RESUMEN

BACKGROUND: Remediation of heavy metal-contaminated water using phytoremediation with accumulator aquatic plants is a promising low-cost emerging technology that adapts very well to the surrounding ecosystem. For the system to work efficiently, metal-saturated plants must be replaced, producing a potentially toxic amount of biomass that is usually stored dry to reduce its volume. The speciation of the high metal content in this biomass is crucial to define its final destination. This work explores the application of synchrotron-based EDIXS (Energy Dispersive Inelastic X-ray Scattering) to monitor the speciation of copper in regional aquatic plants from a laboratory-scale phytoremediation system. RESULTS: The phytofiltration system utilized Lemna minor L. and Salvinia biloba Raddi species grown under controlled conditions of light and nutrient availability. Both species are known hyperaccumulators of copper and are prevalent in lakes and rivers across South America. The validation of EDIXS was previously carried out by comparing the results of copper standard samples with those obtained by XANES. The findings revealed that both plant species retained copper in chemical complexes exhibiting octahedral coordination with a Cu valence of 2. Notably, differences emerged between the leaves and roots of Lemna minor L., suggesting a more pronounced adsorption of copper in its leaves, a trend that intensified with exposure. In opposite, for Salvinia the differences between leaves and roots suggests the presence of specific protective mechanisms to cope the copper exposure. Surprisingly, no significant dependence on copper concentration of the aqueous media was observed for either species. SIGNIFICANCE AND NOVELTY: These promising results endorse the viability of the proposed methodology in identifying the most effective fate of biomass generated in phytoremediation systems. EDIXS provides a valid tool for performing local copper speciation in aquatic plants with sufficient selectivity to identify subtle differences in various biological tissues. The simplicity of this methodology renders it a valuable tool for advancing our comprehension of metal speciation within waste biomass, thereby holding significant implications for the development of environmental remediation strategies.

Asunto(s)

Biodegradación Ambiental , Biomasa , Cobre , Cobre/química , Cobre/metabolismo , Cobre/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo , Contaminantes Químicos del Agua/química , Araceae/metabolismo , Araceae/química , Filtración

RESUMEN

Energy Dispersive Inelastic X-ray Scattering (EDIXS) is a reliable technique for the discrimination and characterization of local chemical environments. By means of this methodology, the speciation of samples has been attained in a variety of samples and experimental conditions, such as total reflection, grazing incidence, and confocal setups. Until now, due to the requirement of a monochromatic and intense exciting beam, this tool had been applied using exclusively synchrotron radiation sources. We present, for the first time, results of test measurements using EDIXS for chemical characterization implemented in a conventional x-ray tube based laboratory. The results show good discrimination between different iron compounds under study, suggesting the real possibility of rutinary chemical state characterizations of samples by means of EDIXS using a conventional x-ray tube.

RESUMEN

Both X-ray total reflection and X-ray Raman scattering techniques were combined to discriminate chemical environments in depth-profiling studies using an energy dispersive system. This allowed, for the first time, to resolve oxidation state on surface nanolayers with a low-resolution system. Samples of pure Cu and Fe oxidized in tap water and salty water, respectively, were studied in the Brazilian synchrotron facility using monochromatic radiation and an EDS setup. The measurements were carried out in total reflection geometry with incident energy lower and close to the K absorption edge of both elements. The results allowed observing the presence of very thin oxide layers, usually not observable with conventional geometries of irradiation. They also permit the identification of the compound present in a particular depth of the sample with nanometric, or even subnanometric, resolution using a low-resolution system.