Mineralogical Investigation of Riverine Suspended Particulate Matter: A Comprehensive Review of Sampling, Characterization and Analytical Techniques

Suspended particulate matter (SPM) governs the transport of sediments, nutrients, trace elements, radionuclides, and organic contaminants in water bodies, largely through its mineral fraction, which controls contaminant mobility and bioavailability. Characterizing this fraction remains challenging because of small particle size, complex organo-mineral associations, poor crystallinity, and the dynamic nature of aquatic particles. This review critically compares the principal sampling strategies and analytical techniques available for investigating the mineral fraction of riverine SPM, from bulk approaches (specific surface area, elemental and mineralogical analyses) to particle- and atomic-scale methods (manual and automated electron microscopy, X-ray absorption spectroscopy, isotopic analyses). For each technique, we synthesize the information it provides, its sample-preparation constraints and artefacts, and its complementarity with other methods, summarized in a comparative table. We show that no single technique is sufficient to characterize natural SPM. Only the integration of complementary methods across spatial scales provides a robust framework for understanding particle composition, reactivity, and contaminant dynamics. We further highlight emerging opportunities offered by in-situ and autonomous sampling technologies, cryogenic and in-situ electron microscopy, and machine-learning-based multimodal data fusion. Future progress will depend on harmonized sampling and analytical protocols, international SPM databases, and combined laboratory-field approaches.