Helder I. Chaminé

Enigmatic reticulated filaments in subsurface granite.

In the last few years, geomicrobiologists have focused their researches on the nature and origin of enigmatic reticulated filaments reported in modern and fossil samples from limestone caves and basalt lava tubes. Researchers have posed questions on these filaments concerning their nature, origin, chemistry, morphology, mode of formation and growth. A tentative microbial origin has been elusive since these filaments are found as hollow tubular sheaths and could not be affiliated to any known microorganism. We describe the presence of similar structures in a 16th century granite tunnel in Porto, Northwest Portugal. The reticulated filaments we identify exhibit fine geometry surface ornamentation formed by cross-linked Mn-rich nanofibres, surrounded by a large amount of extracellular polymeric substances. Within these Mn-rich filaments we report for the first time the occurrence of microbial cells.

Prograde epizonal clay mineral assemblages and retrograde alteration in tectonic basins controlled by major strike-slip zones (W Iberian Variscan chain)

Abstract We have carried out optical microscopy, X-ray diffraction (XRD) and scanning and transmission electron microscopy (SEM and TEM) studies of phyllosilicates from black slates of very low to low-grade metamorphism. Such slates belong to a Middle/Late Devonian basin and an Early Carboniferous basin associated with the Porto-Tomar-Ferreira do Alentejo strike-slip shear zone (Ossa-Morena Zone, Portuguese Iberian Variscan Massif). These black slates are imbricated in an Upper Proterozoic substratum of higher metamorphic grade. Kübler Index values of white micas and mineral assemblages deduced from the XRD, SEM and TEM data (muscovite, chlorite and pyrophyllite) indicate high anchizonal and epizonal metamorphic conditions for slates from these basins. The b parameter and the phengitic contents of mica suggest the occurrence of low pressures (1-2 kbar) related to an extensional geotectonic setting. The dense fracture network shown by SEM images and the high density of crystal defects revealed by the TEM study in the eastern basin, adjacent to faults produced by shearing, suggest that their epizonal phyllosilicates were more affected during deformation than those belonging to the western basin, favouring the development of a retrograde association (siderite, kaolin group minerals and Al-smectite) on the epizonal paragenesis. Microcavities formed along phyllosilicate cleavage acted as channels for fluid transport favouring alteration under low-temperature conditions.

Water resources meet sustainability: new trends in environmental hydrogeology and groundwater engineering

Groundwater is a dynamic, finite, and vulnerable but resilient natural resource to be protected in an environmentally sustainable manner. Groundwater systems require a comprehensive understanding of climatology, geology, morphotectonics, hydrogeology, hydrogeochemistry, hydrodynamics, isotope hydrology, hydrogeomorhology, rock and soil hydrogeotechnics, and surface hydrology. Groundwater conceptual models (ground model, hydrogeological conceptual model, and numerical model)—from site investigations to regional watersheds and or global hydrological systems—based on earth systems make a major contribution to the sustainability and management of water resources. The thematic issue on “sustainability and water resources” includes a wide variety of unique contributions in environmental hydrogeology and water-related research and practice.

Urban speleology applied to groundwater and geo-engineering studies: underground topographic surveying of the ancient Arca D'Água galleries catchworks (Porto, NW Portugal)

The Porto settlement (Northwest Portugal, Iberian Peninsula) was originally built in the twelfth century and has been developed on granitic hill slopes of the Douro riverside, being one of the oldest cities in Europe. In the urban area of Porto, the second most important city of the Portuguese mainland, there is a population of about 216,000 inhabitants. This study highlights the importance of urban speleological mapping applied to groundwater and geo-engineering studies. All the water that flows from the so-called Paranhos or Arca D’Agua springs is captured by catchwork galleries and their utilization date back around 1120 AD. Paranhos spring galleries catchworks (c. 3,3 km extension and a -21m below ground level) was one of the main water supplies to Porto City for more than six centuries and, nowadays, these waters are still appropriate for irrigation uses. Topographical, geological, geophysical and hydrogeological data were collected and interpreted, allowing the definition of a hydrogeotechnical zoning. All these features were mapped and overlaid using GIS mapping techniques. This multidisciplinary approach offers a good potential for reliable urban speleological and geo-engineering studies of Arca D’Agua site.

A comprehensive analysis of groundwater resources using GIS and multicriteria tools (Caldas da Cavaca, Central Portugal): environmental issues

Hard-rock watersheds are essentially confined to fractured and weathered horizons, but they are a source of valuable water resources at a regional level, namely for domestic, industrial and agricultural purposes, and public supply. They commonly exhibit complex geological bedrock and morphological features as well as distinctive gradients in rainfall and temperature. Hydromineral and geothermal resources have relevant economic value both for the bottled water/thermal spas industry and for energy supply. A comprehensive evaluation and integrated groundwater resources study has been carried out for the Caldas da Cavaca hydromineral system in Central Portugal, using hydrogeomorphology and GIS mapping techniques. Thematic maps were organised from a geodatabase comprising several layers, namely lithology, tectonic lineaments density, slope, drainage density, rainfall, net groundwater recharge and water quality. Normalised weights were assigned to all these categories according to their relative importance to groundwater potential, based on their effectiveness factors. Hydrogeochemistry, natural radioactivity and intrinsic vulnerability assessment (GOD-S, DRASTIC-Fm, SINTACS, SI indexes) issues were also cross-checked. Based on all the compiled information, a hydrogeomorphological map was produced. This multidisciplinary approach highlights the importance of hydrogeomorphological mapping as a tool to support hydrological conceptualisation, contributing to groundwater decision-making process in different stages, like water resources management and territory planning, and thus, to environmental sustainability.

Conceptualizing a mountain hydrogeologic system by using an integrated groundwater assessment (Serra da Estrela, Central Portugal): a review

Mountains are often considered as the world’s water towers. This paper presents a critical review on the research concerning the integrated assessment of groundwater resources of the mountain hydrogeologic system of Serra da Estrela Natural Park (central Portugal). The study area is the Zêzere river basin upstream of Manteigas village located at the Serra da Estrela Mountain in Central Portugal. It provides the source of strategic water resources for the Portuguese mainland, including normal groundwaters, thermomineral waters and surface waters. An integrated approach has been used to formulate a conceptual model for this complex mountain hydrogeological system by integrating the geological, morphotectonic, hydroclimatic, unsaturated soil zone, hydrogeological, hydrogeophysical, hydrogeochemical and isotopic data. This model has been useful to: i) evaluate the water resources; ii) provide the basis for a sustainable management of water resources, iii) design measures for groundwater exploitation and contamination control; and iv) set up land-use policies.

Coupling hydrotoponymy and GIS cartography: a case study of hydrohistorical issues in urban groundwater systems, Porto, NW Portugal

The aim of this multidisciplinary study is to retrospectively examine hydrohistorical issues, namely hydrogeographic, hydrotoponymical and hydrogeological features, in order to assess the evolution of the Porto urban groundwater system (NW Portugal). To achieve these goals, the comparison of two main field inventories in a large urban region was performed by (i) historical mapping of sources and groundwater data from scientific reports spanning the late 17th century to the early 20th; and (ii) hydrogeologic and hydrotoponymical field inventory performed under current conditions. These field inventories permitted the location of springs, dug wells, fountains, public washing places and underground water galleries, which collected groundwater to supply the population of Porto until the early 20th century. This study also allowed the development of a hydrotoponymical classification for urban areas and a field hydrotoponymical inventory data sheet. This research integrated several techniques based on historical hydrogeography, hydrogeology and urban geosciences. The results of the field inventories were combined into both a database and a Geographical Information System (GIS) platform. This unified methodology allowed a cross-check and analysis of several levels of information, namely hydrotoponymy, hydroclimatology, hydrogeology, structural geology and geomorphology. This perspective led to an assessment of the evolution of the quality of water resources in large urban areas over time. In addition, the role of hydrotoponymical features is presented in order to support the hydrogeological conceptual model for large urbanised areas.

Uranyl-Evansites from Porto (Northwest Portugal) and Galicia (Northwest Spain): Structure and Assignment of Spectra Catholuminescence and Raman Bands

ABSTRACT Uranyl-evansites from Porto (Northwest Portugal) together with historical evansite standards from Galicia (Northwest Spain), Slovakia, and Congo were studied by Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive Spectrometry (EDS), Back-Scattering (BS), Spectra Cathodoluminescence (CL), Micro-Raman and X-Ray Diffraction (XRD), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This work mainly focused on Portos evansites collected from the urban underground, looking for uranyl groups and the subsequent air radon gas levels in hypogeal environments, for example, from 6000 to 7000 Bq/m3. Evansite (∼Al3(PO4)(OH)6 · 6H2O) comprises microlayers of amorphous hydrous aluminum-phosphate phases together with hydrolyzed uranyl groups and hydroxide UO2(OH)2 precipitates. The studied evansites contain uranyl groups reaching up to UO2 0.78% in the case of Kobokobo, as detected by EDS and CL, and 0.1% in the Porto samples, as detected by CL and ICP-MS. The CL spectra probe is a very fast tool in detecting uranyl groups. Raman spectra of evansites are homogeneous in samples from different localities and not previously published. Therefore, we suggest Zeleznik-type evansite as a new representative international Spectrum Raman pattern for evansite.

Scanline Sampling Techniques for Rock Engineering Surveys: Insights from Intrinsic Geologic Variability and Uncertainty

Discontinuity surveys are based on collecting rock data from fieldwork and are an essential component of rock-mass quality estimation in rock engineering. Strength, deformability and permeability characteristics of a rock-mass are strongly influenced by its discontinuities. Scanline surveys are a reliably technique in which a line is drawn over an outcropped rock surface and all the discontinuities intersecting it are measured and described. The discontinuity geometry for a rock-mass is characterised by the number of discontinuity sets, mean density and the distributions for location, orientation, size and spacing/fracture intercept. Rock site investigation deals with several key elements that need to be addressed, namely the information required to characterise the rock system and the intrinsic uncertainty associated with this information. This way, quantifying the information content of the on-site measurements and creation a database is vital to be used for decision making processes and risk assessment on rock engineering design projects. In addition, a clear geology framework plays a key-role to support the investigation of all rock engineering projects. Nevertheless, the intrinsic variability of geological, petrophysical and geotechnical properties must be quantified for reliability-based design and to decrease the geological uncertainty. All geologists and engineers’ practitioners must have the aim to contribute to the correct study of the ground behaviour of soil and rock, their applications in sustainable design with nature and environment and to satisfy the society’s needs.

Role of high mountain areas in catchment hydromineral resources - Northern/Central Portugal: environmental issues.

This study summarizes the results of geological, geomorphological, tectonic, geochemical, geophysical, hydrogeological and isotopic techniques in hydromineral resources assessment (issue temperature between 27oC and 45oC). Two case studies are presented: i) Serra da Estrela mountain region, the highest mountain in Portuguese mainland and ii) Serra do Marao mountain region. A special emphasis is dedicated to the recharge and discharge processes and the role of snowmelt as a source of hydromineral resources. Since local Spas are particularly dependent on water quality, the existence of mixing between hydromineral waters and local shallow groundwaters is also considered.