Bulk and Mapping Speciation Analyses Unveil the Pattern and Heterogeneity of Cu Species during Organic Waste Treatment

• Published in: Environmental science & technology Vol. 58; no. 32; pp. 14439 - 14449
• Main Authors: Doelsch, Emmanuel, Le Bars, Maureen, Etschmann, Barbara, Formentini, Thiago, Legros, Samuel, Levard, Clément, Chaurand, Perrine, Basile-Doelsch, Isabelle, Rose, Jérôme, Brunetti, Gianluca, Doolette, Casey, Howard, Daryl L., Lombi, Enzo
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 13.08.2024; American Chemical Society (ACS)
• Subjects: Aerobic conditions; Agricultural land; Agricultural pollution; Agricultural wastes; Anaerobic conditions; Anaerobic digestion; Anaerobic processes; Anaerobic treatment; Composting; Composts; Copper; Crystallization; Engineering; Environmental Sciences; Environmental Sciences & Ecology; Heterogeneity; nanomaterials; Occurrence, Fate, and Transport of Aquatic and Terrestrial Contaminants; Organic waste treatment; Organic wastes; Oxidation; Pattern analysis; Scale (corrosion); Soil pollution; Speciation; Species; Sulfides; Urban agriculture; Valence; Waste treatment; X-ray absorption spectroscopy; trace element; digestate; quantitative mapping; X-ray absorption spectroscopy; compost; copper sulfide
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.4c02887

Organic wastes (OWs) can be a common source of copper (Cu) contamination of agricultural soils. Here we conducted a comprehensive study of 22 raw and treated OWs sampled at 6 different full-scale OW treatment plants. Bulk XANES analysis findings indicated that the Cu oxidation state was subject to changes throughout the OW treatment process, mostly depending on the anaerobic/aerobic conditions prevailing in each treatment stage. These changes were independent of the OW origin (agricultural, urban or industrial). Cu­(I) prevailed in raw OWs and digestates (88–100%), whereas Cu­(II) dominated in composts (46–100%). Bulk EXAFS analysis confirmed these observations and revealed that Cu­(I) species in raw OWs and digestates consisted mainly of Cu­(I)-sulfide (76–100%), while Cu­(II) species (60–100%) in composts were Cu­(II)-citrate, Cu­(II)-carbonate and amorphous Cu­(II)-phosphate. Interestingly, we observed that anaerobic digestion was conducive to the formation of crystallized Cu­(I)-sulfides at the expense of nanosized and poorly crystalline Cu­(I)-sulfide species, and that the recalcitrant Cu­(I) species in composts was always crystallized Cu­(I)-sulfide. XANES imaging analysis revealed Cu­(II) species present in low proportions (2–4%) that were not detected using bulk XAS analysis in raw OWs and digestates. This demonstrated the potential of XANES imaging for probing minor species in complex matrices.