• Energy Research

Geothermal energy is a form of renewable energy with a long tradition in European countries, although it is scarcely used in Spain. One of the reasons for this is the poorly studied geothermal potential of the Spanish territory. In recent years, data published on terrestrial gamma radiation and the geochemistry of radioisotopes in rocks have suggested that the radiogenic heat production (RHP) in some areas of Spain is high. In this work, we assessed the RHP by analysing the U, Th, and K contents of the rocks underlying the most important campus of the University of A Coruña (northwest Spain), using in situ handheld gamma-ray spectrometry (GRS) and X-ray fluorescence spectrometry (XRF). Our results provide a good fit of the radioisotope contents and unexpectedly high RHP, compared with average data observed in similar rocks (granodiorite). These results reveal that GRS is a very reliable tool for studying the RHP of rock surfaces, and that geothermal energy can be used in the area (i.e., the studied campus, but also most of the city of A Coruña, as it is built on the same underlying rock) for central heating in buildings using ground-source heat pumps (GSHPs).

Materials in the built environment are exposed to several agents that promote alteration processes resulting in features that might be considered detrimental of its value. There are diverse possible intervention measures that might, however, have unwanted side effects. Here are reviewed the main issues related to the struggle against these alteration processes, from the consideration of the intervention criteria to strategic considerations on the organisation of the intervention that must include temporal and spatial features of alteration processes, as well as possible interventions on the surroundings of the materials and in the materials, including its replacement. The long-term effectiveness of these interventions is linked with the global strategy namely in relation to the conditions that promote alteration processes. Some sustainability questions related to the intervention operations are also considered such as the use of toxic substances and the consumption of resources.

El flujo de calor en la corteza superior determina la posibilidad de utilizar la energía geotérmica en una determinada zona. Este flujo es muy heterogéneo por lo que el aprovechamiento de la energía geotérmica es muy variable y requiere un estudio de cada zona. Donde no existen condicionantes geológicos que produzcan un flujo de calor anómalo y elevado, el aprovechamiento de esta energía es más limitado, dependiendo de las propiedades de las rocas del substrato, pero aun así enormemente variable. Los estudios realizados en Galicia hasta la fecha indican que el aprovechamiento geotérmico en esta comunidad es limitado debido a la ausencia de anomalías y a la litología, existiendo un potencial geotérmico bajo. Sin embargo, los principales estudios orientados a este fin, aun considerando información geológica, han sido genéricos, imprecisos y conservadores. La existencia de nuevos datos geoquímicos y de radiación gamma permite una reevaluación de estos estudios. Esta reevaluación muestra un potencial mayor del estimado inicialmente, lo que sugiere la necesidad de realizar estudios más detallados de la geoquímica de las rocas para obtener una evaluación más precisa y exacta, algo necesario para un desarrollo adecuado del aprovechamiento de esta energía en la comunidad.

[Abstract] Water has always been a critical resource for humans and climate change could aggravate supply problems. In this context, groundwater could be an important reservoir of water, especially given the dispersion of places where it can be obtained and the widespread occurrence of surface marks (springs). Historically, places where groundwater is available have been marked by humans using built structures, with stone materials having a major role. These cultural objects tend to become a part of the collective memory and the historical record (when available) and frequently they stay on the original site along time (hence “marking a spot” for groundwater). However, the development of major water supply structures, especially in the 20th century, promoted the negligence of these ancient water sources. We present a general defense of the importance of recording and preserving cultural stone related to water sources, preferably in the original sites. Conservation of groundwater-related structures could help in the future exploration of this geological resource and converge with historical information on the fountains’ discharge, with geological studies of the terrains and geochemical features of the groundwaters involved, in order to characterize the hydrogeological systems and their potential future use (including the preservation of water quality and properties). These studies could promote a synergetic conservation of both heritage and water. Portugal. Fundação para a Ciência e a Tecnologia; UIDB/04509/2020 Portugal. Fundação para a Ciência e a Tecnologia; UIDB/04028/2020 Xunta de Galicia; ED431B 2018/47 Xunta de Galicia; R2017/008 The Lab2PT-Landscapes, Heritage and Territory laboratory—UIDB/04509/2020 is supported by the Portuguese FCT—“Fundação para a Ciência e a Tecnologia”. The authors also gratefully acknowledge the support of the CERENA (funded by a strategic project of the FCT UIDB/04028/2020) and the LAMPIST of the DECivil, Instituto Superior Técnico, University of Lisbon, Portugal. The University Institute of Geology of the University of A Coruña (Spain) receives support from the Xunta de Galicia from the program “Consolidación y estructuración de unidades de investigación competitivas: Grupos de potencial de crecimiento” (ED431B 2018/47) and Redes de investigación (R2017/008). We also thank the IACOBUS Program from the European Strategic Group of Territorial Cooperation Galicia/North of Portugal for support for the last author The Lab2PT-Landscapes, Heritage and Territory laboratory—UIDB/04509/2020 is supported by the Portuguese FCT—“Fundação para a Ciência e a Tecnologia”. The authors also gratefully acknowledge the support of the CERENA (funded by a strategic project of the FCT UIDB/04028/2020) and the LAMPIST of the DECivil, Instituto Superior Técnico, University of Lisbon, Portugal. The University Institute of Geology of the University of A Coruña (Spain) receives support from the Xunta de Galicia from the program “Consolidación y estructuración de unidades de investigación competitivas: Grupos de potencial de crecimiento” (ED431B 2018/47) and Redes de investigación (R2017/008). We also thank the IACOBUS Program from the European Strategic Group of Territorial Cooperation Galicia/North of Portugal for support for the last author

[Abstract] In an effort to understand how alpine environments from the western Mediterranean region responded to climate variations since the last glacial-interglacial transition, a detailed chronological control and sedimentological analysis, supported by magnetic susceptibility, total organic carbon and C/N data, were carried out on the sedimentary record of Laguna Seca (LS). This is a latitudinal and altitudinally (2259 masl) key alpine wetland site located in the easternmost area of the Sierra Nevada, southern Iberian Peninsula, where sediments accumulated during Heinrich Stadial 1, Bølling-Allerød (B-A) and the Younger Dryas (YD) - previously unrecorded in alpine Sierra Nevada. Climate controlled sedimentation in LS and three coarse-grained and one fine-grained facies association are differentiated, which help us decipher the paleoenvironmental evolution of LS: (1) subaerial cohesionless debris flows during a paraglacial stage; (2) till or nival diamicton during a small glacier/nivation hollow stage; (3) massive mudstone by suspension settling of clays into standing water during a lacustrine stage; and (4) frost-shattering breccia deposited inside the lacustrine stage, probably during the YD, and linked to a periglacial substage. The development of a previously existing small glacial cirque during the Last Glacial Maximum (LGM) in the LS basin at an elevation between 2500 and 2300 m could be supported by the important availability of slope sediments glacially-conditioned such as debris flows, reworked by paraglacial slope processes during the first deglaciation stages, confirming previous studies of landforms in the catchment area and the LGM-Equilibrium Line Altitude estimation above 2400 masl in Sierra Nevada. Mean sediment accumulation rates in the LS sedimentary units (4.21 and 0.28 mm/yr during the paraglacial - small glacier/nivation stage and the lacustrine stage, respectively) confirm that geomorphic activity accelerated just after glaciers retreated due to a slope adjustment and high availability of glacially conditioned sediments. An abrupt change in paleoenvironmental and paleoclimatic conditions occurred in LS at ∼ 15.7 cal kyr BP. This change was probably due to an increase in temperature and precipitation in the western Mediterranean region during the B-A. At LS, this resulted in significant ice-melt, forming a deep-water lake in LS with important organic matter contribution until the end of the Early Holocene (except in the YD when the lake level probably dropped), but elsewhere a general glacier recession in the Sierra Nevada and an expansion of the Mediterranean forest in the southern Iberian Peninsula. Finally, the general long-term aridification that occurred during the Middle Holocene until the present in the western Mediterranean region triggered an important environmental change transforming LS into an ephemeral wetland with an increase in aquatic productivity. This study is was supported by the I + D + i projects CGL2013-47038-R and CGL2017-85415-R funded by Ministerio Ciencia e Innovación/Agencia Estatal de Investigación/ 10.13039/501100011033/ and Fondo Europeo de Desarrollo Regional “Una manera de hacer Europa”, I + D + i projects B-RNM-144-UGR18 and P20_00059 of the action “Proyectos I + D + i del Programa Operativo FEDER - Junta de Andalucía - UGR” and the research group RNM-190. Alejandro López Avilés acknowledges the predoctoral fellowship BES-2018-084293 provide by the MCIN/ AEI/ 10.13039/501100011033/. Antonio García-Alix acknowledges the Ramón y Cajal fellowship RYC-2015-18966 provided by the MCIN/ AEI/ 10.13039/501100011033/. Fernando García García collaboration in this study was supported by the I + D + I project CGL2017-89618-R funded by MCIN/ AEI/ 10.13039/501100011033/ and FEDER “Una manera de hacer Europa” and the research group RNM-178. José Carrión collaboration in this study was supported by the I + D + I project PID2019-1049449 GB-I00 funded by MCIN/ AEI/ 10.13039/501100011033/ and FEDER “Una manera de hacer Europa” and the fellowship 20788/PI/18 of Fundación Séneca Junta de Andalucía; B-RNM-144-UGR18 Junta de Andalucía; P20_00059 Fundación Séneca; 20788/PI/18

Materials on the built environment are exposed to several agents that promote alteration processes resulting in features that might be considered detrimental of its value. Here we review the main issues related to the struggle against these alteration processes, from the consideration of the intervention criteria, including the non-intervention option, to strategic considerations on the organisation of the intervention that must consider the temporal and spatial features of the alteration processes, as well as possible interventions on the surroundings of the materials, e.g. atmosphere, terrain and structure, and in relation to treatments of materials, including its replacement. It is highlighted the problem of testing using small clean specimens aggravated by comparative studies based on one specimen by case. Assessment of short-term an effects is discussed in relation to intrinsic aspects of the interventions. The long-term effectiveness is linked with the global strategy namely in relation to the conditions that promote the alteration processes. Some sustainability questions related to the intervention operations are also considered such the use of toxic substances and the consumption of resources The Centre of Geological Research, Management and Valorisation of Resources (CIG-R) is supported by the Fundação para a Ciência e Tecnologia (Portugal) Portuguese funds (PEst-OE/CTE/UI0697/2011). The collaboration between the authors in this subjected has benefited from Portuguese-Spanish collaboration Project “Ação Integrada E-141/10” (Fundação das Universidades Portuguesas)/“Acción Integrada PT2009-0077” (Ministerio de Ciencia e Innovación). info:eu-repo/semantics/publishedVersion Postprint: versão dos autores