Abstract
Particulate materials, from macroparticles to colloids and nanoparticles, might be critical regulators of geochemical cycles in aquatic environments. However, their behaviors are profoundly dictated by surrounding physicochemical conditions in freshwater or marine systems. This review systematically synthesizes current knowledge by providing a comparative analysis of particle dynamics across this environmental boundary, with a specific emphasis on the distinct roles of nanoparticles (1–100 nm). We first compare the sources and composition of particles, highlighting the dominance of terrigenous inputs in freshwater versus biogenic sources in marine environment. Subsequently, we critically evaluate analytical methods, revealing how matrix-specific properties (e.g., salinity) create distinct challenges for accurate characterization. The review demonstrates that nanoparticles, due to their high reactivity, act as dynamic drivers of elemental cycling and contaminant fate. A case study on deep-sea hydrothermal vents illustrates this, revealing how nanoparticles facilitate the long-range transport of micronutrients like iron, overturning previous paradigms of localized impact. By highlighting these freshwater-marine disparities and trying to identify critical knowledge gaps in analytical methods and transformation mechanisms, this review provides an integrated framework and outlines priority directions for future research.