Coupled human and natural system dynamics as key to the sustainability of Lake Victoria's ecosystem services

East Africa���s Lake Victoria provides resources and services to millions of people on the lake���s shores and abroad. In particular, the lake���s fisheries are an important source of protein, employment, and international economic connections for the whole region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out piecemeal on different aspects of Lake Victoria���s system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a whole. We did so by first building a qualitative model of the lake���s social-ecological system. We then investigated the model system through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks��� vulnerability to exploitation but reduce society���s vulnerability to variability in individual stocks. We describe how there are multiple pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a paving stone for future quantitative analyses of system dynamics at local scales.

Narrow dust jets in a diffuse gas coma: a natural product of small active regions on comets

Comets often display narrow dust jets but more diffuse gas comae when their eccentric orbits bring them into the inner solar system and sunlight sublimates the ice on the nucleus. Comets are also understood to have one or more active areas covering only a fraction of the total surface active with sublimating volatile ices. Calculations of the gas and dust distribution from a small active area on a comet���s nucleus show that as the gas moves out radially into the vacuum of space it expands tangentially, filling much of the hemisphere centered on the active region. The dust dragged by the gas remains more concentrated over the active area. This explains some puzzling appearances of comets having collimated dust jets but more diffuse gaseous atmospheres. Our test case is 67P/Churyumov���Gerasimenko, the Rosetta mission target comet, whose activity is dominated by a single area covering only 4% of its surface.

Gas monitoring methodology and application to CCS projects as defined by atmospheric and remote sensing survey in the natural analogue of Campo de Calatrava

CO2 capture and storage (CCS) projects are presently developed to reduce the emission of anthropogenic CO2 into the atmosphere. CCS technologies are expected to account for the 20% of the CO2 reduction by 2050. Geophysical, ground deformation and geochemical monitoring have been carried out to detect potential leakage, and, in the event that this occurs, identify and quantify it. This monitoring needs to be developed prior, during and after the injection stage. For a correct interpretation and quantification of the leakage, it is essential to establish a pre-injection characterization (baseline) of the area affected by the CO2 storage at reservoir level as well as at shallow depth, surface and atmosphere, via soil gas measurements. Therefore, the methodological approach is important because it can affect the spatial and temporal variability of this flux and even jeopardize the total value of CO2 in a given area. In this sense, measurements of CO2 flux were done using portable infrared analyzers (i.e., accumulation chambers) adapted to monitoring the geological storage of CO2, and other measurements of trace gases, e.g. radon isotopes and remote sensing imagery were tested in the natural analogue of Campo de Calatrava (Ciudad Real, Spain) with the aim to apply in CO2 leakage detection; thus, observing a high correlation between CO2 and radon (r=0,858) and detecting some vegetation indices that may be successfully applied for the leakage detection.

Tanque a��reo de almacenamiento de gas natural licuado de tipo membrana y 200.000 m3 de volumen

El presente proyecto consiste en el dise��o b��sico de ingenier��a de un tanque a��reo de almacenamiento de gas natural licuado (GNL) de integridad total con tecnolog��a de membrana y con una capacidad neta de almacenamiento de 200 000 m3 a una temperatura de -162��C y una presi��n m��xima de 15 kPa. El proyecto desarrolla los siguientes puntos: el dise��o del tanque interno con tecnolog��a de membrana, dimensionamiento del aislante, dise��o del techo suspendido, tanque externo, c��pula de hormig��n, cimentaci��n, dimensionamiento de los equipos, Ensayos, puesta en fr��o, puesta en servicio, planificaci��n de la ejecuci��n del proyecto, recursos empleados, control de la presi��n, prevenci��n del rollover, coste del tanque y an��lisis econ��mico del proyecto

Estaci��n de servicio de gas natural licuado y comprimido para veh��culos

Se propone la construcci��n de una planta sat��lite de gas natural anexa a una estaci��n de servicio de carburante. El inter��s del proyecto se centra en el ahorro econ��mico que supone el uso de este combustible para el transporte por carretera (hasta 50 %). Adem��s el gas natural es, en relaci��n al petr��leo, m��s limpio y la relaci��n reservas/producci��n es mayor. En Espa��a la infraestructura de esta tecnolog��a es una de las mayores y mejor consolidadas de Europa. Se ha elegido la E.S. localizada en el km 26 de la autopista A1 con sentido Burgos (San Sebasti��n de los Reyes, Madrid). Esta autopista es una de las principales v��as de conexi��n entre Espa��a y el resto de Europa, resultando interesante pensando en el sector trasportista. La planta dispondr�� de un tanque criog��nico de 60 m3 para almacenar gas natural licuado (GNL) a una temperatura de -163 ��C. Parte de ��ste ser�� comprimido a 290 bar y despu��s conducido a un vaporizador ambiental de alta presi��n que lo gasificar��. Finalmente el gas resultante se odorizar�� obteniendo gas natural comprimido (GNC) que quedar�� preparado para su almacenaje en vasijas. El tanque criog��nico (GNL) y las botellas (GNC) se conectar��n a sus respectivos surtidores para el suministro de combustible. La planta incluir�� un surtidor de GNC y otro de GNL para veh��culos pesados. Se realizar�� el montaje e instalaci��n de los equipos y l��neas necesarios para el almacenaje, manipulaci��n y suministro de gas natural vehicular.

Dise��o del Tren de Licuaci��n Conoco Phillips de 5 MTPA de Capacidad en Planta Bidireccional de Gas Natural

Dise��o de un tren de licuaci��n Conoco Phillips de 5 MTPA, mediante el software de simulaci��n Aspen Plus. Incluye planificaci��n y an��lisis econ��mico del proyecto.

An��lisis de las tecnolog��as de accionamiento en la compresi��n del gas natural y su aplicaci��n a una estaci��n de compresi��n

Este proyecto consiste en el an��lisis de las t��cnicas de compresi��n de gas natural, tanto t��cnica como econ��micamente, as�� como el dise��o de la estaci��n de compresi��n localizada en Ir��n, provincia de Guip��zcoa, con la mejor opci��n. El proyecto define el inter��s de este tipo de instalaciones, su funcionamiento, detalla los distintos sistemas de los que consta la estaci��n de compresi��n y estudia la rentabilidad econ��mica en base al presupuesto de la instalaci��n y a la retribuci��n de las actividades reguladas del sector gasista. Los distintos sistemas de los que consta la estaci��n de compresi��n, y que forman parte del contenido del proyecto son, todos los necesarios para el funcionamiento de la estaci��n: sistemas mec��nicos, instrumentaci��n y control, obra civil y sistemas auxiliares (sistemas el��ctricos, de seguridad y antiintrusi��n).

Tuber��as de Gas Natural para alimentaci��n de la planta Gorgon LNG a partir del yacimiento Gorgon

Este trabajo tiene como objetivo el dise��o y dimensionamiento del gasoducto de alimentaci��n a la planta de producci��n de GNL del proyecto Gorgon LNG, el cual consiste en la explotaci��n de varios yacimientos de gas natural offshore al oeste de Australia y la producci��n de GNL en la planta situada en la Isla Barrow. Se han considerado dos fases de desarrollo, una inicial con ocho pozos, y otra de madurez con doce. El dimensionamiento se ha realizado mediante simulaciones con el programa Aspen Hysys, mediante el cual se han obtenido los di��metros internos m��nimos y los perfiles de presiones y temperaturas, as�� como el caudal de MEG requerido para evitar la formaci��n de hidratos. Posteriormente, mediante c��lculo matem��tico se ha calculado el espesor teniendo en cuenta las tensiones mec��nicas a las que estar�� sometida la tuber��a. Finalmente, a partir de los resultados del c��lculo t��cnico se ha realizado el estudio econ��mico, estimando costes e ingresos, en el cual se ha realizado un estudio de la rentabilidad del proyecto y un an��lisis de sensibilidad, resultando un proyecto t��cnica y econ��micamente viable.

Radiactividad natural de los materiales de construcci��n. Aplicaci��n al hormig��n. Parte II. Radiaci��n interna: el gas rad��n

El presente art��culo analiza aspectos relacionados con los tipos de radiactividad natural presentes en el interior de las edificaciones, sus fuentes y sus influencias. M��s concretamente, desarrolla el estudio de la radiactividad ambiental en el interior de los espacios construidos debida a la presencia del gas rad��n, as�� como sus fuentes de origen y los niveles recomendados. Este es un art��culo que se presenta como la segunda parte de un trabajo sobre radiactividad natural en los materiales de construcci��n, cuya primera parte hace referencia a la radiaci��n externa de dichos materiales y se publica por los mismos autores, en esta misma revista. Al mismo tiempo, se realiza un recorrido por el marco normativo, tanto internacional como nacional, relativo al rad��n y a sus descendientes de vida media corta. El presente trabajo es parte de la tesis doctoral de la primera autora del mismo, Beatriz Piedecausa Garc��a, a quien el resto de autores agradece su esfuerzo para preparar el texto que ahora se publica y la autorizaci��n y las facilidades ofrecidas para acceder a su trabajo.

Alteration of natural �����Ar activity concentration in the subsurface by gas transport and water infiltration

High �����Ar activity concentration in soil gas is proposed as a key evidence for the detection of underground nuclear explosion by the Comprehensive Nuclear Test-Ban Treaty. However, such a detection is challenged by the natural background of �����Ar in the subsurface, mainly due to Ca activation by cosmic rays. A better understanding and improved capability to predict �����Ar activity concentration in the subsurface and its spatial and temporal variability is thus required. A numerical model integrating �����Ar production and transport in the subsurface is developed, including variable soil water content and water infiltration at the surface. A parameterized equation for �����Ar production in the first 15 m below the surface is studied, taking into account the major production reactions and the moderation effect of soil water content. Using sensitivity analysis and uncertainty quantification, a realistic and comprehensive probability distribution of natural �����Ar activity concentrations in soil gas is proposed, including the effects of water infiltration. Site location and soil composition are identified as the parameters allowing for a most effective reduction of the possible range of �����Ar activity concentrations. The influence of soil water content on �����Ar production is shown to be negligible to first order, while �����Ar activity concentration in soil gas and its temporal variability appear to be strongly influenced by transient water infiltration events. These results will be used as a basis for practical CTBTO concepts of operation during an OSI.