Multi-scale mechanisms and environmental implications of dissolved organic matter-metal ions interactions in aquatic...

The binding interactions between metal ions and dissolved organic matter (DOM) are ubiquitous in freshwater/marine aquatic environments where both coexist. Distinct from free metal ions or DOM, DOM-metal ions (DOM-Me) complexes have emerged as contaminants of emerging concern, primarily due to their altered physicochemical properties, modified migration and transformation patterns, enhanced environmental persistence, and changed ecotoxicity. However, based on the multi-source heterogeneity of DOM and the diversity of metal ions, systematic investigations into the interaction mechanisms and environmental implications of DOM-Me complexes in water environments remain scarce. Therefore, this review critically evaluates the emerging separation and detection methods for homogeneous DOM-Me complexes-fundamental for understanding their interaction mechanisms. Further, the interaction mechanisms of DOM-Me complexes, dynamic regulation by environmental factors, and environmental ecological toxicological effects are systematically analyzed across multi-scale perspectives (molecular, meso-, and macro-scales). Simultaneously, various combined fitting models are objectively assessed. By integrating reasonable assumptions, theoretical knowledge, and findings from prior studies, a few future research directions and suggestions are proposed. These efforts aim to support the advancement of systematic research on DOM-Me complexes and provide references for optimizing subsequent treatment processes and ecological environment restoration.