Geochemical linkage between desiccated lakebed sediments and airborne particulate matter in the Lake Urmia basin, northwestern Iran.

This study investigates airborne particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5) provenance in the Lake Urmia basin, northwestern Iran, by coupling dust geochemistry with the composition of desiccated hypersaline lake sediments. PM2.5 was simultaneously collected from two cities of Urmia (URM) and Tabriz (TBR) during 9 months period in 2024, while surface sediments were sampled from exposed Lake Urmia Sediments (LUS). Elemental concentrations, diagnostic elemental ratios, Parker Weathering Index (PWI), Upper Continental Crust (UCC)-normalized Rare Earth Element (REE) patterns, ternary diagrams, and Pearson correlation analysis were integrated within a multi-proxy geochemical framework. Evidence consistently indicates that PM2.5 collected in TBR exhibits a strong geochemical affinity with LUS. This relationship is reflected by overlapping elemental concentration ranges, parallel Light Rare Earth Element (LREE)-enriched UCC-normalized REE patterns, coherent clustering in REE ternary diagrams, and highly correlated elemental pairs between TBR and LUS. These patterns are further supported by significant correlations between PWI and diagnostic elemental ratios across both TBR and LUS. In contrast, PM2.5 from URM displays weaker elemental coherence, fewer strong correlations, and partial negative associations. Despite its greater distance from the lake, the stronger influence of Lake Urmia on TBR particulate matter is physically consistent with prevailing southwest to northeasterly wind regimes and regional transport pathways. Comparison with other drying terminal lakes, including the global analogs, suggests that the contribution of lacustrine-derived materials to PM2.5 in TBR is exceptionally high, driven by extreme lake desiccation and favorable wind alignment. These findings demonstrate that Lake Urmia has transitioned from a hydrologically confined basin to an atmospherically dominant dust source.