Fitorremediación con Brassicaceae y Apiaceae en suelos contaminados con metales pesados

Introducción: La cuenca media del río Bogotá viene sufriendo contaminación por metales pesados debido a los vertidos industriales. Esta fuente de agua ha sido utilizada para el riego de cultivos de ciclo corto, lo que ha provocado la contaminación por metales pesados de los suelos productivos. Objetivo: Evaluar un proceso de fitorremediación con las especies de Brócoli (Brassica oleracea var. italica Plenck) y Cilantro (Coriandrum sativum L.) en suelos contaminados con metales pesados en Mosquera, Colombia. Métodos: El muestreo se realizó con un diseño factorial al azar: a) proporciones de cilantro/brócoli (30 cilantro/70 brócoli, 50/50, 70 cilantro/30 brócoli y dos controles de tipo monocultivo de cada especie) y b) tiempo de fitorremediación (3, 6 y 9 meses), cada tratamiento con cuatro parcelas experimentales. El suelo y el tejido vegetal se analizó mediante espectrofotometría de absorción atómica para determinar la concentración de los metales pesados. Resultados: Las concentraciones de metales pesados en las muestras de tejido vegetal para brócoli y cilantro mostraron valores de Cd, Pb y Cr más altos que Hg y As, respecto al control. Las concentraciones de Cd, Pb y Cr presentaron valores significativamente más altos (P < 0.05) en suelos con cilantro y brócoli mezclados, respecto al sitio de control donde la concentración de Cd registró niveles significativamente más bajos que en los otros suelos. Las concentraciones de Cd, Pb y Cr fueron más altas en tejidos de cilantro y en suelos con cilantro en comparación con el control. Conclusiones: La fitorremediación por medio de las especies Brassica oleracea var. itálica Plenck y Coriandrum sativum L. en proporciones 70/30 o 30/70 a suelos con pH entre 5.5 y 6.0 permiten una buena recuperación de suelos con contenidos de metales pesados en términos de concentraciones altas a cortos plazos, iniciando la biorremediación a los tres meses y finalizando cargas de disponibilidad variable a los nueve meses.

Introduction: The middle basin of the Bogotá River has been suffering from heavy metal contamination due to industrial discharges. This water source has been used to irrigate short-cycle crops, which has resulted in heavy metal contamination of productive soils. Objective: To evaluate a phytoremediation process with the plant species Broccoli (Brassica oleracea var. Italica plenck) and Cilantro (Coriandrum sativum L.) in soils contaminated with heavy metals in Mosquera, Colombia. Methods: Sampling was performed with a randomized factorial design: a) cilantro/broccoli proportions (30 cilantro/70 broccoli, 50/50, 70 cilantro/30 broccoli and two monoculture type controls of each species) and b) phytoremediation time (3, 6 and 9 months), each treatment with four experimental plots. Soil and plant tissue were analyzed in the laboratory by atomic absorption spectrophotometry to determine the concentration of heavy metals. Results: The concentrations of heavy metals in plant tissue samples for broccoli and cilantro showed higher values of Cd, Pb and Cr than Hg and As, with respect to the control. The concentrations of Cd, Pb and Cr presented significantly higher values (P < 0.05) in soil where there was a mixed presence of cilantro and broccoli, with respect to the control site where the concentration of Cd registered significantly lower levels than in the other soils. Finally, Cd, Pb and Cr concentrations were higher in cilantro tissues and in soils with cilantro compared to the control. Conclusions: Phytoremediation by means of Brassica oleracea var. italica Plenck and Coriandrum sativum L. in 70/30 or 30/70 proportions in soils with pH between 5.5 and 6.0 allows a good recovery of soils with heavy metal contents in terms of high concentrations in short terms, starting bioremediation after three months and ending loads of variable availability after nine months.

Hybrid materials based on chitosan functionalized with green synthesized copper nanoparticles: Physico-chemical and antimicrobial analysis.

Recently, the development of materials with antimicrobial properties has become a challenge under scrutiny. The incorporation of copper nanoparticles (NpCu) into a chitosan matrix appears to represent a viable strategy to contain the particles and prevent their oxidation. Regarding the physical properties, the nanocomposite films (CHCu) showed a decrease in the elongation at break (5 %) and an increase in the tensile strength of 10 % concerning chitosan films (control). They also showed solubility values lower than 5 % while the swelling diminished by 50 %, on average. The dynamical mechanical analysis (DMA) of nanocomposites revealed two thermal events located at 113° and 178 °C, which matched the glass transitions of the CH-enriched phase and nanoparticles-enriched phase, respectively. In addition, the thermogravimetric analysis (TGA) detected a greater stability of the nanocomposites. Chitosan films and the NpCu-loaded nanocomposites demonstrated excellent antibacterial capacity against Gram-negative and Gram-positive bacteria, proved through diffusion disc, zeta potential, and ATR-FTIR techniques. Additionally, the penetration of individual NpCu particles into bacterial cells and the leakage of cell content were verified by TEM. The mechanism of the antibacterial activity of the nanocomposites involved the interaction of chitosan with the bacterial outer membrane or cell wall and the diffusion of the NpCu through the cells. These materials could be applied in diverse fields of biology, medicine, or food packaging.

Chitosan-based nanocomposite matrices: Development and characterization.

Chitosan-based nanocomposites have a significant industrial impact related to the possibility to design and create new materials and structures. Cellulose nanocrystals (CNC) can be extracted from microcrystalline cellulose (MCC) by controlled acid hydrolysis with H2SO4. This work was focused on: to study the microstructure of CNC isolated from MCC after different hydrolysis times; to develop nanocomposites chitosan-based films; to characterize their structural and thermo-mechanical properties; to analyze the spectral differences among samples by means of ATR-FTIR in combination with principal component analysis (PCA) and square partial minimums model (PLS). It is worth noting that the selected condition for isolate the CNC from MCC was the acid treatment for 2 h, evidenced by size measurements. This fact was supported by transmission electron microscope (TEM) and dynamic light scattering (DLS). In this regard, SEM studies of films showed an assembly process between the nanocelluloses and the CH matrix. The incorporation of CNC into the films resulted in strong interactions between the filler and the matrix demonstrating the affinity between the phases and modifying the mechanical profiles. In summary, CNC was found to be a satisfactory reinforcing agent in biodegradable nanocomposite chitosan-based packaging and are promising as a means to develop tailor-made materials.