Particle morphology and soil properties affect the retention of copper oxide nanoparticles in agricultural soils

The interaction between nanoscale copper oxides (nano-CuOs) and soil matrix significantly affects their fate and transport in soils. This study investigates the retention of nano-CuOs and Cu²⁺ ions in ten typical agricultural soils by employing the Freundlich adsorption model. Retention of nano-CuOs and Cu²⁺ in soils was well fitted by the Freundlich model. The retention parameters (K_D, K_F, and N) followed an order of CuO NTs > CuO NPs > Cu²⁺, highlighting significant impact of nano-CuOs morphology. The K_F and N values of CuO NPs/Cu²⁺ were positively correlated with soil pH and electrical conductivity (EC), but exhibited a weaker correlation for CuO NTs. Soil pH and/or EC could be used to predict K_F and N values of CuO NPs or CuO NTs, with additional clay content should be included for Cu²⁺.The different relationship between retention parameters and soil properties may suggest that CuO NTs retention mainly caused by agglomeration, whereas adsorption and agglomeration were of equal importance to CuO NPs. The amendment of Ca²⁺ at low and medium concentration promoted retention of nano-CuOs in alkaline soils, but reduced at high concentration. These findings provided critical insights into the fate of nano-CuOs in soil environments, with significant implications for environmental risk assessment and soil remediation strategies.