RESUMEN
This study evaluates the potential toxicity of the soils of the Guadiamar Green Corridor (GGC) affected by the Aznalcóllar mine spill (Andalusia, Spain), one of the most important mining accidents in Europe in recent decades. Twenty years after the accident, although the area is considered to be recovered, residual contamination in soils persists, and the bioavailability of some contaminants, such as As, is showing trends of increasing. Therefore, the potential residual toxicity in 84 soil samples was evaluated by bioassays with lettuce (Latuca sativa L.), earthworms (Eisenia andrei) and determining the microbial activity by basal respiration and metabolic quotient. The selected soils sampled along the GGC were divided into 4 types according to their physicochemical properties. In the closest part of the mine two soil types appear (SS1 and SS2), originally decarbonated and loamy, with a reduction in lettuce root elongation of 57% and 34% compared to the control, as well as a the highest metabolic quotient (23.9 and 18.1 ng CcO2 µg Cmicrob-1 h-1, respectively) with the highest risk of Pb and As toxicity. While, located in the middle and final part of the affected area of the spill (SS3 and SS4), soils presented alkaline pH, finer textures and the lowest metabolic quotient (<9.5 ng CcO2 µg Cmicrob-1 h-1). In addition, due to Pb and As exceeded the Guideline values established in the studied area, the human toxicity risk was determined according to US-EPA methodology. Although the total contents were higher than the Guidelines established, the obtained hazard quotients for both contaminants were less than one, so the risk for human health was discarded. However, monitoring over time of the toxicity risks of the GGC soils would be advisable, especially due to the existence of areas where residual contamination persist, and soil hazard quotient obtained for As in children was higher and close to unity.
Asunto(s)
Metales Pesados , Contaminantes del Suelo , Niño , Humanos , Suelo/química , Plomo , Metales Pesados/análisis , Contaminantes del Suelo/análisis , Monitoreo del Ambiente , Medición de RiesgoRESUMEN
Brushite is a biocompatible calcium phosphate mineral with properties of solid electrolyte. In this study we take advantage of this characteristic to develop an enzymatic amperometric biosensor based on brushite cement. The biosensor was prepared by immobilizing tyrosinase (PPO) on a brushite cement layer which was subsequently cross-linked with glutaraldehyde (GA) on the surface of a glassy carbon electrode. The system was optimized for the detection of phenolic compounds in both aqueous and non-aqueous solutions. Several variables involved in the enzyme immobilization method such as glutaraldehyde cross-linking time, PPO/brushite ratio and thickness of the brushite film were investigated. Furthermore, the effects of the pH, temperature and applied potential on the biosensor performance were also optimized. On the other hand, the biosensor analytical properties were studied in presence of different organic solvents: dioxane, acetonitrile and ethanol. In both, phosphate buffer solution (PBS) and acetonitrile/PBS solution, the biosensor exhibits a rapid response (12 s); a wide linear range (0.001-3 microM and 0.007-2 microM respectively); low detection limit (1 and 2 nM respectively); and high sensitivity (46.6 and 28.6 A M(-1) cm(-2) respectively). The performance of the biosensor in the analysis of phenols in real samples was successful.
Asunto(s)
Materiales Biocompatibles/química , Técnicas Biosensibles/instrumentación , Cementos para Huesos/química , Fosfatos de Calcio/química , Electroquímica/instrumentación , Fenoles/análisis , Diseño de Equipo , Análisis de Falla de Equipo , Fenoles/química , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
An amperometric enzyme sensor using tyrosinase (PPO) entrapped in polyacrylamide microgels has been developed for determination of phenolic compounds. Polyacrylamide microgels were obtained by the concentrated emulsion polymerization method. The crosslinking of the polymer matrix optimum to retain the enzyme and to allow the diffusion of the compounds involved in the enzyme reaction has been studied (4.0%) as well as the influence on the response of analytical parameters such as pH, temperature, enzyme load and working potential. The useful lifetime of the biosensor was 27 days and it was useful to determine monophenolics compounds (e.g. cresol, chlorophenol) and diphenolics compounds (e.g. catechol and dopamine) by amperometric measurements at -100mV (versus SCE) in a batch system. The results showed that the substrate structures have a great influence on the sensor response.
Asunto(s)
Resinas Acrílicas/química , Técnicas Biosensibles/instrumentación , Electroquímica/instrumentación , Monofenol Monooxigenasa/química , Fenoles/análisis , Técnicas Biosensibles/métodos , Electroquímica/métodos , Enzimas Inmovilizadas/química , Diseño de Equipo , Análisis de Falla de Equipo , Tamaño de la Partícula , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Acrylic microgels are proposed as enzyme immobilizing support in amperometric biosensors. Two enzymes, glucose oxidase and tyrosinase, were entrapped in this matrix and their behaviour is compared. The optimum cross-linking of the polymeric matrix required to retain the enzyme, and to allow the diffusion of the substrate is different for each enzyme, 3.2% for glucose oxidase and 4.5% for tyrosinase. The effect of pH and temperature on the biosensor responses has been studied by experimental design methodology and predictions have been compared with independently performed experimental measurements. A quadratic effect of the variables studied (pH and T) on the biosensor response and the small or null interaction between them was confirmed. The pH results obtained with both methods are coincident revealing an reversible effect on the enzyme. However, the temperature optimum value obtained by experimental design was 10 degrees C lower as a result of an activity decay due to irreversible thermal denaturation of both enzymes.