摘要:

Iron (oxyhydr)oxide nanoparticles (IONPs) are formed in many aquatic and soil systems through nucleation and growth in solution (homogeneous precipitation), and at soil-water interfaces (heterogeneous precipitation). This review summarizes the roles of metal ions, organics, and microbes in the nucleation and growth of IONPs in natural settings. Metal ions can adsorb onto mineral surfaces that act as substrates to modify heterogeneous precipitation processes at soil (mineral/organic)–water interfaces. Further, metal ions could also affect homogeneous precipitation through lattice substitution or surface adsorption onto IONPs. Similarly, organic matter can interfere with heterogeneous IONP formation through adsorbing onto mineral surfaces, and can affect homogeneous IONP formation by complexing with iron ions and adsorbing onto IONP surfaces. Indeed, the physicochemical diversity of mineral surfaces and organic matter properties, especially regarding organic functional groups which have varied complexation and (de)protonation capabilities, can profoundly affect these processes. Microbial influences arise through the production of extracellular polymeric substances (EPS) and the redox modulation of the surrounding environment, which alter electron transfer dynamics and surface reactivity to affect the formation of IONPs. This review provides an integrated view of the roles of metals, organics and microbes in IONP formation, which can not only help in the understanding of the iron cycle, but also the biogeochemical fate of contaminants.

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