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

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.

Multivariate regression analysis of factors regulating the formation of synthetic aluminosilicate nanoparticles.

Interest is growing in nanoparticles made of earth abundant materials, like alumino(silicate) minerals. Their applications are expanding to include catalysis, carbon sequestration reactions, and medical applications. It remains unclear, however, what factors control their formation and abundance during laboratory synthesis or on a larger industrial scale. This work investigates the complex system of physicochemical conditions that influence the formation of nanosized alumino(silicate) minerals. Samples were synthesized and analyzed by powder X-ray diffraction, in situ and ex situ small angle X-ray scattering, and transmission electron microscopy. Regression analyses combined with linear combination fitting of powder diffraction patterns was used to model the influence of different synthesis conditions including concentration, hydrolysis ratio and rate, and Al : Si elemental ratio on the particle size of the initial precipitate and on the phase abundances of the final products. These models show that hydrolysis ratio has the strongest control on the overall phase composition, while the starting reagent concentration also plays a vital role. For imogolite nanotubes, we determine that increasing concentration, and relatively high or low hydrolysis limit nanotube production. A strong relationship is also observed between the distribution of nanostructured phases and the size of precursor particles. The confidences were >99% for all linear regression models and explained up to 85% of the data variance in the case of imogolite. Additionally, the models consistently predict resulting data from other experimental studies. These results demonstrate the use of an approach to understand complex chemical systems with competing influences and provide insight into the formation of several nanosized alumino(silicate) phases.

Hyper-accumulation of vanadium in animals: Two sponges compete with urochordates.

Vanadium (V) concentrations in organisms are usually very low. To date, among animals, only some urochordate and annelid species contain very high levels of V in their tissues. A new case of hyper-accumulation of V in a distinct animal phylum (Porifera), namely, the two homoscleromorph sponge species Oscarella lobularis and O. tuberculata is reported. The measured concentrations (up to 30 g/kg dry weight) exceed those reported previously and are not found in all sponge classes. In both Oscarella species, V is mainly accumulated in the surface tissues, and in mesohylar cells, as V(IV), before being partly reduced to V(III) in the deeper tissues. Candidate genes from Bacteria and sponges have been identified as possibly being involved in the metabolism of V. This finding provides clues for the development of bioremediation strategies in marine ecosystems and/or bioinspired processes to recycle this critical metal.