Francisco D. Fernández Martín

Use of liming in the remediation of soils polluted by sulphide oxidation: A leaching-column study

Pure CaCO(3) in ascending quantities was added to a soil to study the effect of liming after contamination by an acidic solution from the oxidation of pyrite tailings. The samples were placed in percolation columns, and soils and leachates were monitored. In the soil samples, the mineralogy, pH, CaCO(3), iron, and total content in Cu, Zn, As, Cd, and Pb were determined. The presence of CaCO(3) in the soils considerably limited their acidification, favouring the precipitation of Cu, Zn, and Cd, and promoting precipitation of iron and SO(4)(2-) ions in the form of iron hydroxysulphates and gypsum. The iron hydroxysulphates tended to retain the less mobile elements (As, and Pb) near the top of the soil. The more mobile elements (Zn, Cd and Cu) precipitated in deeper layers, directly related mainly to the CaCO(3) added and to pH. The CaCO(3) clearly did not reduce Zn and Cd toxicity effectively enough, given that the concentrations of both elements were above the toxic level in all leachates. The amounts of liming needs to be properly controlled, as excessively high pH limits As fixing, at the same time as the effectiveness of CaCO(3) is limited by coating precipitation, reducing its capacity to react with the acidic solution.

Ambient trace element background concentrations in soils and their use in risk assessment.

The definition of ambient background concentrations (ABCs) is used in this study to assess the potential environmental risk of trace elements in soils and parent materials from Granada, Spain. Two different layers of soil (0-20 and 20-40 cm) and parent material samples were collected at 93 sites. From cumulative frequency distribution curves, ABCs for As, Co, Cu, Cr, Ni, Pb and Zn were estimated at 3.5-20, 7-23, 13-25.6, 29-66, 7-20, 15-36, and 5.5-76 mg kg(-1), respectively. Tukey box-plots were used to discriminate different concentration classes and identify potentially contaminated sites. Weakly-weathered soils (Entisols) over carbonate materials showed the lowest background contents, the most developed soils (Alfisols) over metamorphic rocks the highest ones. Outliers were mainly found near a former iron mine where arsenic concentrations were by far exceeding the corresponding regional ABC. These soils were however, not toxic to Escherichia coli and Vibrio fischeri. The prediction of site-specific ABCs together with bioavailability and toxicity assessment is a valuable tool for giving further insight into the risk of trace elements in soils.

Remediation measures and displacement of pollutants in soils affected by the spill of a pyrite mine.

The soils affected by the spill of a pyrite mine were analysed in 100 sampling points at three depths (0-10, 10-30, and 30-50 cm) in 1998 (after the tailings were removed), 1999 (after the cleaning of the highly contaminated areas), and 2004 (after the tilling of the upper 20-25 cm). The comparative study reveals that the removal of the tailings left a heterogeneous distribution pattern of the contaminants, with highly polluted spots alternating with less contaminated areas. The cleanup did not substantially lower the concentration in the highly polluted soils, and the spread of the pollutants increased the concentration in As and Pb in the uppermost 10 cm of 60% of the soils, while the Zn and Cd concentrations increased in only 30% of the soils. Given the high concentration of pollutants in the topsoil (especially As), the tilling of the upper 20-25 cm, despite reducing the average concentration of pollutants in the uppermost 10 cm, did not substantially lower the percentage of soils that exceeded the concentration of 40 mg As kg(-1) dry soil and almost doubled the percentage of soils that surpassed this concentration between 10 and 30 cm. Meanwhile, the displacement of Zn and Cd within the soil supported the reduction in the percentage of soils that in the upper 10 cm exceeded the reference concentrations of these elements (900 mg Zn kg(-1) dry soil and 2 mg Cd kg(-1) dry soil), and the percentage of soils exceeding these concentrations between 10 and 50 cm in depth did not increase. Six years after the spill and at the end of all remediation measures, the intervention levels defined by the Environmental Agency of the Regional Government of Andalusia for natural parks were exceeded in the uppermost 10 cm in 35% of the soils.

Trace element concentrations and background values in the arid soils of Hormozgan Province of southern Iran

Trace element concentrations in soils of arid regions of southern Iran are described to assess the concentration ranges of selected elements in a variety of soils and rocks, and to evaluate the potential bioavailability of trace elements in relation to soil properties. The study area was classified into three sub-regions consisting of (1) shale, gypsum, and limestone (western part), (2) igneous rocks and limestone (northern part), and (3) sandstone and limestone (eastern and northeastern part). The gained background values of trace elements were used for evaluating the quality and degree of contamination with native and also with anthropogenic elements of studied soils. Some soil samples indicated a significant enrichment for Pb and Ni, with an enrichment factor (EF) of around 6.0. Soils have only been cultivated for few years compared to hundreds and thousands of years for many agricultural soils; therefore, there has been less crop removal. Furthermore, soils are not highly weathered because they are in an arid climate with low precipitation, which results in a slow rate of weathering. However, slight elemental differences between soil horizons indicated that most soils are poorly developed and also represented the similarity of trace element contents between soils and parent materials.

Arsenic Behaviour in Polluted Soils After Remediation Activities

Arsenic (As) in soil is a serious environmental problem due to its potential high toxicity. Under field conditions As can accumulate in contaminated soils because it is only partially removed by leaching, methylation, and erosion or because it is only slightly taken up and accumulated by plants. Chemically, As exists as organic and inorganic species. It has two main oxidation states (+III and +V), depending on the type and amounts of sorbents, pH, redox potential (Eh), and microbial activity (Yong & Mulligan, 2004). Inorganic compounds are the most frequent in soil due to their water solubility. The most thermodynamically stable species within the pH range 4.0-8.0 include H3AsO3 of AsIII, and HAsO42and H2AsO4of Asv (Smith et al., 1998). Asv species predominate in soil solutions under moderate reducing conditions, but AsIII forms are more abundant when the redox potential is below 500 mV, according to Masscheleyn et al. (1991). These authors also indicate that a rise in pH, or a fall in Asv to AsIII, boost the concentration of As in the solution, while its solubility under moderately reducing conditions is controlled by the dissolution of iron hydroxides (Marin et al. 1993). On the other hand, it is well known that the As concentration in a soil solution is governed by the physical and chemical properties of the soil, which influence adsorption-desorption processes. Arsenic has a high affinity for oxidic surfaces, and the reactivity of the oxides varies considerably with the pH, the charge density, and the composition of the soil solution. The soil texture and the nature of the mineral constituents also affect adsorption processes (Hiltbold, 1974). Pierce and Moore (1980) demonstrated the specificity of the surface of iron hydroxides and the influence of pH in As adsorption. In soils, As has low mobility and under reducing conditions the concentration of dissolved As in soil solution declines. The availability of this element in soils can increase under acidic conditions (mainly pH below 5), due to the greater solubility of the iron and aluminium compounds, which augment As toxicity (O’Neill, 1995). In general, the mobility of this element is directly related to the total amount of As and inversely to time as well as to the iron and aluminium content; also, under oxidation conditions, its bioavailability is strongly limited (Kabata-Pendias & Pendias, 2001).

Diseño de escalas de actitudes para la formación docente en tecnologías

En este articulo se presenta una escala elaborada con el fin de conocer las actitudes sobre la formacion y perfeccionamiento en las nuevas tecnologias de la informacion (NTIC) de los profesionales de la educacion ya que muchos no han desarrollado aun una actitud favorable hacia ellas. Esta puede ser una de las razones por las que no las utilicen en el aula, lo que conlleva una falta de aprovechamiento de los beneficios que pueden aportar tanto a su trabajo como al aprendizaje de sus alumnos. Para ello, despues se teoriza sobre las actitudes y la formacion y perfeccionamiento en NTIC, finalizando con la construccion de una Escala Likert.

Efectos de un programa de Aprendizaje-Servicio en el alumnado universitario

espanolIntroduccion. La baja productividad de la Educacion Superior requiere urgentemente respuestas institucionales dirigidas a la mejora calidad de la ensenanza universitaria, que contribuyan al desarrollo entre el alumnado de competencias clave para el aprendizaje permanente. En este sentido, el proposito de esta investigacion fue explorar los efectos de un programa de intervencion, basado en las metodologias aprendizaje-servicio y mentoria entre iguales, dirigido a mejorar las competencias sociales y de aprender a aprender del alumnado universitario. Metodo. La muestra estuvo compuesta por 78 alumnos/as universitarios/as de 5 titulaciones relacionadas con la profesion docente de la Universidad de Huelva (Espana). El diseno metodologico adoptado fue un diseno cuasi-experimental pretest-postest, empleando pruebas estandarizadas para evaluar las variables dependientes. La intervencion consistio en 481 sesiones de mentoria, 423 individuales y 58 grupales, entre el alumnado universitario participante, en calidad de mentores, previamente entrenados en 3 sesiones de formacion, y alumnado de educacion obligatoria. Estas sesiones se extendieron a lo largo del segundo y tercer trimestre del curso escolar 2013/2014 en tiempo extraescolar, con una frecuencia de una sesion de mentoria semanal entre cada pareja de mentores y su correspondiente alumno/a, con una duracion de 90 minutos. Resultados. Los resultados obtenidos arrojan diferencias estadisticamente significativas, a favor de la fase postest en habilidades sociales y de las estrategias de aprendizaje y motivacion de los participantes. Discusion y conclusion. Estos resultados coinciden con las evidencias empiricas que la literatura especializada arroja cuando se emplean las metodologias de aprendizaje-servicio y mentoria entre iguales como base de un programa de intervencion EnglishIntroduction. The low productivity that prevailing in recent years in Higher Education requires urgently institutional responses aimed to improving quality of university education contributing to the development among students of key competences for lifelong learning. In this sense, the aim of this research was to explore the effects of an intervention program, based on service-learning and peer mentoring methodologies, to enhance social skills and the learn to learn skill of university students. Method. The sample was composed of 78 university students of 5 degrees related to the teaching profession of the University of Huelva (Spain). The methodological design adopted was quasi-experimental pretest-posttest, using standardized tests to evaluate the dependent variables. The intervention consisted of 481 mentoring sessions, 423 individual and 58 in group, among the university students, as mentors, previously trained in 3 sessions of training, and students in Compulsory Education. These sessions spread throughout the second and third quarters of the school year 2013/2014 during out of school time, a weekly mentoring session among the couple of mentors with their mentee lasted for 90 minutes each. Results. The results show statistically significant differences in favour of the posttest phase in social skills and strategies for learning and motivation of the participants. Discussion and Conclusion. These results agree largely whit the empirical evidences from specialized literature show when service-learning and peer mentoring methodology are used as the basis for an intervention program.

Adquisición de estereotipos sexuales a través de los medios de comunicación

Resumen es: Es necesario establecer una educacion especifica, desde la escuela y en colaboracion con la familia, sobre la masiva informacion que se trasmite en los ...