Efecto de la aplicación de biosólidos sobre la calidad del suelo: evolución temporal de suelo degradado, Región de La Araucanía, Chile

En suelo Inceptisol de la región de la Araucanía, de condición degradado, se determinó la evolución temporal en propiedades del suelo posterior a un evento de aplicación de biosólido. En el sitio de estudio se establecieron dos zonas de muestreo: zona sin aplicación de biosólidos y zona con aplicación de biosólidos, evaluándose parámetros químicos, físicos y biológicos a los 17, 210, 365 y 510 días de aplicado el biosólido. Los resultados muestran cambios relevantes en la calidad de suelo trascurridos 1.4 años desde la aplicación, particularmente en relación al aumento sostenido en el contenido de fósforo, respiración edáfica e infiltración

Simplification in the use of macroinvertebrates in the evaluation of water quality in fluvial systems

Macroinvertebrates have been used for decades to evaluate water quality, using measures of diversity, biotic indexes and comparative analysis. The taxonomic level of family allows a general interpretation of the ecological quality of a fluvial system, and is possible to infer the quality of these systems compared to selected references sites. This paper analyzed three localities of Central-South Chile by means of grouping analysis, evaluating if there is any loss of information when using two hierarchic levels. It is shown that the family level of benthic macroinvertebrates is sufficient for environmental monitoring. The practical advantages, the integrating capacity that can be reached and its relation with environmental variables are discussed.Los macroinvertebrados han sido utilizados por décadas para evaluar la calidad de las aguas, utilizando medidas de diversidad, índices bióticos y comparativos, sugiriendo que el nivel taxonómico de familia permite una buena interpretación general de la calidad ecológica de un sistema fluvial y es posible hacer inferencias sobre la calidad de éstos sistemas respecto a condiciones de referencias seleccionadas. Este trabajo analiza independientemente tres localidades de Chile centro-sur, mediante un análisis de agrupación, evaluando si existe pérdida de información al utilizar dos niveles jerárquicos, destacando que el nivel de familias en macroinvertebrados bentónicos es suficiente para la realización de monitoreos ambientales. Se discuten las ventajas prácticas, la capacidad integradora que puede alcanzarse y su relación con las variables ambientales

Modelado y simulacion de un biofiltro para el tratamiento de gases contaminados con compuestos sulfurados

A mathematical model and the simulation of a biofilter for the treatment of gaseous effluents are presented. The mixture included sulfur compounds such as hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfide, all dissolved in air. The conditions under which restrictions on diffusion are of less importance than biodegradation, which is the ultimate limiting factor, were determined. The model was applied to the biofilm and the results were used to simulate the behavior of the bioreactor. The flows and maximum concentrations of contaminants in the mixture to be treated for a given size of bioreactor, were determined. Also, the concentration-related variations in the efficiency of the removal of contaminants under varying conditions of flow and concentration in the mixture, were established. It was found that biodegradation in the biofilm was the limiting factor for mixtures with concentrations of contaminants greater than 90 ppm

Mesoscale Characterization of Fracture Properties of Steel Fiber-Reinforced Concrete Using a Lattice–Particle Model

This work presents a lattice–particle model for the analysis of steel fiber-reinforced concrete (SFRC). In this approach, fibers are explicitly modeled and connected to the concrete matrix lattice via interface elements. The interface behavior was calibrated by means of pullout tests and a range for the bond properties is proposed. The model was validated with analytical and experimental results under uniaxial tension and compression, demonstrating the ability of the model to correctly describe the effect of fiber volume fraction and distribution on fracture properties of SFRC. The lattice–particle model was integrated into a hierarchical homogenization-based scheme in which macroscopic material parameters are obtained from mesoscale simulations. Moreover, a representative volume element (RVE) analysis was carried out and the results shows that such an RVE does exist in the post-peak regime and until localization takes place. Finally, the multiscale upscaling strategy was successfully validated with three-point bending tests.Ministerio de Economía y Competitividad BIA2013-48352-

Implicancias ambientales de la deslignificación de pulpas kraft de eucalipto utilizando perácidos

Because of great environmental pressures, the cellulose industry has studied the potential of use of new bleaching agents among which peroxymonosulfuric acid and peracetic acid stand out. This survey summarizes the results of various laboratory investigations using peracids to delignify eucalyptus kraft pulps. The effect of a step using peroxymonosulfuric acid followed by a D-Eo-D sequence [free of elemental chlorine] was studied and compared with the use of peracetic acid and mixtures of these two acids. It was shown that a mixture of peroxymonosulfuric acid and peracetic acid reduced more lignin (measured as kappa index) than the individual peracids, and reduced more hexenuronic acid than peracetic acid with less degradation of the cellulose than with peroxymonosulfuric acid. This was explained on the basis of the electrophilic and nucleophilic properties of these acids that improved the delignification of eucalyptus kraft pulp. The effluents generated in these steps involving the peracids had greater color, chemical oxygen demand (COD), and total phenols correlating with the amount of lignin removed and the analyses of bioassays did not show acute toxicity from effluents coming from a peroxymonosulfuric acid step. The delignification with peracids may possibly reduce the use of chlorine dioxide in a sequence involving bleaching with elemental free chlorine (ECF), in this way reducing the concentration of organic chlorides (AOX) in the bleaching effluent

Efectos de una zona urbana sobre la comunidad de macroinvertebrados bentónicos de un ecosistema fluvial del sur de Chile

Un cuerpo de agua dulce saludable puede proveer de numerosos beneficios a la sociedad, aunque actualmente la degradación de este tipo de ecosistemas se ha visto incrementada por el establecimiento de centros urbanos en sus riberas. En este estudio analizamos el efecto espacial de estas zonas sobre la calidad del agua, utilizando la comunidad de macroinvertebrados bentónicos como bioindicadores de contaminación fluvial en el canal Gibbs de la comuna de Temuco (38° 46' S 72° 38' W). Los muestreos fueron realizados en la época de primavera en seis sitios. El macrozoobentos estuvo compuesto por un total de 15 taxones, correspondientes a organismos tolerantes a condiciones de anoxia y a altas concentraciones de materia orgánica, tales como anfípodos (RyaleIla), dípteros (Quironomidae) y oligoquetos (Oligochaeta). Hubo una marcada diferencia en la composición y abundancia de taxones entre las zonas pre-urbana, urbana y post-urbana (ANOS1M R Global = 0.882; P = 0.001), tendencia que también fue registrada por los parámetros fisicoquímicos (ANOS1M R Global = 0.498; p = 0.001), de los cuales el pH, sólidos suspendidos totales y oxígeno disuelto son los que mejor explicaron los patrones observados en el macrozoobentos. Los resultados obtenidos con el índice biótico de familias (ChIBF) fueron similares a los registrados en las partes bajas de las cuencas del Sur de Chile y la comunidad de invertebrados demostró ser sensible a perturbaciones de origen antrópico.A healthy body of freshwater can provide numerous benefits to the society, although currentIy, the degradation of such ecosys­tems has been increased due to the establishment of urban areas along its riverbanks. In this study we analyzed the spatial effect of these zones on the water quality, using the benthonic macroinvertebrate communities as bioindicators of fluvial con­tamination in the Gibbs channel ofthe Temuco commune (38°46'S n038'W). The samplings were performed in spring, in six sites. The macrozoobentos was composed by a total of 15 taxa, corresponding to organisms tolerant to anoxic conditions and high concentrations of organic matter, such as amphipods (Hyalella), dipterans (Quironomidae), and oligochaetes (Oligochae­ta). There was a marked difference in the composition and abundance of taxa between the pre-urban, urban, and post-urban areas (ANOSIM Global R = 0.882,p = 0.001) tendency that was also recorded by the physicochemical parameters (ANOS 1M Global R = 0.498, p = 0.001), of which pR, total suspended solids, and dissolved oxygen are those that best explained the patterns observed in the macrozoobentos. The results obtained with the biotic family index (ChIBF) were similar to those registered in the lower parts of the basins of southern Chile and the invertebrate community was shown to be sensitive to anthropogenic disturbances