Assessing the Impact of Iron-based Nanoparticles on pH, Dissolved Organic Carbon, and Nutrient Availability in Soils

With the ongoing commercialization of nanotechnology products, the increasing use of engineered nanoparticles (NPs) could lead potentially to environmental risks. This study investigated the dynamic influences of three iron-based NPs (Fe-0, Fe3O4, and Fe2O3) applied into a red soil (RS) and a Wushan soil (WS) with different application rates (2 to 6 g kg(-1)) on soil physicochemical properties such as pH, dissolved organic carbon (DOC), available ammonium nitrogen (NH4+-N), available phosphorus (AP), and enzymatic activities. The results showed that the addition of Fe-0 NPs increased DOC and available NH4+-N, but significantly decreased AP, while Fe3O4 and Fe2O3 NPs slightly reduced soil pH in both soils and significantly declined available NH4+-N in the WS and AP in the RS. No significant difference was observed between the effects of Fe3O4 and Fe2O3 NPs on soil properties except AP in the RS. All iron-based NPs decreased the activities of urease and acid phosphatase in both soils. The effects on soil physicochemical properties, especially available NH4+-N and AP induced by iron-based NPs, varied greatly with soil types. These results implied that cautions should be paid for the environmental application of iron-based NPs, especially iron oxide NPs in soils.