Nanoscale examinations on the sequestration of Cu by organic material in contaminated surface soils in Timmins, Ontario

Abstract

The deposition and alteration of particulate matter (PM) in soils is a world-wide health concern. This study investigates the fate of Copper in organic-rich surficial soil layers (0-5 cm) contaminated by mining related activity at the Timmins Kidd Creek metallurgical site, Canada. The sequestration and mobilization of Cu by organic material (OM) in the soil layer is investigated using focused ion beam (FIB) technology and transmission electron microscopy (TEM). Copper occurs as incidental metallic Cu and covellite (CuS) nanoparticles (NPs), formed via ion reduction by humic substances and magnetite. Additionally, TEM analysis of the colloidal fraction, extracted via ultracentrifugation from the surface soil layer, indicates the occurrence of incidental covellite NPs in close association with dissolved OM. This study shows for the first time that Cu is sequestered as incidental metallic Cu and covellite NPs within OM and magnetite in surficial organic-rich soil layers. Furthermore, the mobility of Cu is facilitated through the transport of covellite nanoparticles embedded within organic colloids.