With the rapid development of nanotechnology, the environmental behavior and ecological effect of nanoparticles (NPs) are receiving more and more attention. As an important environmental component, metal oxide NPs occur widely in nature, such as in water bodies, air, soils, and sediments. They have a large surface area and high surface activity, allowing them to control and affect the speciation, migration, transformation, and bioavailability of some contaminants and nutrients in the environment. The nano-size is a unique property of nanoparticles. The size of particles regulates and determines the structure and physicochemical properties of nano-oxides, which greatly affects interfacial reactions with the relevant elements and environmental geochemical behaviors. The effects of NPs size on the environmental geochemical behaviors, such as adsorption, (reductive) dissolution, (catalytic) oxidation, aggregation and transport, are briefly summarized, and the mechanism of the size effect is discussed. Finally, hot spots for future research of metal oxide nanoparticles related to size effects in the environment are proposed.
Keywords: adsorption; aggregation; catalytic; dissolution; environmental behaviors; metal oxide; nanoparticles; size effect; transport.