The role of microorganisms in the formation of calcitic moonmilk deposits and speleothems in Altamira Cave

Bacteria are able to induce carbonate precipitation although the participation of microbial or chemical processes in speleothem formation remains a matter of debate. In this study, the origin of carbonate depositions such as moonmilk, an unconsolidated microcrystalline formation with high water content, and the consolidation of carbonate precipitates into hard speleothems were analyzed. The utilized methods included measurements of the composition of stable isotopes in these precipitates, fluorimetric determinations of RNA/DNA ratios and respirometric estimations in Altamira Cave. Results from isotope composition showed increases of the δ18O and δ13C ratios from moonmilk in the very first stages of formation toward large speleothems. Estimates of RNA/DNA ratios suggested an inactivation of microorganisms from incipient moonmilk toward consolidated deposits of calcium carbonate. Respiratory activity of microorganisms also showed a significant decrease in samples with accumulated calcite. These results suggest that bacterial activity induces the conditions required for calcium carbonate precipitation, initiating the first stages of deposition. Progressive accumulation of carbonate leads towards a less favorable environment for the development of bacteria. On consolidated speleothems, the importance of bacteria in carbonate deposition decreases and chemical processes gain importance in the deposition of carbonates.

Spatiotemporal characteristics of the Huangtupo landslide in the Three Gorges region (China) constrained by radar interferometry

The Huangtupo landslide is one of the largest in the Three Gorges region, China. The county-seat town of Badong, located on the south shore between the Xiling and Wu gorges of the Yangtze River, was moved to this unstable slope prior to the construction of the Three Gorges Project, since the new Three Gorges reservoir completely submerged the location of the old city. The instability of the slope is affecting the new town by causing residential safety problems. The Huangtupo landslide provides scientists an opportunity to understand landslide response to fluctuating river water level and heavy rainfall episodes, which is essential to decide upon appropriate remediation measures. Interferometric Synthetic Aperture Radar (InSAR) techniques provide a very useful tool for the study of superficial and spatially variable displacement phenomena. In this paper, three sets of radar data have been processed to investigate the Huangtupo landslide. Results show that maximum displacements are affecting the northwest zone of the slope corresponding to Riverside slumping mass I#. The other main landslide bodies (i.e. Riverside slumping mass II#, Substation landslide and Garden Spot landslide) exhibit a stable behaviour in agreement with in situ data, although some active areas have been recognized in the foot of the Substation landslide and Garden Spot landslide. InSAR has allowed us to study the kinematic behaviour of the landslide and to identify its active boundaries. Furthermore, the analysis of the InSAR displacement time-series has helped recognize the different displacement patterns on the slope and their relationships with various triggering factors. For those persistent scatterers, which exhibit long-term displacements, they can be decomposed into a creep model (controlled by geological conditions) and a superimposed recoverable term (dependent on external factors), which appears closely correlated with reservoir water level changes close to the river's edge. These results, combined with in situ data, provide a comprehensive analysis of the Huangtupo landslide, which is essential for its management.

Geological risk assessment of Amtoudi Agadir in southern Morocco: a key case for sustainable cultural heritage

Medieval fortified granaries known as “agadirs” are very common in southern Morocco, being catalogued as world cultural heritage by United Nations. These Berber buildings (made of stones and tree trunks) usually located on rocky promontories, constitute historical testimonials related to the origin of Morocco, and, as tourist attractions, have a positive impact on the local economy. The sustainability of these ancient monuments requires geological-risk evaluations of the massif stability under the agadir with the proposal of stabilization measures, and an architectonic analysis with appropriate maintenance of the structural elements. An interdisciplinary study including climate, seismicity, hydrology, geology, geomorphology, geotechnical surveys of the massif, and diagnosis of the degradation of structural elements have been performed on the Amtoudi Agadir, selected as a case study. The main findings from this study are that the prevalent rocks used for construction (coming from the underlying substratum) are good-quality arkosic sandstones; the SW cliffs under the agadir are unstable under water saturation; some masonry walls are too thin and lack interlocking stones and mortar; and failures in the beams (due to flexure, fracture, and exhaustion in the resistance due to insect attacks or plant roots) are common. The basic risk assessment of ancient buildings of cultural heritage and their geologic substratum are needed especially in undeveloped areas with limited capacity to implement durable conservation policies. Therefore, recommendations have been provided to ensure the stability and maintenance of this important archaeological site.

New methodology for describing the equilibrium beach profile applied to the Valencia's beaches

Mathematical models used for the understanding of coastal seabed morphology play a key role in beach nourishment projects. These projects have become the fundamental strategy for coastal maintenance during the last few years. Accordingly, the accuracy of these models is vital to optimize the costs of coastal regeneration projects. Planning of such interventions requires methodologies that do not generate uncertainties in their interpretation. A study and comparison of mathematical simulation models of the coastline is carried out in this paper, as well as elements that are part of the model that are a source of uncertainty. The equilibrium profile (EP) and the offshore limit corresponding to the depth of closure (DoC) have been analyzed taking into account different timescale ranges. The results have thus been compared using data sets from three different periods which are identified as present, past and future. Accuracy in data collection for the beach profiles and the definition of the median grain size calculation using collected samples are the two main factors that have been taken into account in this paper. These data can generate high uncertainties and can produce a lack of accuracy in nourishment projects. Together they can generate excessive costs due to possible excess or shortage of sand used for the nourishment. The main goal of this paper is the development of a new methodology to increase the accuracy of the existing equilibrium beach profile models, providing an improvement to the inputs used in such models and in the fitting of the formulae used to obtain seabed shape. This new methodology has been applied and tested on Valencia's beaches.

Uso do zoneamento ambiental do Médio Rio Grande na sub-bacia hidrográfica do Ribeirão Bocaina - Passos/MG

Este trabalho é parte integrante do Projeto Grande Minas - União pelas Águas, que realizou o Zoneamento Ambiental das Sub-bacias Hidrográficas dos Afluentes Mineiros do Médio Rio Grande. Após a obtenção dos produtos finais do zoneamento, entra-se agora, na fase de “Implementação”, ou seja, de sua aplicação direta para contribuir no processo de gestão dos recursos hídricos das sub-bacias hidrográficas da área de estudo. Neste trabalho estuda-se, especificamente, a sub-bacia hidrográfica do Ribeirão Bocaina, considerada uma das 34 sub-bacias que envolvem a Bacia Hidrográfica dos Afluentes Mineiros do Médio Rio Grande e situa-se no município de Passos-MG, possuindo uma área de 457,9 km². O trabalho busca dar uma contribuição para a gestão dos recursos hídricos nesta sub-bacia, que vem sofrendo com a degradação do seu recurso hídrico. O objetivo é disponibilizar instrumentos cartográficos para subsidiar a gestão dos recursos hídricos e, com isto, contribuir com a sua preservação e uso sustentável. A sistemática metodológica envolve uma análise dos aspectos legais da área de estudo; a construção de um Banco de Dados Digital georreferenciado com informações sobre os meios físico, biótico e socioeconômico da sub-bacia e a produção de uma carta derivada, de cunho interpretativo e de fácil leitura, que possa ser utilizada diretamente pelo gestor público nas tomadas de decisões. A base digital produzida conta com uma série de mapas digitais, dentre eles: mapas climáticos, de solos, declividades, geomorfológico, geológico, de sistemas aquíferos, hidrográfico, uso e ocupação do solo. Com relação à carta derivada, destaca os terrenos que apresentam maior predisposição à alterações diretas nos recursos hídricos.