Spatial distribution of morphometric parameters of glacial cirques in the Central Pyrenees(Aran and Boí valleys)

Glacial cirques are typical landscape features of mid-latitude mountain environments like the Central Pyrenees. Their morphology as well as their spatial distribution provides insights about past glaciers and climates. In this study, we examine the distribution, morphometrical and topographical characteristics of glacial cirques in two U-shaped glacial valleys located in the Central Pyrenees – the Aran and the Boí valleys. They are located in different aspects of this mountain range(north vs south) under different climatic influences that promoted distinct glaciation patterns during the late Pleistocene. The spatial mapping of these landforms was carried out using high-resolution imagery and field observations. We analysed the data of the morphometrical and topographical variables of the glacial cirques by using different statistical and geospatial methods in order tounveil the factors controlling their formation and development. A total of 186 glacial cirques were mapped in the study area, including 119 in the Aran and 67 in the Boí valleys. The local topography and microclimate conditions lead to substantial differences in both areas in terms of the morphology and dimensions of the cirques. Glacial cirques in Boí are distributed at slightly higher elevations than in Aran and they are also larger, though their dimensions decrease with elevation in both valleys. Aran cirques are mostly oriented NE, while Boí landforms do not show any prevailing aspect. Even though lithology does not control the distribution of the glacial cirques, some specific lithological settings may favour the development of larger cirques. In general, glacial cirques in the Aran and the Boí valleys show morphometrical properties similar to those reported in other mid-latitude mountain ranges.     

Benchmarking of two three-dimensional numerical models in time/space domain to predict railway-induced ground vibrations

In the last 30 years,the scientific community has developed and proposed different models and numerical approaches for the study of vibrations induced by railway traffic.Most of them are formulated in the frequency/wave number domain and with a 2.5D approach.Three-dimensional numerical models formulated in the time/space domain are less frequently used,mainly due to their high computational cost.Notwithstanding,these models present very attractive characteristics,such as the possibility of considering nonlinear behaviors or the modelling of excess pore pressure and non-homogeneous and non-periodic geometries in the longitudinal direction of the track.In this study,two 3D numerical approaches formulated in the time/space domain are compared and experimentally validated.The first one consists of a finite element approach and the second one of a finite difference approach.The experimental validation in an actual case situated in Carregado(Portugal)shows an acceptable fitting between the numerical results and the actual measurements for both models.However,there are some differences among them.This study therefore includes some recommendations for their use in practical soil dynamics and geotechnical engineering.     

Nutrient Behavior and Productivity in a River System Affected by Fishpond Effluents

The expanding culture of fish in coastal areas has raised issues concerning resource use conflicts and water quality problems. A major concern is pollution resulting from nitrogen and phosphorus lost to the environment from feed wastage and fish excretion. The purpose of the study was to assess the environmental conditions in a river system affected by fishponds. Nutrient fluxes and productivity measurements were obtained from Sta. Rita River, a river estuary used as a discharge and an irrigation area of approximately 316 ha of fishponds. During the dry season, when freshwater influence is absent, salinity values inside the river were higher than outside (in the bay). Nutrient trends during ebb and flood periods were similar except for some lag in the profiles that indicate tidal oscillation. The absence of river flow during the dry period resulted in a negligible flux of nutrients along the river. During the wet season, the increase in nitrate concentrations indicates river inputs while the decrease in phosphate values imply less of freshwater influence but more from ponds and domestic wastes. Similarity in productivity estimates signifies good agreement between direct and indirect methods. The absence of flushing during the dry season translates to trapping of nutrients discharged from the ponds in the drainage canals.     

Climatic trend and the retreat and disintegration of ice shelves on the Antarctic Peninsula: an overview

Observation of the retreat and disintegration of ice shelves around the Antarctic Peninsula during the last three decades and associated changes in air temperature, measured at various meteorological stations on the Antarctic Peninsula, are reviewed. The climatically induced retreat of the northern Larsen Ice Shelf on the east coast and of the Wordie, George VI, and Wilkins ice shelves on the west coast amounted to about 10 000 km² since the mid-1960s. A summary is presented on the recession history of the Larsen Ice Shelf and on the collapse of those sections north of Robertson Island in early 1995. The area changes were derived from images of various satellites, dating back to a late 1963 image from the recently declassified US Argon space missions. This photograph reveals a previously unknown, minor advance of the northern Larsen Ice Shelf before 1975. During the period of retreat a consistent and pronounced warming trend was observed at the stations on both east and west coasts of the Antarctic Peninsula, but a major cause of the fast retreat and final collapse of the northernmost sections of the Larsen Ice Shelf were several unusually warm summers. Temperature records from the nearby station Marambio show that a positive mean summer temperature was reached for the first time in 1992-93. Recent observations indicate that the process of ice shelf disintegration is proceeding further south on both sides of the Antarctic Peninsula.     

The cloud-in-cloud problem for non-Gaussian density fields

The cloud-in-cloud problem is studied in the context of the extension to non-Gaussian density fields of the PS approach for the calculation of the mass function. As an example of a non-Gaussian probability distribution function (PDF), we consider the chi-square distribution with various degrees of freedom. We generate density fields in cubic boxes with periodic boundary conditions, and then determine the number of points considered collapsed at each scale through a hierarchy of smoothing windows. We find that the mass function we obtain differs from that predicted using the extended PS formalism, particularly for low values of σ and for those PDFs that differ most from a Gaussian.     

Assessment of the conventional molybdenum-blue and magnesium-induced coprecipitation procedures in phosphorus measurement in various aquatic environments

Phosphorus (P) is an essential nutrient utilized by all organisms for energy transport and growth. Both the conventional molybdenum-blue method and the magnesium-induced coprecipitation (MAGIC) procedures were applied for the measurement of dissolved inorganic phosphorus (DIP) and total dissolved phosphorus (TDP) in more than 840 water samples collected between 2003 and 2005, including seawater (the Huanghai Sea, the East China Sea, and the northern South China Sea), water from rivers and estuaries (the Changjiang, the Huanghe, and the major rivers emptying into the Jiaozhou Bay), groundwater (in the drainage basin surrounding the Jiaozhou Bay), rain- water, and aquaculture water samples. The MAGIC method allows the investigation of phosphorus distributions and cycling for systems in which DIP is below the detection limits of conventional methods. Comparison between the two methods demonstrated that the concentrations obtained with both methods were signiˉcantly correlated. The di?erences of DIP and TDP concentrations measured with the two methods were higher when the concentrations of DIP and TDP were lower, implying the lower reproducibility at low concentrations. The concentration di?erences increase with the increase in the proportion of DOP in TDP, which indicates that the discrepancy of DIP concentrations measured with the two methods increases when the DOP concentration is high. The discrepancies indicated that the composition of P compounds di?ers depending on sample sources and water type; it would be useful to infer the presence of di?erent phosphorus compound pools from di?erences between the two methods. This study indicates the potential presence of a pool of alkaline-labile compounds for samples from rainwater and rivers and estuaries surrounding the Jiaozhou Bay; the potential presence of acid-labile compounds that were adsorbed by Mg(OH)2 for samples from the Changjiang Estuary, Huanghai Sea, East China Sea, and groundwater; the po- tential presence of a substantial pool of acid-labile compounds that were not adsorbed by Mg(OH)2 for samples from the Huanghe Estuary, aquaculture water, the East China Sea algal bloom water, and the northern South China Sea.     

Underwater measurements of carbon dioxide evolution in marine plant communities: A new method

We developed a new methodology to determine CO₂ fluxes in intertidal and shallow subtidal plant communities, namely seagrasses, both when the plants are submerged and when they are air-exposed. The apparatus comprises closed incubation chambers and a gas exchange column, designed to remove carbon dioxide from the water. Different types of incubation chambers were designed and built to adapt the system to distinct environments and incubation requirements. The methodology was tested under a comprehensive range of situations and its advantages and limitations are discussed. Overall, the method provides precise measurements of community carbon dioxide fluxes, through a fast and non-intrusive process, allowing repeatable in situ measurements of carbon uptake both in submerged and air-exposed conditions. As the experimental apparatus is identical, directly comparable measurements of air-exposed and submerged community production may be obtained, allowing sound estimates of daily carbon budgets of intertidal and shallow subtidal communities.     

地球电化学勘查法寻找不同埋深隐伏金矿的研究

隐伏金矿在宏观和微观原电池的作用下，产生电化学溶解，形成金的离子晕。在不同埋深的隐伏金矿上方，利用地球电化学勘查法能提取到这些金离子晕，从而证明利用地球化学勘查法来寻找隐伏金矿的可行性。