1,721,003 research outputs found
Protection from natural and anthropogenic sources: a new rating methodology to delineate "Nitrate Vulnerable Zones"
No full textIn the last years, because of uncontrolled human activities, a significant increase of groundwater pollution occurred worldwide, with nitrate being among the most widespread pollutants. The assessment of groundwater vulnerability represents an important tool for developing groundwater quality plans and in the delimitation of Nitrate Vulnerable Zones. In this study, three rating methods (DRASTIC, SINTACS and GOD) were applied in an alluvial plain to check the reliability of the results comparing the obtained thematic maps with the observed nitrate concentrations in groundwater. Results show that without large modifications for specific vulnerability, these methodologies cannot describe the actual groundwater nitrate distribution in the study area. A new easy methodology called Protection from Natural and Anthropogenic sources (PNA) was then defined and tested. The PNA map divides the study area in five classes of vulnerability from very low to very high and shows a fair correlation with groundwater nitrate concentrations. The selection of the parameters and of the algorithm makes PNA strongly flexible and applicable in similar watersheds around the world, as a tool for the delineation of Nitrate Vulnerable Zones
Rainstorm-induced soil 222Rn concentration spikes observed in Southern Italy
No full textSoil 222Rn concentrations have been monitored during the 2009 autumn and Spring 2010 rainy periods, in an alluvial soil, resting on a pyroclastic substrate (locally reworked), in the Pietramelara Plain, in Southern Italy. The dry soil diurnal oscillations detected at the site in August 2009 have been found to be present also during the rainy periods of the year, provided, however, that soil moisture conditions are not affected by rainfall infiltration or post storm gravity-driven percolation in the soil depth interval considered. With significant rainfall, the characteristic dry soil diurnal cycle is altered. This rainfall-induced perturbation produces a spike-like signal featuring a sharp rise, with commencement of precipitation, then followed, with persistent and significant rainfall, by an equally sharp drop to very low levels. Both the sharp rise, resulting from capping, and the sharp drop (wash-out), resulting from infiltration, have been found to follow not previously reported second-order trends tied to cumulative rainfall, with very high statistical significance (r2 > 0.97 for the sharp rise and r2 > 0.95 for the sharp drop). Furthermore, the sharp drop appears to be tied to wetting front migration of 222Rn-free, or 222Rn-poor, rainwater and to commence when it reaches the soil probe depth, effectively flushing and transferring radon to lower levels of the profile, thus validating previous studies. Low rainfall events (<1–2 mm), however, do not appear to alter significantly the dry soil diurnal cycle. Post rainstorm recovery of soil 222Rn concentrations, in the immediate aftermath of significant rainfall, appears to be very slow and limited. The spike-like pattern induced by rainstorm events poses significant questions as to the interpretation of soil 222Rn concentration time series data in geophysical precursor studies. Likewise the extreme variations resulting from rainfall, and likely affected by rainfall duration, intensity, frequency and spatial variability, pose significant implications in environmental monitoring studies aimed at characterising representative soil 222Rn concentration levels for the wet season
Are limnic eruptions in the CO2-CH4-rich gas reservoir of Lake Kivu (Democratic republic of the Congo and Rwanda) possible? Insights from physico-chemical and isotopic data
No full textAn overturn of Lake Kivu was seriously considered after the January 2002 Nyiragongo volcanic eruption, which erupted 20 × 106 m3 of lava from a NS-oriented fissure on the southern flank of the Congolese volcano. Part of this silica-undersaturated magma produced a lava flow that entered Lake Kivu down to a depth of 70-100 m. The possibility of a rollover comes from the fact that Lake Kivu is meromictic and below ≈250 m a CO2-CH4-rich gas reservoir is present. Thus, the riparian population (≈2,500,000 people) is endangered by a possible limnic eruption. During last 30 years several vertical profiles carried out by several researchers have evidenced a relatively pronounced vertical physico-chemical and isotopical variation. Nevertheless, saturation of CO2 and CH4 appears to be far from critical values, indicating that presently the hydrostatic pressure cannot presently be overcome. Recent studies have suggested an increase in dissolved gases (particular CH4) at depth and the uprising of the chemocline, a limnic eruption could possibly occur within 80-200 years from now. More studies are needed to follow up the lake evolution with time. Simulations will shed light on possible internal and external factors able to provoke the release a suffocating and, possibly, inflammable killer cloud. In this paper, we investigate using recent historical eruptive events of Nyiragongo volcano, we discuss the possibility that a limnic eruption may occur in a near future, although the stability of Lake Kivu is presently high: only exceptionally high magnitude events appear to be able to destabilize the 560 × 109 m3 water volume contained in its basin
Lithological Influence and Human Impact on the Hydrochemistry of an Apennine Watershed (Southern Italy)
No full textThis study focuses on chemical and physical parameters of the Calore Catchment (Italy), to identify the sources of surface and groundwater mineralization. The study also evaluates water quality variations due to potential anthropogenic contamination. The proposed approach is a suitable screening tool to gain information on upland catchment characterized by complex hydrogeological and structural settings
Origin and pattern of salinization in the Holocene aquifer of the southern Po Delta (NE Italy)
No full textThe origin and patterns of groundwater salinity of a shallow coastal aquifer pertaining to a reclaimed subsiding zone of the Po Delta are examined in this study. The aim is to identify the source of the hypersaline groundwater residing in the basal portion of the aquifer and to infer the mechanism of salinization of the remaining portion of the aquifer. To disentangle the possible sources of salinity the molar ratio of environmental tracers like Cl- and Br- were used in combination with the classical geochemical analyses of major and minor cations ratios. High-resolution multi-level sampling (MIS) allowed obtaining a robust and self-consistent hydrogeochemical database, which was statistically analysed via factor analysis and proved to be log-normally distributed. Thus, a common origin could be inferred for the elevated salinity that characterize most of the groundwater samples, this can be recognized in the organic rich fine-grained sediments, deposited in salty back barrier and marsh environments during the last transgression phase. This study proves that a detailed analysis of groundwater geochemistry can be considered a valuable tool to assess the origin of salinity in coastal Holocene aquifers, where the traditional conceptual model of a simple fresh/seawater interface may not be adequate. (C) 2017 Elsevier B.V. All rights reserved
Lithological Influence and Human Impact on the Hydrochemistry of an Apennine Watershed (Southern Italy)
Get PDFThis study focuses on chemical and physical parameters of the Calore Catchment (Italy), to identify the sources of surface and groundwater mineralization. The study also evaluates water quality variations due to potential anthropogenic contamination. The proposed approach is a suitable screening tool to gain information on upland catchment characterized by complex hydrogeological and structural settings
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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