Trace element and organic matter mobility impacted by Fe 3 O 4 -nanoparticle surface coating within wetland soil

Abstract : Engineered oxide nanoparticles have appeared as a highly promising tool for soil remediation. However, their behaviour under complex environmental exposures (i.e. in natural soils) remains poorly understood and a relevant issue to complete their risk assessments. Prior using iron oxide nanoparticles in soil remediation scenarios, it is crucial to evaluate their possible role on the release of natural organic matter (NOM) and trace elements (TEs) as a vector of trace elements (TEs) as it could contribute to the contamination of aquifers. This work presents leaching experiments demonstrating the effects of magnetite (i.e. nFe3O4) on TEs and natural organic matter (NOM) transport within an organo-mineral horizon from a natural wetland. nFe3O4 (~10nm) with two different surface compositions (i.e. uncoated and dimercapto-succinic acid (DMSA) coating) were used in the experiments and both forms impacted the mobility of the NOM within the organo-mineral horizon. The mobility of the coated nFe3O4 within the horizon was higher than the uncoated nFe3O4 and impacted differently the mobility of TEs and NOM. TEs mobility within the horizon increased in presence of uncoated nFe3O4 with a transfer of elements into the colloidal fraction. This distinctive transfer might be explained by interactions between the surface of nanoparticles with NOM. We also suggest that some of the different behaviours observed might be due to the destabilization of the DMSA coating, highlighting the critical importance of understanding the aging processes of nanoparticles under environmental exposures to assess the risks associated with their use in environmental situations.