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, Fe 3 O 4, and Fe 2O 3) 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 (NH 4 +-N), available phosphorus (AP), and enzymatic activities. The results showed that the addition of Fe 0 NPs increased DOC and available NH 4 +-N, but significantly decreased AP, while Fe 3O 4 and Fe 2O 3 NPs slightly reduced soil pH in both soils and significantly declined available NH 4 +-N in the WS and AP in the RS. No significant difference was observed between the effects of Fe 3O 4 and Fe 2O 3 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 NH 4 +-N and AP induced by ironbased 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