Copper speciation mapping of organic wastes using XANES imaging

Copper (Cu) is potentially toxic trace elements present in large amounts in organic wastes (OWs) spread on agricultural lands as fertilizer. Cu speciation in OW is a crucial parameter to understand their fate in soil after spreading and to assess the risk associated with agricultural recycling of OW. To explore the spatial heterogeneity of Cu species at the µm scale from raw OWs up to digestates and composts, we used a laterally resolved synchrotron techniques, the so-called fluorescence-XANES imaging approach. For each organic wastes, an initial large area survey scan at 15.8 keV has been conducted to identify the area of interest and obtain overall elemental distributions. Subsequently, a smaller area has been chosen to conduct fluorescence XANES imaging with the XANES stack itself consisting of individual maps at decreasing energies across the Cu K-edge. These analyses have been conducted for 7 organic wastes: Urban-3_Raw_OW Urban-3_Compost Agri-1_Raw_OW Agri-1_Digestate Agri-1_Compost Central-1_Raw_OW Central-1_Digestate