Maria José Afonso

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.

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.

Recovery of Ancient Groundwater Supply Systems and Old Abandoned Mines: Coupling Engineering Geosciences and Geoheritage Management

This work aims to highlight the coupling of engineering geosciences and geoheritage studies on an integrative multidisciplinary approach to the recovery processes of abandoned mining heritage. In order to fulfil these goals an experimental site was selected in S. Martinho de Tibaes Monastery enclosure. Some abandoned water mines were part of an impressive water supply system of the monastery between 17th and 19th centuries. The Aveleiras Mine site was also exploited in the first half of the 20th century as a wolfram mine for over 23 years. Specific actions were developed to rehabilitate some sites, in order to facilitate their inclusion in selected hydrogeo-itineraries to the wide public. This will demonstrate their early purpose, i.e., to provide water to the gardens and orchards of the monastery. In addition, the recovery of abandoned mining sites is a worthy example of an organization transformative process towards a second life-cycle in geotourism, natural heritage and cultural assets. Such interventions represent important measures for sustainability and the surrounding environment.

Geomechanical Assessment on a Metasedimentary Rock Cut Slope (Trofa, NW Portugal): Geotechnical Stability Analysis

This work emphasises the importance of a detailed geomechanical study to a better geotechnical understanding of a weak rock mass. In addition, Geographic Information Systems (GIS) tools for spatial analysis and rock database overlay were applied. The stability of a metasedimentary rock cut slope in Trofa region (NW Portugal, Iberian Peninsula) was studied. The main geomorphological, geological, geotechnical and geomechanical constraints were characterised and integrated along a highly deformed phyllitic rock mass. The scanline sampling technique of discontinuities has been applied to the study of basic geotechnical description of free rock mass surfaces. In order to classify the quality of the phyllitic rock mass, basic Rock Mass Rating (RMR), Slope Mass Rating (SMR) and the Geological Strength Index (GSI) were applied. The structural and geotechnical solution for the stabilisation of the cut slope was outlined. This methodology turned out to be valuable to understand the behaviour of slope stability in weak rock mass and it can be useful to the accurate estimation of future unstable rock slope.

Enigmatic reticulated filaments in subsurface granite: 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.