1,721,016 research outputs found
Multidisciplinary approach to provide detailed conceptual model of the aquifer systems: an example in the Versilian coastal plain (NW Tuscany)
No full textDetailed conceptual models of the aquifer systems are an essential base working for groundwater modelling and for a correct groundwater resources management. At the same time the right approach to obtain reliable conceptual models is certainly interdisciplinary, which guarantees the knowledge of geological, hydrogeological and geochemical features of the aquifer systems.
In this contribute an example of multidisciplinary study carried out on the Versilian coastal plain aquifers (NW Tuscany) is presented, underlining as the comparison between geological framework and hydraulic, hydrodynamic, chemical and isotopic data allowed at understanding the feeding mechanism of groundwater flow and at defining the seawater-freshwater mixing process.
The study area has an extension of about 55 kmq and it has delimitated by Poveromo and Motrone ditch, northward and southward respectively, and by shoreline and Apuan Alps, in the western and eastern parts. The Versilian plain constitutes a recent succession of alternating continental and marine deposits. Hydrostratigraphic cross-sections reaching a depth of about 80-100 metres were elaborated. Aquitards/aquicludes are locally interbedded to the prevalent aquifer terms, which are mainly made up by sand and gravel. Gravel is shallow in the inner portion of the plain, where the alluvial fan of Versilia River is present. Seaward gravel deepens and is overlain by sands. For this framework the aquifer results throughout a phreatic monolayer, although the local presence of superficial silty-clayey or peaty deposits may determine confined or semi-confined conditions. Moreover, the presence of a discontinuos subsurface layer of conglomerate and silty-clayley lenses may locally separate the groundwater flow in multiple levels.
In order to achieve the purpose of the present work, multiple types of hydrogeological and hydrodinamics surveys and chemical and isotopic analyses on water samples were performed. In details, two piezometric surveys and physical-chemical analyses (temperature, electrical conductivity, pH, Eh) were carried out in April 2009 (high level condition) and in September 2009 (low level condition). On the whole, 192 wells and 14 stream water points were examined.
Piezometric and iso-conductive maps suggest as the recharge area of the coastal plain is mainly the alluvial fan. Afterwards, more detailed hydrogeochemical analyses were performed. Major elements (Ca, Mg, Na, K, Cl, NO3, SO4, HCO3), some minor elements (Br, F, B, As, Fe, Mn, Pb, Cr, Cu, Ni, Zn) concentration and some isotopic ratios (2H/1H, 18O/16O for water and 13C/12C of total inorganic carbon dissolved) were estimated.
Vertical logs were also performed in order to measure the electrical conductivity and temperature into 10 wells next to the coastline. In addition, in the apex of the fan a long term pumping test was executed, determining the aquifer hydraulic parameters (K, T, S). The last, together with the potentiometric surface, allowed us estimating the groundwater flow rate at the section corresponding to the Versilia River entrance into the plain.
Finally, comparing all data, it was possible to identify the principal component which supplies the coastal aquifer system starting from the upper part of the plain, where the Versilia River feeds the groundwater hosted in its alluvial fan. Secondary contributes are linkable to the local rainfall infiltration, well recognized in the dune sand, and to the groundwater flow coming from some fractured complexes bordering the plain. Freshwater-seawater mixing processes were also individuated
Definizione delle condizioni ambientali di una discarica per rifiuti urbani e assimilabili: il caso di Literno (Isola d'Elba, Toscana)
No full textHydrogeological and geochemical features of the sandy unconfined aquifer between Marina di Pisa and Calambrone (NW Tuscany) affected by seawater intrusion
No full textA multidisciplinary approach in defining the hydrogeological model of the carbonate aquifer system in the Versilia River basin (Tuscany, Italy)
No full textA hydrogeological study was carried out on important fractured/karst aquifer systems located in the Versilia River basin (Tuscany, Italy), in order to optimize the groundwater resources management. The main aim was the individuation of the feeding areas of the most important springs by means of a multidisciplinary approach using geological, hydrogeological and geochemical-isotopic tools. Some hydrogeological sections were elaborated in order to define the geometry of the main hydrostructures and to individuate possible groundwater divides. The elaboration of geochemical data allowed at identifying 3 main chemical facies: Ca-HCO3, Ca-SO4 and Na-Cl. The first two highlight the interaction of water with limestone/dolostone and carbonate-evaporite rocks for a time sufficient to acquire these chemical compositions and to achieve saturation/supersaturation in calcite and dolomite. The Na-Cl groundwater shows low salinity and a composition similar to rainwater, indicating a circulation in rocks containing minerals not very reactive and/or short interaction time with carbonate rocks. These two main types of water-rock interaction are confirmed by the isotopic ratio δ13C: for the Ca-HCO3 and Ca-SO4 types, δ13C value requires a significant contribution of carbon derived from dissolution of calcite, while for Na-Cl water, δ13C values are consistent with the addition of biogenic CO2 in rainwater. Stable water isotopes (δ18O and δ2H) confirm that groundwaters have a meteoric origin and that the wide range of values essentially depends on the different average altitude of feeding zone. Comparing the geological and hydrogeological features with the results of the geochemical processing, it is reasonable to assume that: the Na-Cl springs are representative of the superficial circuits, with small feeding zones and very low residence times in aquifer; whereas the Ca-HCO3 and Ca-SO4 springs are representative of relatively deep circuits developed in extensive aquifers with high permeability. The first type of springs was used to obtain the relationship between the δ18O ratio and the altitude of rainwater infiltration. Taking into account that they drain a small basin and considering the regulator effect of the aquifers, the isotopic composition of these springs are very similar to the annual average isotopic values of the local meteoric water. This relationship was used to evaluate the average altitude of the feeding area of the second type of springs. All these elements, and some tracer test results available in literature, allowed us to delimit the hydrogeological basins likely drained by the most important springs under study. In addition, for each hydrogeological system, a simplified water balance using meteorological data and the effective infiltration coefficients reported in the literature was performed, verifying that the delimited catchment areas are entirely consistent with the flow rate data of the springs
Le analisi isotopiche come strumento per la valutazione dell'impatto delle discariche RSU sui corpi idrici
No full textSeveral studies carried out in Tuscany (central Italy) Municipal Solid Waste (MSW) landfills confirm that the analysis of the isotopic ratios 2H/1H, 18O/16O, 3H/H and 13C/12C is a valuable approach for the evaluation of the landfill impact on surrounding water bodies. Leachates show indeed isotopic values that strongly differ from those found in local natural waters, allowing to identify even low levels of contamination. Tritium (3H) values result to be much higher (normally between 200 and 2.000 TU) than in nowadays meteoric waters and in aquifers (commonly < 10 TU). Dissolved Inorganic Carbon (DIC) in leachate is usually characterized by δ13C (V-PDB) ‰ values between +15 and +30 δ‰, whereas natural waters have distinctly lower values (between -25 and 0 δ‰). Relationship between δ18O‰ and δ2H‰ within leachate is frequently modified too
Assessing groundwater quality and solute sources in highly anthropized areas. The case of Abuja Federal Capital Territory, Nigeria
No full textThe Abuja Federal Capital Territory is an example of a heavily anthropized aquifer, where natural water-rock interaction processes are masked by human pollution. As a result, the characterization of natural processes is particularly difficult, especially to disentangle the natural from the anthropogenic signature. Two surveys were conducted in the rainy and dry season in 2021 and 2022 using an integrated geochemical, statistical, and isotopic approach. Results show that groundwater samples are affected by mixing processes between water with a Ca-HCO3 facies (associated to natural water-rock interaction processes) and contaminated waters. The latter can be observed in some wells with a shift to NO3-dominant facies in the rainy season. The stable isotopes of the water molecule (δ18O and δ2H) suggest the presence of multiple recharge zones and strong seasonal variability. The shifts in groundwater isotopic composition suggest secondary evaporation in the rainy season and limited local precipitation influence during the dry season, with a possible domination of deep aquifer contributions. The frequency distribution of tritium (3H) in 2021 confirms the limited impact of local precipitation during the dry season (median 0.8 TU), further supporting the dominance of deep aquifer contributions to groundwater flow. The influence of rainwater infiltration is observed as a main contribution to the remobilization of contaminants (of agricultural and domestic origin) stocked in the unsaturated zone, rather than a dilution effect. This results in a progressive increase of NO3− concentration in the rainy season (reaching 433 mg/L), highlighting the need for a more complete characterization to support a wiser sustainable environmental management in an area subject to increasing anthropogenic pressure and prone to significant population growth
Progetto GEOBASI-TOSCANA, Piano Regionale di Azione Ambientale - PRAA-2009- Obiettivo E - Tutela della risorsa idrica.
No full textNel 2009 è stata approvata una convenzione tra la Regione Toscana, l’Istituto di Geoscienze e Georisorse del CNR di Pisa e le università toscane di Firenze, Pisa e Siena per la realizzazione di un progetto di ricerca e innovazione in campo territoriale e ambientale denominato “Geobasi Toscana”. Il progetto, di durata biennale, ha come obiettivo la determinazione del fondo geochimico naturale di alcune sostanze potenzialmente pericolose nonché la riorganizzazione ed elaborazione dei dati geochimici, esistenti nel panorama toscano per acque naturali (fluviali, sotterranee e di transizione) e sedimenti fluviali.
Il progetto “Geobasi Toscana” si inserisce nel percorso aperto dal progetto “Geobasi” che nel biennio 2004-2006, grazie ad un finanziamento del Ministero dell’Università e della Ricerca Scientifica, ha coinvolto diverse università italiane con il fine di affrontare la complessità del significato delle composizioni elementari di varie matrici geologiche su base multidisciplinare integrata; il progetto aveva le sue radici nelle linee guida già delineate nell’ambito di una procedente convenzione APAT-CNR che portò alla creazione dell’Archivio Geochimico Nazionale (Ottonello G. (Ed), 2008).
In questo quadro di riferimento è stato possibile procedere nell’ambito del progetto “Geobasi Toscana” alla sperimentazione di metodi innovativi per la cartografia geochimica, metodi che sono stati applicati, in via esplorativa, per lo studio del comportamento di Cd, Hg, Ni, Pb, As e Cr nei sedimenti fluviali dell’area senese e di altri parametri fra cui Cl, SO4, U e Durezza nelle acque superficiali di tutta la regione. I dati analitici utilizzati per lo studio dei sedimenti fluviali riguardano 417 campioni di prelevati nella provincia di Siena. Il campionamento è stato effettuato su una superficie complessiva di circa 2000 km2 con una densità di 1 campione ogni 5 km2. I dati analitici relativi ai campioni di acque (949 campioni) provengono da campionature del CNEN degli anni ’60 e sono stati elaborati attraverso vari strumenti di calcolo, di tipo sia deterministico che geostatistico.
In particolare, sono stati applicati metodi di analisi spaziale adatti per lo studio dei dati composizionali, dati cioè caratterizzati dal fatto che ogni variabile rappresenta una proporzione di un totale prefissato a priori (percentuali, parti per milione, frazioni molari, etc.). Questo tipo di dati dal punto di vista geometrico non occupa uno spazio reale, le cui dimensioni sono pari al numero delle variabili, ma sono collocati in uno spazio ristretto, contenuto nello spazio reale, noto con il nome di simplesso (Aitchison, 1986). Questa situazione di geometria vincolata, non euclidea, crea non pochi problemi quando per l’analisi dei dati sono utilizzati i metodi della statistica classica. In questo lavoro di ricerca sono pertanto proposti e presentati nuovi metodi grafici e numerici alternativi rispettosi delle peculiarità geometriche dello spazio campionario in cui i dati mostrano le loro caratteristiche. I risultati sono discussi alla luce del comportamento geochimico degli elementi sopra indicati in relazione con i lineamenti geolitologici dell’area investigata
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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