1,721,016 research outputs found
A synthesis of the Antarctic surface mass balance during the last 800 yr
No full textGlobal climate models suggest that Antarctic snowfall should increase in a warming climate and mitigate rises in the sea level. Several processes affect surface mass balance (SMB), introducing large uncertainties in past, present and future ice sheet mass balance. To provide an extended perspective on the past SMB of Antarctica, we used 67 firn/ice core records to reconstruct the temporal variability in the SMB over the past 800 yr and, in greater detail, over the last 200 yr. Our SMB reconstructions indicate that the SMB changes over most of Antarctica are statistically negligible and that the current SMB is not exceptionally high compared to the last 800 yr. High-accumulation periods have occurred in the past, specifically during the 1370s and 1610s. However, a clear increase in accumulation of more than 10% has occurred in high SMB coastal regions and over the highest part of the East Antarctic ice divide since the 1960s. To explain the differences in behaviour between the coastal/ice divide sites and the rest of Antarctica, we suggest that a higher frequency of blocking anticyclones increases the precipitation at coastal sites, leading to the advection of moist air in the highest areas, whereas blowing snow and/or erosion have significant negative impacts on the SMB at windy sites. Eight hundred years of stacked records of the SMB mimic the total solar irradiance during the 13th and 18th centuries. The link between those two variables is probably indirect and linked to a teleconnection in atmospheric circulation that forces complex feedback between the tropical Pacific and Antarctica via the generation and propagation of a large-scale atmospheric wave train. © 2013 Author(s)
Realizzazione dei piezometri nel campo geotermico sperimentale del C.R. ENEA-Casaccia e misure di conducibilità tecnica
Full text linkL’attività descritta in questo report è parte del progetto di ricerca, relativo al Piano Triennale di realizzazione 2022-2024 della Ricerca di Sistema Elettrico Nazionale, linea di attività 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Nello specifico, l’attività in oggetto è la L.A. 4.1 (WP4). Nel primo anno e mezzo di attività sono stati realizzati due fori attrezzati a piezometri, per monitorare temperatura e livello dell’acqua di falda nel campo geotermico realizzato nel 2021, costituito da 4 pozzi a diversa profondità (da 35 a 85 m), a circuito chiuso e con configurazione a doppia U (cfr. RT/2023/23/ENEA). Le due perforazioni (PZ1 e PZ2), profonde 45 m, sono state eseguite a carotaggio continuo nel marzo 2023. Di ogni litotipo è stato estrapolato il valore del coefficiente di permeabilità e di porosità efficace. È stata determinata la portata unitaria attraverso i diversi strati, tenuto conto della permeabilità del litotipo e del gradiente idraulico effettivamente calcolato. Inoltre, sono state caratterizzate le litologie attraversate in ogni foro ed è stata effettuata la correlazione litostratigrafica tra i due siti. Misurazioni dirette di conducibilità termica sono state eseguite, all’atto del recupero, sulle carote dei sondaggi PZ1 e PZ2, in condizioni sostanzialmente indisturbate. I valori sono stati confrontati con le misure effettuate in laboratorio sulle carote del sondaggio geognostico S1 (corrispondente al pozzo 1 del campo geotermico) correlando le successioni litostratigrafiche fino alla profondità di 45 m. Da 45 a 85 m sono stati considerati i valori di conducibilità termica media misurati in laboratorio sui campioni del sondaggio S1. Su tutti i campioni dei sondaggi S1, PZ1 e PZ2 sono stati calcolati densità e calore specifico, con l’intento di utilizzare tali valori nelle future fasi di modellizzazione termica del campo geosonde. I dati rilevati ogni 12 ore dai piezometri hanno permesso di definire la quota del livello statico della falda acquifera e di registrarne le variazioni in funzione della pluviometria.The activity described in this report is part of the research project, related to the 2022-2024 ThreeYear Implementation Plan of the National Electricity System Research, activity line 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Specifically, this activity is L.A. 4.1 (WP4). In the first year and a half of activity, two boreholes equipped with piezometers were drilled, to monitor temperature and groundwater level in the geothermal field constructed in 2021 and consisting of 4 boreholes at different depths (from 35 to 85 m), with a closed circuit and a double U configuration (see RT/2023/23/ENEA). The two 45 m deep boreholes (PZ1 and PZ2) were drilled by continuous coring in March 2023. The value of the permeability coefficient and effective porosity was extrapolated for each lithotype. The unit flow rate through the different layers was determined, considering the permeability of the lithotype and the effectively calculated hydraulic gradient. In addition, the lithologies crossed in each borehole were characterised and the lithostratigraphic correlation between the two sites was carried out. Direct measurements of thermal conductivity were carried out, upon recovery, on the cores of boreholes PZ1 and PZ2 under substantially undisturbed conditions. The values were compared with laboratory measurements on the cores of geognostic survey S1 (corresponding to borehole 1 of the geothermal field) by correlating the lithostratigraphic successions up to a depth of 45 m. From 45 to 85 m, the mean thermal conductivity values measured in the laboratory on the S1 samples were considered. Density and specific heat were calculated on all samples from S1, PZ1 and PZ2, to use these values in future thermal modelling of the geosonde field. The data collected every 12 hours from the piezometers made it possible to define the static level of the aquifer and to record its variations as a function of the rainfall
Ice record of a 13th century explosive volcanic eruption in northern Victoria Land, East Antarctica
No full textA volcanic event, represented by both coarse ash and a prominent sulphate peak, has been detected at a depth of 85.82 m in a 90 m ice core drilled at Talos Dome, northern Victoria Land. Accurate dating of the core, based on counting annual sulphate and nitrate fluctuations and on comparison with records of major known volcanic eruptions, indicates that the event occurred in 1254 ± 2 AD. The source volcano is most likely to be located within the Ross Sea region. In particular, the glass shards have a trachytic composition similar to rocks from The Pleiades and Mount Rittmann (Melbourne volcanic province), about 200 km from Talos Dome. Sulphate concentration is comparable with that of violent extra-Antarctic explosive events recorded in the same core, but atmospheric perturbation was short-lived and localized, suggesting a negligible impact on regional climate. It is suggested that this eruption may represent the most important volcanic explosion in the Melbourne province during the last eight centuries; thus this event may also represent a valuable chrono-stratigraphical marker on the East Antarctic plateau and in adjoining areas
Understanding uranium behaviour in a natural rock–water system: leaching and adsorption tests on the Tufo Rosso a Scorie Nere ignimbrite (Viterbo area, central Italy)
No full textBased on both chemical leaching and adsorption tests and a simple modelling using PHREEQC, geochemical behaviours of uranium during the ignimbrite–water interaction were evaluated mainly as a function of temperature, pH, and solution chemistry (esp., alkalinity). The main results of this work are: (1) uranium is more easily mobilized by slightly basic solution (pH 7.5) than by acidified water (pH 4.5) when relative concentrations of the main uranyl ion–calcium–carbonate species, Ca2UO2(CO3)3, increase from 0.6 to 90%; (2) the greatest leaching of uranium occurs at 50 °C (not at higher temperature) because the first dissociation constant of H2CO3 is directly correlated with temperature up to about 50 °C, but decreases from 50 to 80 °C. This directly influences the concentration of HCO3 − which is mirrored by dissolved CO2 variations; (3) the presence of alkalinity, total C-species and calcium controls the saturation index of sorbate solution with respect to calcite, influencing also speciation, solubility, and sorption of dissolved U; and (4) higher adsorption of uranium is obtained in tests with deionized water (90.0 ± 0.7 mg/kg, at equilibrium) compared to those performed with the natural water (26.0 ± 1.5 mg/kg, at equilibrium), strengthening the role of complexes between uranyl, HCO3 −, and Ca2+ ions in solution to explain the corresponding decrease in uranium adsorption. © 2017, Springer-Verlag GmbH Germany
A database of the coseismic effects following the 30 October 2016 Norcia earthquake in Central Italy
No full textWe provide a database of the coseismic geological surface effects following the Mw 6.5 Norcia earthquake that hit central Italy on 30 October 2016. This was one of the strongest seismic events to occur in Europe in the past thirty years, causing complex surface ruptures over an area of >400 km 2. The database originated from the collaboration of several European teams (Open EMERGEO Working Group; about 130 researchers) coordinated by the Istituto Nazionale di Geofisica e Vulcanologia. The observations were collected by performing detailed field surveys in the epicentral region in order to describe the geometry and kinematics of surface faulting, and subsequently of landslides and other secondary coseismic effects. The resulting database consists of homogeneous georeferenced records identifying 7323 observation points, each of which contains 18 numeric and string fields of relevant information. This database will impact future earthquake studies focused on modelling of the seismic processes in active extensional settings, updating probabilistic estimates of slip distribution, and assessing the hazard of surface faulting. © 2018 The Author(s)
Impianto geotermico sperimentale a bassa entalpia presso il C.R. ENEA-Casaccia. Caratterizzazione termica stagionale, assemblaggio del circuito di prova, risultati del monitoraggio
Full text linkL’attività descritta nel presente report è parte del progetto di ricerca, relativo al Piano Triennale di realizzazione 2019-2021 della Ricerca di Sistema Elettrico Nazionale, linea di attività 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Nello specifico, l’attività in oggetto è la L.A. 3.24, contenuta nel WP3. Nel terzo anno, l’attività è stata incentrata sullo studio e la caratterizzazione termica stagionale del campo geosonde. Per la difficoltà a reperire alcune componenti dell’impianto, causata dalla situazione pandemica, l’assemblaggio del circuito di prova ha subìto ritardi, e quindi il monitoraggio dei valori termometrici all’interno dei pozzi è stato effettuato a circuito spento. Tutti i dati mensili di temperatura dei quattro pozzi sono stati confrontati con i dati del mese di maggio del pozzo 1, in quanto risente ancora delle variazioni di temperatura indotte durante il test di risposta termica (GRT) effettuato il 15 aprile 2021. Sulla base dei dati di temperatura è stato possibile estrapolare la curva di conducibilità termica sperimentale della successione stratigrafica. Inoltre, con l’utilizzo della simulazione termica computazionale si è ricostruita l’alterazione del campo termico indisturbato del terreno sotto l’azione del geoscambio sonde-terreno. Successivamente, il confronto tra i dati climatici annuali registrati dalle stazioni meteorologiche all’interno del C.R. Casaccia con le temperature rilevate direttamente dalle fibre ottiche ha consentito di determinare la profondità fin dove si risente dell’irraggiamento solare nei quattro pozzi. Sono stati calcolati i valori di resistenza termica equivalente dello scambiatore a terreno, ed è stato descritto il funzionamento dell’impianto, le sue componenti, gli strumenti di controllo e di monitoraggio.The activity described in this report is part of the research project, related to the 2019-2021 ThreeYear Implementation Plan of the National Electricity System Research, activity line 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Specifically, this activity is L.A. 3.24, contained in WP3. In the third year, the activity focused on the study and seasonal thermal characterisation of the geosonde field. Due to the difficulty in finding part of the plant components, caused by the pandemic situation, the assembly of the test circuit was delayed and therefore the monitoring of the thermometric values inside the wells was carried out while the circuit was switched off. All monthly temperature data of the four wells were compared with the May data of well 1, as it was still affected by the temperature variations induced during the thermal response test (GRT) carried out on 15 April 2021. Based on the temperature data, it was possible to extrapolate the experimental thermal conductivity curve of the stratigraphic succession. In addition, with the use of computational thermal simulation, the alteration of the undisturbed thermal field of the ground under the action of probe-soil geo-exchange was reconstructed. Subsequently, the comparison of the annual climatic data recorded by the meteorological stations in the C.R. Casaccia with the temperatures measured directly by the optical fibres made it possible to determine the depth to which solar radiation is detected in the four wells. The equivalent thermal resistance values of the ground heat exchanger were calculated, and the functioning of the plant, its components, control, and monitoring instruments were also described
Comparative life cycle assessment of the ground source heat pump vs air source heat pump
No full textIn view of the decarbonisation of the thermal sector, the use of ground source heat pumps (GSHP) plays a key role. The geothermal system coupled with heat pumps, is the most energy efficient and environmentally sustainable heating and cooling system because the ground temperature is constant all year round, unlike traditional air-source heat pumps (ASHP). A comparative life cycle assessment of a pilot GSHP system, operating in the ENEA Casaccia Research Centre (Italy), and a conventional ASHP was performed. In accordance with ISO standard, the impacts on the four damage criteria were evaluated for each phase of the entire life cycle (production, installation, operation and end-of-life), using the SimaPro 9.0 software. The GSHP system has significant impacts compared to the other ASHP system components during manufacturing and installation. In contrast, slightly higher impacts of the ASHP system are recorded during the operational phase. It should be considered that the geothermal probe circuit has a useful life of 100 years, which allows for multiple operational life cycles of the geothermal plant. Therefore, the paper highlights that the GSHP system, as a whole, is more energy efficient and has a lower long-term environmental impact, compared to a traditional air conditioning system
Volcanic Records at GPS1, GPS2, 31DPT and M2 Stations along the 1998-99 ITASE Traverse (East Antarctica).
No full textStudio preliminare di fattibilità e dimensionamento di massima di un impianto geotermico sperimentale a bassa entalpia integrato con pompa di calore
No full textQuesto Rapporto descrive le attività svolte durante la prima annualità del Piano Triennale di realizzazione 2019-2021 della Ricerca di Sistema Elettrico Nazionale, riguardanti la linea di attività 1.7 denominata “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. Lo studio in oggetto è stato anzitutto indirizzato alla ricostruzione dell’assetto litologico-stratigrafico e idrogeologico dell’area del C.R. ENEA-Casaccia, attraverso il reperimento sistematico e la consultazione di tutti i dati di letteratura disponibili e delle stratigrafie dei sondaggi geognostici effettuati nel C.R. Casaccia. La valutazione geologica ha permesso inoltre di estrapolare il valore di conducibilità termica delle rocce presenti nell’area e di individuare il sito in cui insisterà il sistema di approvvigionamento del calore dal terreno, utilizzando sonde geotermiche verticali accoppiate a una pompa di calore (PdC) acqua-acqua. Successivamente, è stata condotta una simulazione dei carichi termici assumendo come target, per la sorgente terreno, la climatizzazione di un ufficio (con superficie di 140 m2 circa, situato nell’edificio F40 del C.R. Casaccia, adiacente al campo geosonde). Tramite un software dedicato è stato possibile dimensionare le sonde inserendo i valori dei carichi di picco invernali ed estivi. Si prevede di realizzare 4 pozzi, profondi rispettivamente 35 m, 50 m, 80 m e 100 m. Il campo geosonde sarà dotato di un sistema di controllo mediante fibre ottiche impiantate direttamente all’interno dei tubi in polietilene, al fine di monitorare costantemente i valori termometrici all’interno di ogni pozzo e quindi definire il campo termico, la sua evoluzione nell’arco delle stagioni, e non ultimo l’efficienza del sistema sonde-terreno nel tempo. Infine, è stato stimato il valore della potenza termica estratta durante l’inverno e stoccata in estate, il consumo energetico della pompa di calore e le emissioni di CO2 e NOX.This Report deals with the activities carried out during the first year of the 2019-2021 Three-Year Implementation Plan for National Electricity System Research, concerning line 1.7 “Tecnologie per la penetrazione efficiente del vettore elettrico negli usi finali”. First, this study was aimed at reconstructing the lithological-stratigraphic and hydrogeological structure of the area of the ENEA-Casaccia Research Centre, through the systematic retrieval and consultation of all the available literature data and the stratigraphies of the geognostic drillings carried out at the C.R. Casaccia. The geological assessment also allowed the extrapolation of the thermal conductivity value of the rocks in the area and to identify the site where the ground heat supply system will be installed, using vertical geothermal probes coupled with a water-water heat pump (HP). Subsequently, a simulation of thermal loads was conducted, assuming as the target, for the ground source, the air conditioning of an office (with a surface area of approximately 140 m2, located in building F40 of C.R. Casaccia, adjacent to the geothermal probe field). Using dedicated software, it was possible to size the probes by entering the winter and summer peak load values. Four boreholes are planned: 35 m, 50 m, 80 m and 100 m deep, respectively. The geothermal probe field will be equipped with a control system using optical fibres implanted directly inside the polyethylene pipes, to constantly monitor the thermometric values inside each well and thus define the thermal field, its evolution over the seasons, and not least the efficiency of the probe-soil system over time. Finally, the value of the thermal power extracted in winter and stored in summer, the energy consumption of the HP and CO2 and NOX emissions were estimated
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