Partitioning of manufactured Ag and CeO2 nanoparticles in relation to soil properties

Abstract

Soils are likely to be increasingly exposed to manufactured nanoparticles (MNP), but a better understanding of the influence of soil properties on their fate can improve risk assessment. The solid-liquid partitioning (Kd) and dissolution of silver (Ag) MNP and cerium oxide (CeO2) MNP was determined after spiking soils of varying properties and compared with soluble Ag(I), Ce(III), and Ce(IV) and bulk Ag(0) and bulk CeO2(s). In addition, MNP Kd values were determined in the same soils made sodic, after the addition of biosolids, or with increased chloride and phosphate concentrations. Kd values for MNP were mostly not significantly different than for soluble analogues but were much lower than for bulk powders. High clay content was suggested to increase Kd MNP, and especially in the presence of high Cl concentrations, 39% of added Ag MNP was dissolved. The presence of phosphate in soil suspensions decreased the Kd values in clayey soils from values higher than 10000 to values lower than 30 for CeO2 MNP that appeared to dissolve much less than Ag MNP. The fate of Ag MNP and CeO2 MNP in soils thus appears to be determined by more factors than have to date been investigated.