A method for determination of retention of silver and cerium oxide manufactured nanoparticles in soils

Methods to study the retention of manufactured nanoparticles (MNP) are lacking for soils that are likely to be increasingly exposed to MNP. In this study we present, for the first time, a method to determine retention values (K-r) of Ag and CeO2 MNP, that can be ranked among solid-liquid partitioning (K-d) values of bulk (micrometre-sized) forms, soluble salts and other possible contaminants of soils. After method optimisation, suspensions containing 1.24 mg kg(-1) Ag as Ag MNP and 1.30 mg kg(-1) Ce as CeO2 MNP were added to five soils. More than 7% of Ag MNP occurred as soluble Ag-I after 24 h and the range of K-r values of Ag MNP (77-2165 L kg(-1)) and CeO2 MNP(1.1-2828 L kg(-1)) contrasted with K-d values of soluble Ag-I, Ce-III and Ce-IV salts and bulk Ag and CeO2 powders in different soils.