₁₀ mass. CWT analysis then extended the picture geographically, tracing emission origins across the Mediterranean Basin, southern Europe, and the Atlantic Ocean, and linking transport pathways to observed chemical signatures. The results demonstrate that each method independently captures a partial picture, but their integration reveals connections between source types, seasonal dynamics, and geographical origins that would otherwise remain invisible. This work makes the case that multi-method frameworks are not merely complementary but are arguably essential for robust source apportionment. The proposed approach offers a transferable methodology for aerosol studies in complex environments where local emissions interact with regional atmospheric transport and secondary aerosol formation processes.