Application of Sustainable Remediation Techniques for Heavy Metal Reduction in Polluted Rivers in Mining Zones: Study Area Ponce Enriquez

Mining activity in Ecuador is primarily artisanal and small-scale. Rivers near the mining county of Camilo Ponce Enriquez have been severely affected by this type of mining. A field study was conducted encompassing 29 sites on the rivers Siete, Fermin, and Pagua during sampling campaigns that took place in both dry (December) and wet seasons (February). Physiochemical parameters and heavy metal concentrations were measured to enable environmental characterization of the rivers. Results revealed that most of the sampled sites had bad water quality and exceeded the environmental limits of heavy metal concentrations set by the Ecuadorian government. A parallel pilot investigation was performed for reducing the heavy metal concentrations in water ecosystems polluted by mining activities using bioremediation techniques. The bioremediation technique applied in the study used bacteria from a wastewater digestor and sugarcane bagasse as a carbon source to support the bacterial community. Sulfide was measured to monitor bacterial activity in experimental bioreactors containing local acid mine drainage (AMD). The results obtained were encouraging, as a significant decrease in heavy metal concentration was observed to nearly the level of Ecuadorian environmental regulations for Al, Cd, Cu, Fe, Pb, and Zn concentrations in freshwater in a set of bioreactors. Keywords: acid drainage, artisanal mining, bioremediation, heavy metals, pollution. Resumen La actividad minera en el Ecuador es principalmente artesanal y de pequeña escala. Los ríos cercanos al área minera de Camilo Ponce Enríquez se han visto severamente afectados por este tipo de minería. Se realizó un estudio de campo en 29 sitios sobre los ríos Siete, Fermín y Pagua durante campañas de muestreo que se realizaron tanto en la época seca (diciembre) como en época húmeda (febrero). Se midieron parámetros fisicoquímicos y concentraciones de metales pesados para permitir la caracterización ambiental de los ríos. Los resultados revelaron que la mayoría de los sitios muestreados tienen agua de mala calidad y excedieron los límites ambientales de concentración de metales pesados establecidos por el gobierno ecuatoriano. También se realizó una investigación piloto paralela destinada a reducir las concentraciones de metales pesados en ecosistemas acuáticos contaminados por actividades mineras utilizando técnicas de biorremediación. La técnica de biorremediación aplicada en el estudio utilizó bacterias de un digestor de aguas residuales y bagazo de caña de azúcar como fuente de carbono para apoyar a la comunidad bacteriana. Se midió el sulfuro para controlar la actividad bacteriana en biorreactores experimentales que contenían drenaje ácido minero (AMD) local. Los resultados obtenidos son alentadores ya que en un conjunto de biorreactores se observó una disminución significativa de las concentraciones de algunos metales pesados alcanzando casi en su mayoría el nivel permisible según las regulaciones ambientales ecuatorianas para las concentraciones de Al, Cd, Cu, Fe, Pb y Zn en agua dulce. Palabras Clave: drenajes ácidos, minería artesanal, biorremediación, metales pesados, contaminación

Dynamic scaling approach to study time series fluctuations

We propose a new approach for properly analyzing stochastic time series by mapping the dynamics of time series fluctuations onto a suitable nonequilibrium surface-growth problem. In this framework, the fluctuation sampling time interval plays the role of time variable, whereas the physical time is treated as the analog of spatial variable. In this way we found that the fluctuations of many real-world time series satisfy the analog of the Family-Viscek dynamic scaling ansatz. This finding permits to use the powerful tools of kinetic roughening theory to classify, model, and forecast the fluctuations of real-world time series.Comment: 25 pages, 7 figures, 1 tabl

[Reliability of Commercial Tests for Hepatitis C Virus].

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Flame burning speeds and combustion characteristics of undiluted and nitrogen-diluted hydrogen-nitrous oxide mixtures

In the present study, some explosive properties of undiluted and nitrogen-diluted H_2–N_2O mixtures were characterized. Laminar burning speeds and the explosion-induced pressure rises were determined experimentally for a range of mixture equivalence ratios (ϕ=0.15−1.0), dilutions (0-55%N_2) and initial pressures (20-80kPa). The measured burning speeds were used to validate laminar burning speed computations using a detailed chemical kinetic mechanism. The computations were then used to estimate burning speeds at high initial pressure and low dilution conditions that could not be measured experimentally. The results demonstrate that hydrogen–nitrous oxide mixtures exhibit laminar burning speeds as large as 350 cm/s and pressure rise coefficients (K_g) as large as 35 MPa m/s. Also, flames in lean mixtures are shown to be highly unstable which can lead to flame acceleration and possible deflagration-to-detonation transition

Structural Modeling of Straw Bale Loadbearing Wall

In Ecuador, there are qualitative and quantitative housing deficits that must be covered with materials that produce seismic-resistant, energy-efficient buildings that do not require a large amount of energy to be produced. Several studies indicate that the answer lies in straw bale structures. However, for these to be considered by designers, aids are needed to facilitate their structural modeling in specialized computer programs. Through literature reviews, the present research proposes a model that adapts the specific structural considerations of straw bale buildings to the tools available in a design program. Keywords: structure, bales, straw, model, program, design. Resumen En el Ecuador existe un déficit cualitativo y cuantitativo de viviendas que debe ser cubierto con materiales que produzcan edificaciones sismo resistentes, energéticamente eficientes y a la vez que no requieran gran cantidad de energía para ser producidos. Varios estudios señalan que la respuesta está en las estructuras elaboradas con fardos de paja. Sin embargo, para que éstas sean consideradas por los diseñadores son necesarias ayudas para facilitar su modelamiento estructural en programas informáticos especializados. La presente investigación, a través de revisiones bibliográficas, propone un modelo que adapta las consideraciones estructurales específicas de las construcciones con fardos de paja a las herramientas disponibles en un programa de diseño. Palabras Clave: estructura, fardos, paja, modelo, programa, diseñ

Experimental investigation of spark ignition energy in kerosene, hexane, and hydrogen

Quantifying the risk of accidental ignition of flammable mixtures is extremely important in industry and aviation safety. The concept of a minimum ignition energy (MIE), obtained using a capacitive spark discharge ignition source, has traditionally formed the basis for determining the hazard posed by fuels. While extensive tabulations of historical MIE data exist, there has been little work done on ignition of realistic industrial and aviation fuels, such as gasoline or kerosene. In the current work, spark ignition tests are performed in a gaseous kerosene–air mixture with a liquid fuel temperature of 60°C and a fixed spark gap of 3.3 mm. The required ignition energy was examined, and a range of spark energies over which there is a probability of ignition is identified and compared with previous test results in Jet A (aviation kerosene). The kerosene results are also compared with ignition test results obtained in previous work for traditional hydrogen-based surrogate mixtures used in safety testing as well as two hexane–air mixtures. Additionally, the statistical nature of spark ignition is discussed