Partitioning of Ag and CeO2 nanoparticles versus Ag and Ce ions in soil suspensions and effect of natural organic matter on CeO2 nanoparticles stability

This study examined the solid-liquid distribution of 14.8-nm Ag and 6.2-nm CeO2 nanoparticles in soil suspensions and compared it to that of Ag+ and Ce3+ ions, to better understand their environmental behaviour and fate. After 24 h incubation, more than 51% or 29% of the spiked amounts of Ag or CeO2 nanoparticles, respectively, can be retrieved in the liquid phase of (re)suspended soils. The Ag or Ce concentration remaining in solution depends on the incubation time and was influenced by soil properties. Significant correlations are obtained between, on the one hand, the relative amounts of Ag or CeO2 nanoparticles in suspension and the soil-pH, CEC, texture, suspended matter, nitrogen, phosphorus, TOC and main and trace elements content on the other hand. The presence of dissolved natural organic matter stabilizes CeO2 nanoparticles in the aqueous phase. In soil suspensions, Ag+ and Ce3+ ions seemingly interact more strongly with soil constituents compared to their nanoparticle counterparts, rendering the Ag and CeO2 nanoparticles to be more stable and potentially bioavailable.