1,720,957 research outputs found
Natural and anthropogenic factors driving groundwater resources salinization for agriculture use in the Campania plains (Southern Italy)
Full text linkThe Mediterranean region is under pressure for a more sustainable use of water resources in view of the actual and future climate change. Under this pressure, the need to better assess the links between groundwater availability and quality and irrigated agriculture, is becoming urgent. Through the hydrogeologic and hydrochemical characterization of the coastal aquifers of a representative Mediterranean study area (the Campania Region in southern Italy), this study strengthened the analysis of basic components of the groundwater cycle and their temporal variability, including hydrologic, environmental and socio-economic aspects. Selected physiochemical properties of groundwater in 52 monitoring wells were considered from the Campania Environmental Protection Agency database. A total of 626 samples were collected from 2004 to 2018 to capture the water quality variability. Factor analysis and a specific groundwater quality index were also applied on 23 samples in two different timelines (2006, 2016) to capture the hydro-chemistry evolution through year. Moreover, land use and active pumping wells locations were used in the analysis. Spatial and temporal trends of base exchange indices (BEX) and sodium adsorption ratio (SAR) were computed along with Pearson coefficient among different variables, like well densities and distance from the coast. The variation in the distribution of salinity between 2006 and 2016, along with highly positive and highly negative BEX and groundwater quality index values, indicate unstable conditions for the future. In the greenhouse's areas, where groundwater exploitation is elevated, an increase of salinity was recorded due to seawater intrusion. In volcanic districts water rock interaction is the main driver of groundwater salinization, while mixing processes with carbonate freshwaters diminish groundwater salinities in the alluvial plains. This study demonstrates that groundwater over pumping can have a major impact on groundwater quality used for irrigation, despite the dominant influence that local geological and morphological features exert on the area
Soil conditioners effects on hydraulic properties, leaching processes and denitrification on a silty-clay soil
Full text linkAgricultural landscapes are often affected by groundwater quality issues due to fertilizers leaching. To address this worldwide problem several agricultural best practices have been proposed, like limiting the amount of fertilizers and increasing soil organic matter content. To evaluate if these practices may promote groundwater quality enhancement, vadose zone retention time and complex biogeochemical processes must be known in detail. In this study, sequential undisturbed column experiments were performed to determine the amount of nutrients and heavy metals leached after simulated stormwater events. The column was amended with urea then flushed for two pore volumes, then straw residuals were incorporated and flushed for two pore volumes and finally compost was incorporated and flushed for six pore volumes. Dissolved ions, major gasses and heavy metals were determined in leachate samples. Nitrate and nitrite were leached in the urea treatment producing the highest concentrations, followed by compost and straw residuals. The redox conditions were aerobic in all treatments and pH was circumneutral or slightly basic. Denitrification was low but increased with the addition of straw residuals and compost. Heavy metals were all at very low concentrations except for lead and cadmium, which slightly exceeded threshold limits (10 and 1 μg/L, respectively) in all the treatments. The compost treatment, after three pore volumes, was affected by clay swelling due to sodium dispersion, which in turn provoked a reduction of porosity and hydraulic conductivity
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
Nutrients and carbon fate in two lowland contrasting soils amended with compost
No full textThe present study investigated the transient effects of compost application combined with minimum tillage followed by traditional fertilization in two contrasting agricultural soils of the Po River plain, where both nutrients leaching and carbon cycle were monitored for three years (2016–2019) via several campaigns of soil and groundwater sampling and gas emissions. The results of this work highlight that the effects of compost on nutrients leaching is transient and is soon lessened over time if new incorporations do not take place. Nutrients leaching was minimal on shallow groundwater quality with the following decreasing order: nitrate > ammonium > nitrite > phosphate. Moreover, the nutrients distribution profiles (nitrate, nitrite, ammonium and phosphate) also depended on the groundwater fluxes and on boundary conditions (geogenic sources and previous fertilizations). The soil organic carbon results highlight that its increase (approximately 1 ± 0.4% in both soils) was temporary and was not anymore discernible after three years since compost incorporation. The carbon dioxide emissions behave like the soil organic carbon, with an initial increase (approximately 66 ± 17 mM/m2/d in both soils) due to mineralization and a subsequent decrease, while no methane and hydrogen sulphide emission were detected. Moreover, carbon dioxide fluxes were also driven by the soil with nearly doubled fluxes in the site with a higher soil organic carbon baseline
Unravelling the salinity origins in the coastal aquifer/aquitard system of the Volturno River (Italy)
No full textTo counteract the ongoing salinization of coastal aquifers, which poses a significant environmental and socioeconomic challenge to local communities, it is necessary to first understand the origin and mechanisms of this phenomenon. This study investigates the origins of salinity in the Volturno River lowland in Southern Italy and reveals that the primary source in the area is paleo-seawater entrapped within sediments that were subject to evapoconcentration processes. By systematically collecting sediment samples at variable depths and locations and extracting porewaters, a comprehensive understanding of the interplay between freshwater and saline water was gained, including complex patterns of vertical stratification of groundwater salinity. The study highlights the limitations of traditional methods that rely on salinity monitoring via integral depth sampling, particularly in capturing the vertical redox and salinity gradients characteristics of layered aquifer/aquitard systems. On the contrary, environmental tracers, like chloride and bromide, provide valuable insights into the sources of groundwater salinity, distinguishing between current seawater intrusion and other causes, such as paleoseawater and return flow from drained agricultural land. Results suggest that the majority of salinity does not originate from modern seawater intrusion or recent evaporation. Instead, it can be attributed to paleo-seawater affected by evapoconcentration processes. This study has broader implications for the sustainable management of coastal aquifers and the safeguarding of freshwater resources. While our findings are specific to the Volturno River coastal area, the methodologies and insights here presented can be reproduced in every coastal region facing similar salinity challenges
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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