1,720,964 research outputs found
Hydrogeophysical Methods for Water Resources Protection and Management
No full textIn this chapter we present a brief description of hydrogeophysical methods and their history over the past twenty years, with specific reference to their application for water resources protection and management. This generally requires that geophysical methods, and electrical/electromagnetic methods in particular, are used in time-lapse mode, thus allowing us to monitor hydrological changes in the subsurface. These data, in turn, can be used for calibration of hydrological models or for a better conceptualization of the subsurface hydrological processes. This can be done at a large variety of scales, even though here we present cases relevant to the small to intermediate scale. Examples concerning soil, vadose zone, hillslope and hydrogeological processes are shown and discussed
Combined GPR and seismic refraction tomography to study the subsoil in the Cathedral of S. Giorgio Ragusa- Ibla (Sicily)
No full textIn this work, we show GPR surveys combined with a series of seismic refraction tomographies to study the subsoil in the Cathedral of S. Giorgio in Ragusa Ibla (Sicily). The church stands on a high structural level characterized by a carbonate formation, consisting of a calcarenite-marly succession. Built in the 18th century, where previously stood the church of San Nicola, the new building probably hosts, under the present flooring, several tombs of different ages and probable remains of the oldest previous church. The combination of the two geophysical methods here proposed allows us to highlight the potential of each technique and how they perfectly support the reconstruction of the subsoil of the church with different details on archaeological and geological/structural buried structures
Snowmelt and subsurface heterogeneity control tree water sources in a subalpine forest
Full text linkIn high mountain areas, snowmelt water is a key-yet fading-hydrological resource, but its importance for soil recharge and tree root water uptake is understudied. In these environments, heterogeneous terrains enhance a highly variable availability of soil and groundwater resources that can be accessed by plants. We conducted a tracer-based study on a subalpine forest in the Italian Alps. We investigated the isotopic composition (2H and 18O) of snowmelt, precipitation, spring water, soil water-at different locations and depths-and xylem water of twigs taken from alpine larch, Swiss stone pine and alpenrose plants during bi-weekly field campaigns (growing seasons of 2020 and 2021). Mixing models based on delta 18O revealed a large contribution of snowmelt to soil and xylem water, particularly during early summer. We investigated the contribution of water from different soil depths to xylem water, using the sap flow records to date back the end-member signatures. We found a flexible use of shallow and deeper soil water by the investigated plants, with groundwater more likely used by larger trees and during the late summer. Results based on isotopic data were combined with geophysical observations of the subsurface structure to develop a conceptual model about the different exploitation of water by plants depending on their location (shallow soil on a slope vs. a saturated area). Our study highlights the relevance of snowmelt in high-elevation terrestrial ecosystems, where heterogeneous substrates shape the water availability at different depths and, in turn, water uptake by plants
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
Comparison of multi-coil and multi-frequency frequency domain electromagnetic induction instruments
Full text linkIntroductionCharacterization of the shallow subsurface in mountain catchments is important for understanding hydrological processes and soil formation. The depth to the soil/bedrock interface (e.g., the upper ~5 m) is of particular interest. Frequency domain electromagnetic induction (FDEM) methods are well suited for high productivity characterization for this target as they have short acquisition times and do not require direct coupling with the ground. Although traditionally used for revealing lateral electrical conductivity (EC) patterns, e.g., to produce maps of salinity or water content, FDEM inversion is increasingly used to produce depth-specific models of EC. These quantitative models can be used to inform several depth-specific properties relevant to hydrological modeling (e.g. depths to interfaces and soil water content).Material and methodsThere are a number of commercial FDEM instruments available; this work compares a multi-coil device (i.e., a single-frequency device with multiple receiver coils) and a multi-frequency device (i.e., a single receiver device with multiple frequencies) using the open-source software EMagPy. Firstly, the performance of both devices is assessed using synthetic modeling. Secondly, the analysis is applied to field data from an alpine catchment.ResultsBoth instruments retrieved a similar EC model in the synthetic and field cases. However, the multi-frequency instrument displayed shallower sensitivity patterns when operated above electrically conductive grounds (i.e., 150 mS/m) and therefore had a lower depth of investigation. From synthetic modeling, it also appears that the model convergence for the multi-frequency instrument is more sensitive to noise than the multi-coil instrument.ConclusionDespite these limitations, the multi-frequency instrument is smaller and more portable; consequently, it is easier to deploy in mountainous catchments
Utilizzo di tecniche di prospezione geoelettrica per lo studio dell'interazione suolo-radici
Full text linkIn this study we aimed to use the technique of geoeletrical prospection ERT, to investigate the interaction between the soil and the root system of an Olive tree sited in Tuscany.
The data have been elaborated through various softwares like Prosys II, Paraview and MatLab.
The results obtained show how this approach can give us information related to the location of the roots in the soil, and trace the diffusion of the wet volume in a time-lapse sequenceope
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Electromagnetic methods for near-surface applications: a critical analysis of different investigation approaches
Full text linkCollecting the information regarding the sedimentary patterns of ancient tidal channels and providing a better understanding of their influence on the morphodynamic evolution of the lagoon environment, requires an expensive process that involves high resolution sediment coding. In this work we discuss the methods and results obtained from the electromagnetic survey carried out in the northern Venice Lagoon. We investigated meander deposit using two different conductivity meters: a multi-coil sensor and a multifrequency one.
The aim of this study was to reveal the lateral and vertical structure of the meander body.
The interpretation of the geophysical data has been correlated with borehole analysis, carried out from five sediment cores collected on the site area. In addition, the information regarding the architectural structure of the point bar deposit observed in the channel, from two seismic profile shown in the literature, has been considered.
The results show that this method allows us to identify a sand deposit buried in a mud-silty contest, that is not related with the point bar deposit identified with the tidal meander.
Moreover, we demonstrated that the proposed geophysical technique, is not only rapid and non-invasive, but is also a successful tool in detecting strata architecture and the definition of its spatial distribution
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