Bioavailability and extraction of heavy metals from contaminated soil by Atriplex halimus

Pot experiments were performed to evaluate the phytoremediation capacity of plants of Atriplex halimus grown in contaminated mine soils and to investigate the effects of organic amendments on the metal bioavailability and uptake of these metals by plants. Soil samples collected from abandoned mine sites north of Madrid (Spain) were mixed with 0, 30 and 60 Mg ha?1 of two organic amendments, with different pH and nutrients content: pine-bark compost and horse- and sheep-manure compost. The increasing soil organic matter content and pH by the application of manure amendment reduced metal bioavailability in soil stabilising them. The proportion of Cu in the most bioavailable fractions (sum of the water-soluble, exchangeable, acid-soluble and Fe?Mn oxides fractions) decreased with the addition of 60 Mg ha?1 of manure from 62% to 52% in one of the soils studied and from 50% to 30% in the other. This amendment also reduced Zn proportion in water-soluble and exchangeable fractions from 17% to 13% in one of the soils. Manure decreased metal concentrations in shoots of A. halimus, from 97 to 35 mg kg?1 of Cu, from 211 to 98 mg kg?1 of Zn and from 1.4 to 0.6 mg kg?1 of Cd. In these treatments there was a higher plant growth due to the lower metal toxicity and the improvement of nutrients content in soil. This higher growth resulted in a higher total metal accumulation in plant biomass and therefore in a greater amount of metals removed from soil, so manure could be useful for phytoextraction purposes. This amendment increased metal accumulation in shoots from 37 to 138 mg pot?1 of Cu, from 299 to 445 mg pot?1 of Zn and from 1.8 to 3.7 mg pot?1 of Cd. Pine bark amendment did not significantly alter metal availability and its uptake by plants. Plants of A. halimus managed to reduce total Zn concentration in one of the soils from 146 to 130 mg kg?1, but its phytoextraction capacity was insufficient to remediate contaminated soils in the short-to-medium term. However, A. halimus could be, in combination with manure amendment, appropriate for the phytostabilization of metals in mine soils.

Initializing the DSSAT-Century model: inverse calibration of carbon pools from apparent soil N mineralization

The CENTURY soil organic matter model was adapted for the DSSAT (Decision Support System for Agrotechnology Transfer), modular format in order to better simulate the dynamics of soil organic nutrient processes (Gijsman et al., 2002). The CENTURY model divides the soil organic carbon (SOC) into three hypothetical pools: microbial or active material (SOC1), intermediate (SOC2) and the largely inert and stable material (SOC3) (Jones et al., 2003). At the beginning of the simulation, CENTURY model needs a value of SOC3 per soil layer which can be estimated by the model (based on soil texture and management history) or given as an input. Then, the model assigns about 5% and 95% of the remaining SOC to SOC1 and SOC2, respectively. The model performance when simulating SOC and nitrogen (N) dynamics strongly depends on the initialization process. The common methods (e.g. Basso et al., 2011) to initialize SOC pools deal mostly with carbon (C) mineralization processes and less with N. Dynamics of SOM, SOC, and soil organic N are linked in the CENTURY-DSSAT model through the C/N ratio of decomposing material that determines either mineralization or immobilization of N (Gijsman et al., 2002). The aim of this study was to evaluate an alternative method to initialize the SOC pools in the DSSAT-CENTURY model from apparent soil N mineralization (Napmin) field measurements by using automatic inverse calibration (simulated annealing). The results were compared with the ones obtained by the iterative initialization procedure developed by Basso et al., 2011.

Amelioration of a degraded acid soil from SW Spain by no-tillage and Ca-amendment

En los suelos, el exceso de acidez lleva asociado deficiencias en ciertos nutrientes y una alta disponibilidad de aluminio, t��xico para los cultivos propios del ambiente mediterr��neo. Su laboreo, provoca la p��rdida de materia org��nica (MO), deteriora su estructura y reduce la actividad biol��gica, provocando en ��ltima instancia una menor calidad del suelo. Es de esperar pues que cuando se labran suelos ��cidos, sus problem��ticas particulares tiendan a agravarse. En nuestra zona de estudio, la ���ra��a��� de Ca��amero (Extremadura, Espa��a), predominan los suelos muy ��cidos y degradados por un laboreo inadecuado. Las ra��as constituyen amplias plataformas casi horizontales, con unos suelos muy viejos (Palexerults), que se caracterizan por tener el complejo de cambio dominado por el aluminio, y un pH ��cido que decrece en profundidad. Poseen un potente horizonte Bt rico en arcillas caolin��ticas, que propicia que en periodos con exceso de lluvia, se generen capas colgadas de agua cercanas a la superficie. En torno a los a��os 1940���s estos suelos, que previamente sosten��an un alcornocal, o su matorral de sustituci��n, se pusieron en cultivo. El laboreo aceler�� la mineralizaci��n de la materia org��nica, agrav�� los problemas derivados del exceso de acidez y condujo al abandono de los campos cultivados por falta de productividad. Para recuperar la calidad de estos suelos degradados y obtener unos rendimientos compatibles con su uso agr��cola es necesario, por un lado, aplicar enmiendas que eleven el pH y reduzcan la toxicidad del aluminio y, por otro, favorecer el incremento en el contenido en MO. En 2005 se implant�� en esta ra��a un ensayo de campo para estudiar la influencia del no laboreo y de la utilizaci��n de una enmienda c��lcica en par��metros relacionados con la calidad del suelo en un cultivo forrajero. El dise��o experimental fue en parcelas divididas con cuatro repeticiones donde el factor principal fue el tipo de laboreo, no laboreo (NL) frente a laboreo convencional (LC), y el factor secundario el uso o no de una enmienda c��lcica. La enmienda consisti�� b��sicamente en una mezcla de espuma de azucarer��a y yeso rojo y se incorpor�� al comienzo del ensayo hasta los 7 cm de profundidad. Desde el comienzo del ensayo el NL influy�� positivamente en el contenido de carbono org��nico total (COT) y particulado (COP), mientras que la enmienda tuvo una ligera influencia al principio del ensayo en ambos pero su efecto positivo se desvaneci�� con el paso del tiempo. Los mayores contenidos en COT y POC se observaron cuando se combin�� el NL con la enmienda. La enmienda increment�� con rapidez el pH, y el Ca, y disminuy�� el contenido en aluminio hasta una profundidad de 50 cm, incluso en NL, y mejor�� ligeramente la agregaci��n del suelo. El NL por s�� solo, gracias al aumento en POC, TOC y las prote��nas del suelo relacionadas con la glomalina (PSRG), que son capaces de formar compuestos estables no t��xicos con el aluminio, tambi��n contribuy�� a la reducci��n de la toxicidad de aluminio en la capa m��s superficial. Cuando en las campa��as con exceso de precipitaciones se generaron capas colgadas de agua pr��ximas a la superficie, el NL gener�� unas condiciones m��s favorables para la germinaci��n y desarrollo del cultivo, resultando en una producci��n m��s alta que el LC. A ello contribuy�� la mayor capacidad de almacenamiento de agua y la mayor transmisividad de esta hacia abajo, en la capa m��s superficial (0-5 cm) que propici�� una menor saturaci��n por agua que el LC. Respecto a los par��metros relacionados con la agregaci��n, el NL aument�� los macroagregados hasta los 10 cm de profundidad y favoreci�� la acumulaci��n de CO y N en todas las fracciones de tama��o de agregados. Sin embargo, la recuperaci��n del grado de macroagregaci��n tras el cese del laboreo resulta lenta en comparaci��n con otros suelos, posiblemente debido al bajo contenido en arcilla en el horizonte Ap. En comparaci��n con el NL, la enmienda mostr�� tambi��n un efecto positivo, aunque muy ligero, en la agregaci��n del suelo. En contradicci��n con otros estudios en suelos ��cidos, nuestros resultados indican la existencia de una jerarqu��a de agregados, y destacan el papel importante de la MO en la mejora de la agregaci��n. Tanto el NL como la enmienda favorecieron por separado varias propiedades qu��micas, f��sicas y biol��gicas del suelo, pero, en general, encontramos los mayores beneficios con su uso combinado. Adem��s, a largo plazo el efecto positivo de NL en las propiedades del suelo fue en aumento, mientras que el efecto beneficioso de la enmienda se limit�� b��sicamente a las propiedades qu��micas y se desvaneci�� en pocos a��os. Destacamos que las condiciones meteorol��gicas a lo largo del ensayo beneficiaron la producci��n de biomasa en NL, y en consecuencia las propiedades relacionadas con la materia org��nica, por lo que son un factor a tener en cuenta a la hora de evaluar los efectos de la enmienda y el laboreo sobre las propiedades del suelo, especialmente en zonas donde esas condiciones son muy variables entre una campa��a y otra. Los resultados de este estudio han puesto de manifiesto que el NL no ha mermado la eficacia de la enmienda caliza, posiblemente gracias a la alta solubilidad de la enmienda aplicada, es m��s, el manejo con NL y enmienda es el que ha favorecido en mayor medida ciertos par��metros de calidad del suelo. Por el contrario el LC s�� parece anular los beneficios de la enmienda en relaci��n con las propiedades relacionadas con la MO. Por tanto, cabe concluir que la combinaci��n de NL y la enmienda es una pr��ctica adecuada para mejorar las propiedades qu��micas y f��sicas de suelos ��cidos degradados por el laboreo. ABSTRACT Excessive acidity in soils is associated with deficiencies in certain nutrients and high concentrations of available aluminum, which is toxic for most Mediterranean crops. Tilling these soils results in the loss of soil organic matter (SOM), damages soil structure and reduces biological activity, ultimately degrading soil quality. It is expected, therefore, that when acid soils are tilled, their particular problems will tend to get worse. In our study area, the "Ca��amero���s Ra��a��� (Extremadura, Spain), acid soils degraded by an inappropriate tillage prevail. Ra��as are large and flat platforms with very old soils (Palexerults), which are characterized by an exchange complex dominated by aluminum and an acid pH which decreases with depth. These soils have a strong Bt horizon rich in kaolinite clays, which encourages the formation of perched water-tables near the soil surface during periods of excessive rain. During the first third of the 20th century, these soils, that previously supported cork oak or its scrub replacement, were cultivated. Tillage accelerated the mineralization of the SOM, aggravating the problems of excessive acidity, which finally led to the abandonment of the land due to low productivity. To recover the quality of these degraded soils and to obtain consistent yields it is necessary, first, to apply amendments to raise the pH and reduce aluminum toxicity, and second to encourage the accumulation of SOM. In 2005 a field trial was established in the Ra��a to study the influence of no-tillage and the use of a Ca-amendment on soil quality related parameters in a forage crop agrosystem. The experimental design was a split-plot with four replicates where the main factor was tillage type, no-tillage (NT) versus traditional tillage (TT) and the secondary factor was the use or not of a Ca-amendment. The Ca-amendment was a mixture of sugar foam and red gypsum that was incorporated into the top 7 cm of the soil. Since the beginning of the experiment, NT had a positive influence on total and particulate organic carbon (TOC and POC, respectively), while the Ca-amendment had a small positive influence at the beginning of the study but its effect diminished with time. The highest TOC and POC contents were observed when NT and the Ca-amendment were combined. The Ca-amendment, even under NT, rapidly increased pH and Ca, and decreased the aluminum content to a depth of 50 cm, as well as improving soil aggregation slightly. NT, due to the increased POC, TOC and Glomalin-related soil proteins (GRSP), which can form stable non-toxic compounds with aluminum, also contributed to the reduction of aluminum toxicity in the upper layer. When perched water-tables near the soil surface were formed in campaigns with excessive rainfall, NT provided more favorable conditions for germination and crop development, resulting in higher yields compared with TT. This was directly related to the higher water storage capacity and the greater transmissivity of the water downwards from the upper layers, which led to lower water saturation under NT compared with TT. With regards to the aggregation-related parameters, NT increased macroaggregation to a depth of 10 cm and favored the accumulation of OC and N in all aggregate size fractions. However, the degree of recovery of macroaggregation after tillage ceased was slow compared with other soils, possibly due to the low clay content in the Ap horizon. Compared with NT, the Ca-amendment had a slight positive effect on soil aggregation. In contrast to other studies in acid soils, our results indicate the existence of an aggregate hierarchy, and highlight the important role of SOM in improving aggregation. Both NT and the Ca-amendment separately favored various chemical, physical and biological soil properties, but in general we found the greatest benefits when the two treatments were combined. In addition, the positive effect of NT on soil properties increased with time, while the beneficial effect of the Ca-amendment, which was limited to the chemical properties, vanished after a few years. It is important to note that the meteorological conditions throughout the experiment benefited biomass production under NT and, as a consequence, organic matter related properties. This suggests that meteorological conditions are a factor to consider when evaluating the effects of Ca-amendments and tillage on soil properties, especially in areas where such conditions vary significantly from one campaign to another. The results of this study show that NT did not diminish the effectiveness of the Ca-amendment, possibly due to the high solubility of the selected amendment. Moreover, the combination of NT and the Ca-amendment was actually the management that favored certain soil quality parameters the most. By contrast, TT seemed to nullify the benefits of the Ca-amendment with regards to the OM related properties. In conclusion, the combination of NT and the application of a Ca-amendment is an advisable practice for improving the chemical and physical properties of acid soils degraded by tillage.

Estudio del empleo de cubiertas vegetales temporales para la regulaci��n del r��gimen h��drico, crecimiento y manejo sostenible del vi��edo

RESUMEN El ensayo se llevo a acabo en un vi��edo de Syrah durante 8 a��os y en un vi��edo de Merlot durante 3 a��os. Ambos vi��edos regados y situados en Colmenar de Oreja (Madrid) (40�� 8���N, 3�� 23���W) con clima t��picamente Mediterr��neo. Siete tratamientos con cubiertas vegetales se han comparado con dos tratamientos con suelo desnudo usados como control. Las cubiertas vegetales fueron seis tratamientos de cereales (Centeno) y un tratamiento de enyerbado autosembrado (Bromus spp) y los tratamientos de suelo desnudo fueron uno manejado con laboreo y otro manejado con herbicida. Los seis tratamientos de centeno se han manejado de seis formas distintas. La primera sembrada todos los a��os y eliminada en brotaci��n mediante herbicida de post-emergencia. La segunda sembrada todos los a��os y eliminada un mes despu��s de la brotaci��n mediante siega. La tercera sembrada todos los a��os y eliminada en floraci��n mediante siega. La cuarta sembrada todos los a��os y eliminada en brotaci��n mediante herbicida de post-emergencia. La quinta sembrada todos los a��os y eliminada un mes despu��s de la brotaci��n mediante siega. La sexta sembrada todos los a��os y eliminada en floraci��n mediante siega. La utilizaci��n de cubiertas vegetales ha tenido efectos beneficiosos sobre el contenido en materia org��nica, la compactaci��n y la infiltraci��n del suelo, mejorando las condiciones para el desarrollo de las ra��ces. Estas mejoras y la escasa competencia de la competencia durante el crecimiento del sistema radical de la vid han producido un incremento del sistema radical en las plantas mantenidos con cubierta vegetal. La competencia de las cubiertas vegetales ha reducido la disponibilidad h��drica de la vid, increment��ndose la absorci��n en zonas con mayor disponibilidad h��drica (como la l��nea) antes de floraci��n. El mayor desarrollo radical de las vides con cubierta autosembrada ha permitido agotar m��s intensamente las reservas de agua en el suelo. La competencia de las cubiertas ha reducido en mayor medida el desarrollo vegetativo que el productivo. Lo que ha disminuido, en algunas cubiertas vegetales, el consumo h��drico de la vid, aumentando el potencial h��drico foliar y la fotos��ntesis durante la maduraci��n. Sin embargo, el incremento en la fotos��ntesis no ha compensado el mayor desarrollo foliar de los tratamientos con suelo desnudo, lo que ha provocado que estos tratamientos presenten la producci��n de materia seca m��s elevada. El empleo de cubiertas vegetales ha reducido la producci��n principalmente limitando el n��mero de bayas por racimo, ya que el aporte de riego ha minimizado los efectos del manejo del suelo sobre el tama��o de baya. La utilizaci��n de cubiertas vegetales temporales ha mejorado la iluminaci��n de los racimos, lo que ha producido un aumento de la s��ntesis de antocianos durante las primeras fases de la maduraci��n, pero un incremento de la degradaci��n de los mismos al final de la maduraci��n. Esto ha provocado que durante la vendimia los tratamientos de suelo desnudo presenten un mayor contenido de antocianos por baya que los tratamientos mantenidos con cubierta temporal. Estos resultados muestran que el efecto del manejo del suelo depende en gran medida de las condiciones del medio, y que sus efectos en climas calidos y secos son muy distintos a los observados en climas frescos y h��medos. ABSTRACT The trial was conducted over a period of 8 years in a Syrah vineyard and over a period of 3 years in a Merlot vineyard. Both vineyards were irrigated and situated near Colmenar de Oreja (Madrid) (40�� 8���N, 3�� 23���W) a typical Mediterranean climate. Seven Annual cover crops treatments were compared to two bare soil treatments, used as control. Cover crops were six cereals treatments (Rye) and one auto-sowing treatment (Bromus spp) and the treatments of bare soil were one tilled management treatment and another with herbicide treatment. The six Cereal treatments were managed in different manners. First sowing every year and were eliminated in bud breaking with post-emergency herbicide. The second sowing annually and were eliminated one month after bud breaking through harvesting. The third sowing annually and were eliminated in flowering by mowing. The fourth sowing annually and were eliminated with post-emergency herbicide in bud breaking. The fifth sowing annually and were eliminated by mowing one month after bud breaking. . The third sowing annually was eliminated by mowing in flowering. The use of annual cover crop have improved soil organic matter, soil infiltration rate and soil solidity, resulting in a more favourable environment for roots growth. These improvements and low competitive ability during root growing have increases grapevine root density in plant management with cover crop. The Cover crop ability reduced plant available water, increasing root water uptake in the soil with more available water (such us line) before flowering. More growth of grapevine root density with auto-sowed cover crops has allowed using the water under soil more rapidly. The cover crop ability has reduced vegetative growth more than yield. What has been reduced in some vegetative cover crop has been the consumption of water, and increasing the leaf water potential and foliar and photosynthesis during growth activity. Moreover, the increased in photosynthesis activity could not ���Compensate��� higher leaf growth of treatment of bare soil, where these treatments had resulted in the greatest amount of dry material. The use of cover crops has reduced the crop mainly reducing the fruit set, because the irrigation had reduced the cover crop effect in the berry growth. The use of temporary cover crop increased berry sunlight exposure and skin anthocyanin synthesis during early rippenig, but excessively high temperature increased anthocyanin degradation during last part of ripenning. So, at the vineyard harvest period the treatments with bare soil plant had a more anthocyanin content per grape than the temporary cover crop plant treatments. These results suggest that the effects of soil handling mainly depends on the environmental condition, and their effects in hot and dry climate are so different from the effects in cold and moist climates.

Indicators of sustainability of agriculture and livestock in Spain - Indicadores de sostenibilidad de la agricultura y ganader��a espa��ola

Sustainability is an adjective used to characterize agriculture according to the degree of fulfillment of goals. Those goals are related to agro-ecological, environmental and socio-economic dimensions. Sustainability is a dynamic and temporal character. In absolute terms there is not an ending value because it changes as its dimensions make it. Spain is one of the main agricultural countries of the European Union both in terms of crop land and value of productions. The object of this study is to present a methodology of sustainability account to be incorporated into national statistical and to assess their performance in the course of the years. For that reason the data sources used have been the statistics of the Department of Agriculture and from others database. We presented a set of indicators of sustainability and its evaluation in a time series of at least 30 years. The trend analysis offers the evolution of the numerical values of the indicators in terms of efficiency, physical units used for a unit of product or its value in euros. The analyzed crops have been: wheat, barley, maize, sunflower, sugar beet, wine grape, olive oil, citrus, melon and tomato. Physical indicators were: land, water, energy, erosion, soil organic matter, and carbon balance; socio-economic indicators were: agricultural final production, prices, income, employment and use of fertilizers. In general, all crops increased their productive efficiency, higher in irrigated than on dry land. Spanish agricultural carbon sequestration capacity has multiplied by five in the last seventy years, as a result of the increase in the productivity of crops, in terms of total biomass and the modification of the soil management techniques. Livestock sector presents data of pork, broilers and laying hen. Those showed an improvement in efficiency and economic indicators. Overall we can say that Spanish agriculture and livestock subsector have a tendency towards sustainability, being its main threats extreme meteorological factors and the instability of todays markets.

The potential of organic fertilizers and water management to reduce N2O emissions in Mediterranean climate cropping systems. A review.

Environmental problems related to the use of synthetic fertilizers and to organic waste management have led to increased interest in the use of organic materials as an alternative source of nutrients for crops, but this is also associated with N2O emissions. There has been an increasing amount of research into the effects of using different types of fertilization on N2O emissions under Mediterranean climatic conditions, but the findings have sometimes been rather contradictory. Available information also suggests that water management could exert a high influence on N2O emissions. In this context, we have reviewed the current scientific knowledge, including an analysis of the effect of fertilizer type and water management on direct N2O emissions. A meta-analysis of compliant reviewed experiments revealed significantly lower N2O emissions for organic as opposed to synthetic fertilizers (23% reduction). When organic materials were segregated in solid and liquid, only solid organic fertilizer emissions were significantly lower than those of synthetic fertilizers (28% reduction in cumulative emissions). The EF is similar to the IPCC factor in conventionally irrigated systems (0.98% N2O-N N applied���1), but one order of magnitude lower in rainfed systems (0.08%). Drip irrigation produces intermediate emission levels (0.66%). Differences are driven by Mediterranean agro-climatic characteristics, which include low soil organic matter (SOM) content and a distinctive rainfall and temperature pattern. Interactions between environmental and management factors and the microbial processes involved in N2O emissions are discussed in detail. Indirect emissions have not been fully accounted for, but when organic fertilizers are applied at similar N rates to synthetic fertilizers, they generally make smaller contributions to the leached NO3��� pool. The most promising practices for reducing N2O through organic fertilization include: (i) minimizing water applications; (ii) minimizing bare soil; (iii) improving waste management; and (iv) tightening N cycling through N immobilization. The mitigation potential may be limited by: (i) residual effect; (ii) the long-term effects of fertilizers on SOM; (iii) lower yield-scaled performance; and (iv) total N availability from organic sources. Knowledge gaps identified in the review included: (i) insufficient sampling periods; (ii) high background emissions; (iii) the need to provide N2O EF and yield-scaled EF; (iv) the need for more research on specific cropping systems; and (v) the need for full GHG balances. In conclusion, the available information suggests a potential of organic fertilizers and water-saving practices to mitigate N2O emissions under Mediterranean climatic conditions, although further research is needed before it can be regarded as fully proven, understood and developed.

Hacia un Plano de Directrices Territoriales y Urban��sticas como instrumento esencial para la Habitabilidad B��sica

La habitabilidad precaria (HaP) constituye hoy el primer problema mundial del urbanismo, la ordenaci��n del territorio y varias otras disciplinas, como la arquitectura y varias ingenier��as que, en conjunto, estructuran e impulsan el sector de la construcci��n mundial que se centra en atender el alojamiento humano en su diversidad de funciones. En la Conferencia Habitat II, celebrada en 1996 en Estambul, ante el desmesurado crecimiento cuantitativo de la HaP mundial, se plante�� la prioridad de prevenir el problema de los nuevos asentamientos precarios: ���paliar los problemas relacionados con los asentamientos humanos espont��neos mediante programas y pol��ticas que se anticipen a los asentamientos no planeados���1, sin embargo, tras casi veinte a��os, a��n no existe una herramienta sustantiva y espec��fica que facilite a los pol��ticos responsables de gestionar el desarrollo urbano en ciudades con bajos recursos de pa��ses en desarrollo, tomar decisiones que transformen de la forma m��s eficiente posible el fen��meno de la proliferaci��n de asentamientos informales en una oportunidad de progreso y prosperidad para sus ciudades. La presente tesis parte de la convicci��n, que trata de fundamentar objetivamente a lo largo del desarrollo de su documentaci��n, de que dicha herramienta fundamental ha de buscarse, a partir de la teor��a Habitabilidad B��sica, como un soporte esencial con el que reconducir los futuros procesos de ocupaci��n espont��nea periurbana. El prop��sito de la investigaci��n se concreta en caracterizar, y conocer la ��ptima aplicabilidad, de un instrumento operativo elemental que ayude en la toma de decisiones estrat��gicas de las autoridades responsables sobre la mejor ubicaci��n de los asentamientos que, hasta la existencia y aplicabilidad de este instrumento, se consideran espont��neos. Asentamientos espont��neos ��stos que, en condiciones normales quedar��an sujetos durante a��os a la precariedad mientras que por medio de tal instrumento abandonar��an su g��nesis espont��nea para acceder a trav��s de planificaci��n elemental a condiciones de Habitabilidad B��sica. La materializaci��n concreta de esta herramienta ser��a un plano sint��tico de directrices de ordenaci��n territorial y urbana denominado Plano de Elecci��n del Sitio (PES). Dise��ado como un Modelo Te��rico Elemental, su aplicaci��n estar��a preferentemente orientada a ciudades peque��as de pa��ses en desarrollo que presenten escaso nivel institucional, limitada capacidad econ��mica y t��cnica, as�� como ausencia o ineficacia en su planeamiento. A trav��s de un proceso de investigaci��n basado en: la mencionada teor��a de la Habitabilidad B��sica, la literatura cient��fica de la materia y las experiencias de casos recientes de planificaci��n urbana mediante la aplicaci��n de sistemas de informaci��n del suelo, se propone una caracterizaci��n y aplicabilidad preliminar de la herramienta. Tras analizar pormenorizadamente sus fortalezas y debilidades y contando con la participaci��n de un grupo de expertos independientes, el trabajo concluye con una nueva caracterizaci��n de la herramienta y la reformulaci��n de la hip��tesis inicial. ABSTRACT Nowadays, the precarious habitability (PHa) is the main problem of urbanism around the world, land-use planning and several other disciplines such as architecture and different engineering studies that, as a whole, structure and boost the global construction sector which focuses on meeting the Human accommodation in its functional diversity. In the Habitat II Conference in Istanbul in 1996, in light of the excessive quantitative growth of the global PHa, the priority of preventing the problem of new squatter settlements was raised: "to alleviate the problems related to spontaneous human settlements through programs and policies that anticipate unplanned settlements"2, however, after nearly twenty years, there is still no substantive and specific tool to facilitate policy makers to manage urban development for towns with low-income in developing countries, taking decisions that transform as efficiently as possible the phenomenon of the proliferation of informal settlements into an opportunity for progress and prosperity for their cities. This thesis is based on the conviction, which tries to objectively substantiate along the development of its documentation, that this fundamental tool has to be sought from the Basic Habitability theory as an essential support to redirect the future processes of peri-urban spontaneous occupation. The purpose of the research is carried out to characterize, and know the optimum applicability of a basic operational tool to assist in the strategic decisions making of the responsible authorities on the best location of settlements that, until the existence and applicability of this instrument, are considered spontaneous. Spontaneous settlements which, under normal conditions would be subject to the precariousness for years while under that instrument they would abandon their spontaneous genesis for accessing by elemental planning to the Basic Habitability. The concretionary materialization of this tool would be a synthetic guidelines plan of territorial and urban planning called Site Election Plan (SEP). Designed as a Elementary Theoretical Model, its application would preferably be oriented for small towns in developing countries that represent a low institutional, economic and technical limited capacity, as well as the absence or ineffectiveness in their planning. Throughout a research process based on: the aforementioned theory of Basic Habitability, the scientific literature of the subject and the experiences of recent cases of urban planning through the application of soil information systems, characterization and preliminary applicability of the tool is proposed. After attentively analyzing their strengths and weaknesses and with the participation of a group of independent experts, the paper concludes with a new characterization of the tool and the reformulation of the initial hypothesis.

Geometrical characterization of undisturbed soil samples using X-ray computed tomography image analysis. Effect of soil management on soil structure

El estudio de la estructura del suelo es de vital importancia en diferentes campos de la ciencia y la tecnolog��a. La estructura del suelo controla procesos f��sicos y biol��gicos importantes en los sistemas suelo-planta-microorganismos. Estos procesos est��n dominados por la geometr��a de la estructura del suelo, y una caracterizaci��n cuantitativa de la heterogeneidad de la geometr��a del espacio poroso es beneficiosa para la predicci��n de propiedades f��sicas del suelo. La tecnolog��a de la tomograf��a computerizada de rayos-X (CT) nos permite obtener im��genes digitales tridimensionales del interior de una muestra de suelo, proporcionando informaci��n de la geometr��a de los poros del suelo y permitiendo el estudio de los poros sin destruir las muestras. Las t��cnicas de la geometr��a fractal y de la morfolog��a matem��tica se han propuesto como una poderosa herramienta para analizar y cuantificar caracter��sticas geom��tricas. Las dimensiones fractales del espacio poroso, de la interfaz poro-s��lido y de la distribuci��n de tama��os de poros son indicadores de la complejidad de la estructura del suelo. Los funcionales de Minkowski y las funciones morfol��gicas proporcionan medios para medir caracter��sticas geom��tricas fundamentales de los objetos geom��tricos tridimensionales. Esto es, volumen, superficie, curvatura media de la superficie y conectividad. Las caracter��sticas del suelo como la distribuci��n de tama��os de poros, el volumen del espacio poroso o la superficie poro-solido pueden ser alteradas por diferentes practicas de manejo de suelo. En este trabajo analizamos im��genes tomogr��ficas de muestras de suelo de dos zonas cercanas con practicas de manejo diferentes. Obtenemos un conjunto de medidas geom��tricas, para evaluar y cuantificar posibles diferencias que el laboreo pueda haber causado en el suelo. ABSTRACT The study of soil structure is of vital importance in different fields of science and technology. Soil structure controls important physical and biological processes in soil-plant-microbial systems. Those processes are dominated by the geometry of soil pore structure, and a quantitative characterization of the spatial heterogeneity of the pore space geometry is beneficial for prediction of soil physical properties. The technology of X-ray computed tomography (CT) allows us to obtain three-dimensional digital images of the inside of a soil sample providing information on soil pore geometry and enabling the study of the pores without disturbing the samples. Fractal geometry and mathematical morphological techniques have been proposed as powerful tools to analyze and quantify geometrical features. Fractal dimensions of pore space, pore-solid interface and pore size distribution are indicators of soil structure complexity. Minkowski functionals and morphological functions provide means to measure fundamental geometrical features of three-dimensional geometrical objects, that is, volume, boundary surface, mean boundary surface curvature, and connectivity. Soil features such as pore-size distribution, pore space volume or pore-solid surface can be altered by different soil management practices. In this work we analyze CT images of soil samples from two nearby areas with contrasting management practices. We performed a set of geometrical measures, some of them from mathematical morphology, to assess and quantify any possible difference that tillage may have caused on the soil.

Geotechnical Analysis of Contaminated Sand by Light Non-Aquous Phase Liquids

Contaminated soil reuse was investigated, with higher profusion, throughout the early 90���s, coinciding with the 1991 Gulf War, when efforts to amend large crude oil releases began in geotechnical assessment of contaminated soils. Isolated works referring to geotechnical testing with hydrocarbon ground contaminants are described in the state-of-the-art, which have been extended to other type of contaminated soil references. Contaminated soils by light non-aquous phase liquids (LNAPL) bearing capacity reduction has been previously investigated from a forensic point of view. To date, all the research works have been published based on the assumption of constant contaminant saturation for the entire soil mass. In contrast, the actual LNAPLs distribution plumes exhibit complex flow patterns which are subject to physical and chemical changes with time and distance travelled from the release source. This aspect has been considered along the present text. A typical Madrid arkosic soil formation is commonly known as Miga sand. Geotechnical tests have been carried out, with Miga sand specimens, in incremental series of LNAPL concentrations in order to observe the soil engineering properties variation due to a contamination increase. Results are discussed in relation with previous studies and as a matter of fact, soil mechanics parameters change in the presence of LNAPL, showing different tendencies according to each test and depending on the LNAPL content, as well as to the specimen���s initially planned relative density, dense or loose. Geotechnical practical implications are also commented on and analyzed. Variation on geotechnical properties may occur only within the external contour of contamination distribution plume. This scope has motivated the author to develop a physical model based on transparent soil technology. The model aims to reproduce the distribution of LNAPL into the ground due to an accidental release from a storage facility. Preliminary results indicate that the model is a potentially complementary tool for hydrogeological applications, site-characterization and remediation treatment testing within the framework of soil pollution events. A description of the test setup of an innovative three dimensional physical model for the flow of two or more phases, in porous media, is presented herein, along with a summary of the advantages, limitations and future applications for modeling with transparent material. En los primeros a��os de la d��cada de los a��os 90, del siglo pasado, coincidiendo con la Guerra del Golfo en 1991, se investig�� intensamente sobre la reutilizaci��n de suelos afectados por grandes vol��menes de vertidos de crudo, foment��ndose la evaluaci��n geot��cnica de los suelos contaminados. Se describen, en el estado del arte de esta t��sis, una serie de trabajos aislados en relaci��n con la caracterizaci��n geot��cnica de suelos contaminados con hidrocarburos, descripci��n ampliada mediante referencias relacionadas con otros tipos de contaminaci��n de suelos. Existen estudios previos de patolog��a de cimentaciones que analizan la reducci��n de la capacidad portante de suelos contaminados por hidrocarburos l��quidos ligeros en fase no acuosa (acr��nimo en ingl��s: LNAPL de ���Liquid Non-Aquous Phase Liquid���). A fecha de redacci��n de la tesis, todas las publicaciones anteriores estaban basadas en la consideraci��n de una saturaci��n del contaminante constante en toda la extensi��n del terreno de cimentaci��n. La distribuci��n real de las plumas de contaminante muestra, por el contrario, complejas trayectorias de flujo que est��n sujetas a cambios f��sico-qu��micos en funci��n del tiempo y la distancia recorrida desde su origen de vertido. ��ste aspecto ha sido considerado y tratado en el presente texto. La arena de Miga es una formaci��n geol��gica t��pica de Madrid. En el ��mbito de esta tesis se han desarrollado ensayos geot��cnicos con series de muestras de arena de Miga contaminadas con distintas concentraciones de LNAPL con el objeto de estimar la variaci��n de sus propiedades geot��cnicas debido a un incremento de contaminaci��n. Se ha realizado una evaluaci��n de resultados de los ensayos en comparaci��n con otros estudios previamente analizados, resultando que las propiedades mec��nicas del suelo, efectivamente, var��an en funci��n del contenido de LNAPL y de la densidad relativa con la que se prepare la muestra, densa o floja. Se analizan y comentan las implicaciones de car��cter pr��ctico que supone la mencionada variaci��n de propiedades geot��cnicas. El autor ha desarrollado un modelo f��sico basado en la tecnolog��a de suelos transparentes, considerando que las variaciones de propiedades geot��cnicas ��nicamente deben producirse en el ��mbito interior del contorno de la pluma contaminante. El objeto del modelo es el de reproducir la distribuci��n de un LNAPL en un terreno dado, causada por el vertido accidental de una instalaci��n de almecenamiento de combustible. Los resultados preliminares indican que el modelo podr��a emplearse como una herramienta complementaria para el estudio de eventos contaminantes, permitiendo el desarrollo de aplicaciones de car��cter hidrogeol��gico, caracterizaci��n de suelos contaminados y experimentaci��n de tratamientos de remediaci��n. Como aportaci��n de car��cter innovadora, se presenta y describe un modelo f��sico tridimensional de flujo de dos o m��s fases a trav��s de un medio poroso transparente, analiz��ndose sus ventajas e inconvenientes as�� como sus limitaciones y futuras aplicaciones.

Determination of the average ionization and thermodynamic regimes of xenon plasmas with an application to the characterization of blast waves launched in xenon clusters

Radiative shock waves play a pivotal role in the transport energy into the stellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible laboratory conditions and their study has been highlighted as an area requiring further experimental investigations. Low density material with high atomic mass is suitable to achieve radiative regime, and, therefore, low density xenon gas is commonly used for the medium in which the radiative shock propagates. In this work the averageionization and the thermodynamicregimes of xenonplasmas are determined as functions of the matter density and temperature in a wide range of plasma conditions. The results obtained will be applied to characterize blastwaveslaunched in xenonclusters

Soil compaction and vegetation cover in a Scots pine stand at the Mediterranean rangelands

Right development of ROOT SYSTEMS is essential to ensure seedling survival in the initial stages of natural regeneration processes. Soil compaction determines this development both because of its influence on soil T�� & moisture dynamics and for its direct effect on soil mechanical impedance to root growth. All this effects can be assessed as a whole through soil penetration resistance (Soil Strength) measurements. SOIL STRENGTH has been usually evaluated in forest research in connection with severe disturbances derived from heavy machinery works during forest operations. Nevertheless, undisturbed soils are also expected to show different levels of compaction for root development. Organic matter modifies soil structure and so on porosity, compaction and resultant soil resistance to penetration. Its concentration in surface layers is rather related to vegetation cover composition and density. So within forest stands, a relationship is expected to be found between VEGETATION COVER density and compaction measured as resistance to penetration (soil strength)

Assessment of oral bioaccessibility of arsenic in playground soil in Madrid (Spain): A three-method comparison and implications for risk assessment

Three methodologies to assess As bioaccessibility were evaluated using playgroundsoil collected from 16 playgrounds in Madrid, Spain: two (Simplified Bioaccessibility Extraction Test: SBET, and hydrochloric acid-extraction: HCl) assess gastric-only bioaccessibility and the third (Physiologically Based Extraction Test: PBET) evaluates mouth–gastric–intestinal bioaccessibility. Aqua regia-extractable (pseudo total) As contents, which are routinely employed in riskassessments, were used as the reference to establish the following percentages of bioaccessibility: SBET – 63.1; HCl – 51.8; PBET – 41.6, the highest values associated with the gastric-only extractions. For Madridplaygroundsoils – characterised by a very uniform, weakly alkaline pH, and low Fe oxide and organic matter contents – the statistical analysis of the results indicates that, in contrast with other studies, the highest percentage of As in the samples was bound to carbonates and/or present as calcium arsenate. As opposed to the As bound to Fe oxides, this As is readily released in the gastric environment as the carbonate matrix is decomposed and calcium arsenate is dissolved, but some of it is subsequently sequestered in unavailable forms as the pH is raised to 5.5 to mimic intestinal conditions. The HCl extraction can be used as a simple and reliable (i.e. low residual standard error) proxy for the more expensive, time consuming, and error-prone PBET methodology. The HCl method would essentially halve the estimate of carcinogenic risk for children playing in Madridplaygroundsoils, providing a more representative value of associated risk than the pseudo-total concentrations used at present

Spectral-analysis-surface-waves-method in ground characterization

The prediction of train induced vibration levels in structures close to railway tracks before track construction starts is important in order to avoid having to implement costly mitigation measures afterwards. The used models require an accurate characterization of the propagation medium i.e. the soil layers. To this end the spectral analysis of surface waves (SASW) method has been chosen among the active surface waves techniques available. As dynamic source a modal sledge hammer has been used. The generated vibrations have been measured at known offsets by means of several accelerometers. There are many parameters involved in estimating the experimental dispersion curve and, later on, thickness and propagation velocities of the different layers. Tests have been carried out at the Segovia railway station. Its main building covers some of the railway tracks and vibration problems in the building should be avoided. In the paper these tests as well as the influence of several parameters on the estimated soil profile will be detailed.

Community Structure in Soil Porous System

Diffusion controls the gaseous transport process in soils when advective transport is almost null. Knowledge of the soil structure and pore connectivity are critical issues to understand and modelling soil aeration, sequestration or emission of greenhouse gasses, volatilization of volatile organic chemicals among other phenomena. In the last decades these issues increased our attention as scientist have realize that soil is one of the most complex materials on the earth, within which many biological, physical and chemical processes that support life and affect climate change take place. A quantitative and explicit characterization of soil structure is difficult because of the complexity of the pore space. This is the main reason why most theoretical approaches to soil porosity are idealizations to simplify this system. In this work, we proposed a more realistic attempt to capture the complexity of the system developing a model that considers the size and location of pores in order to relate them into a network. In the model we interpret porous soils as heterogeneous networks where pores are represented by nodes, characterized by their size and spatial location, and the links representing flows between them. In this work we perform an analysis of the community structure of porous media of soils represented as networks. For different real soils samples, modelled as heterogeneous complex networks, spatial communities of pores have been detected depending on the values of the parameters of the porous soil model used. These types of models are named as Heterogeneous Preferential Attachment (HPA). Developing an exhaustive analysis of the model, analytical solutions are obtained for the degree densities and degree distribution of the pore networks generated by the model in the thermodynamic limit and shown that the networks exhibit similar properties to those observed in other complex networks. With the aim to study in more detail topological properties of these networks, the presence of soil pore community structures is studied. The detection of communities of pores, as groups densely connected with only sparser connections between groups, could contribute to understand the mechanisms of the diffusion phenomena in soils.

The relationship between soil geochemistry and the bioaccessibility of trace elements in playground soil

A total of 32 samples of surficial soil were collected from 16 playground areas in Madrid (Spain), in order to investigate the importance of the geochemistry of the soil on subsequent bioaccessibility of trace elements. The in vitro bioaccessibility of As, Co, Cr, Cu, Ni, Pb and Zn was evaluated by means of two extraction processes that simulate the gastric environment and one that reproduces a gastric + intestinal digestion sequence. The results of the in vitro bioaccessibility were compared against aqua regia extractions (���total��� concentration), and it was found that total concentrations of As, Cu, Pb and Zn were double those of bioaccessible values, whilst that of Cr was ten times higher. Whereas the results of the gastric + intestinal extraction were affected by a high uncertainty, both gastric methods offered very similar and consistent results, with bioaccessibilities following the order: As = Cu = Pb = Zn > Co > Ni > Cr, and ranging from 63 to 7 %. Selected soil properties including pH, organic matter, Fe and CaCO3 content were determined to assess their influence on trace element bioaccessibility, and it was found that Cu, Pb and Zn were predominantly bound to organic matter and, to a lesser extent, Fe oxides. The former fraction was readily accessible in the gastric solution, whereas Fe oxides seemed to recapture negatively charged chloride complexes of these elements in the gastric solution, lowering their bioaccessibility. The homogeneous pH of the playground soils included in the study does not influence trace element bioaccessibility to any significant extent except for Cr, where the very low gastric accessibility seems to be related to the strongly pH-dependent formation of complexes with organic matter. The results for As, which have been previously described and discussed in detail in Mingot et al. (Chemosphere 84: 1386–1391, 2011), indicate a high gastric bioaccessibility for this element as a consequence of its strong association with calcium carbonate and the ease with which these bonds are broken in the gastric solution. The calculation of risk assessments are therefore dependant on the methodology used and the specific environment they address. This has impacts on management strategies formulated to ensure that the most vulnerable of society, children, can live and play without adverse consequences to their health.