The study of the formation and occurrence of metal(loid)-bearing nanoparticles in organic-rich colloids and particles within contaminated surficial soils in Rouyn Noranda, Quebec
MetadataShow full item record
Contamination of soils through deposition and alteration of metal(loid)-bearing particulate matter (PM) is a global problem. This study investigates the fate of Copper (Cu) in oxic organic-rich soil layers contaminated by mining and smelting operations around the Horne smelter, Rouyn Noranda, Quebec, Canada. The sequestration of Cu by organic colloids and particles is investigated by using column leaching experiments, ultra-centrifugation, focused ion beam technology (FIB), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT). Cu occurs as nano-sized Cu-sulfides (CuSx) phases within the matrix of micrometer-sized organic colloids and as nano-sized spinel phases such as Cu-Zn-bearing magnetite (Fe3O4) or nano-sized Cu-(hydr)oxides such as cuprite (Cu2O) and spertiniite (Cu(OH)2) within pre-mineralized organic matter (OM). The formation of these Cu-bearing NP is controlled by the porosity and occurrence of silicate phases, which mineralize the OM in multiple stages. Based on these observations models are developed for the sequestration of Cu by organic colloids and particles. The models include proposed mechanisms for (a) mineralization of OM, adsorption and distribution of ionic Cu-species and (b) nucleation and stabilization of nano-sized CuSx, Cu-bearing spinels and Fe-(hydr)oxide phases. Here, diffusion of Cu and other metal(loid) species is promoted by the generation of porosity and nucleation of silicates during the mineralization of organic colloids and particles. Nucleation and formation of Cu-and Fe-bearing nanoparticles are promoted by the presence of hydrophilic silicate surfaces (which promote heterogeneous nucleation) and nanopores generated due to hydrodynamic properties of pore channels (which control the availability of metal(loid) species and pore size-controlled solubility effects (PCS). The characterization of OM with APT allowed for the first time the visualization of clusters of polymerized CuOx polyhedra in smaller pore spaces of the OM. These clusters are considered precursors of nanoparticles and their occurrence in smaller pore spaces suggests that pore size and PCS strongly control the formation of Cu-bearing nanoparticles within OM.