1,720,992 research outputs found
Dust, Metals and Metalloids in the Environment: From Air to Hair .
No full textBillion tons of particulate matter, made up of inorganic and organic compounds, are released every year into the atmosphere, from both anthropogenic and natural sources. These latters, which include geogenic material from erosion, agriculture, sea spray and volcanic activity account for about 97% of the total mass of particles. The contribution of anthropogenic sources, about 3%, is more pronounced in industrialized and also in urban areas, where vehicular traffic is one of the most important sources. When examining the health impact, in addition to mass level and size, two other main characteristics of particulate matter need to be considered: its nature and chemical composition. These parameters appear intrinsically related one another. Presence, abundance and behavior of trace metals in air are also closely related to atmospheric particulate matter, as most metals in the lower atmosphere are present in association with particles. Most of these aspects are presented and discussed in the present article as only a better knowledge of atmospheric particulate matter, its composition, metal content and some implications on the human health, may aid to select correct actions and appropriate control strategies
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
The effect of CO2 scrubbing on δ13C-CO2 by mineral aquifers: implications for management of the resource.
No full textVariations 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
A geometrical method for quantifying endmembers' fractions in three-component groundwater mixing
Full text linkWe present a new geometrical method capable of quantifying and illustrating the outcomes of a three-component mixing dynamics. In a three-component mixing scenario, classical algebraic equations and endmember mixing analysis (EMMA) can be used to quantify the contributions from each fraction. Three-component mixing of natural waters, either in an element–element plot or by using the EMMA mixing subspace is described by a triangular shaped distribution of sample points where each endmember is placed on an apex, while each side corresponds to the mixing function of the two endmembers placed at the apex, considering the third endmembers' contribution equal to zero. Along each side, the theoretical mixing fractions can be computed using mass balance equations. Samples with contributions from three endmembers will plot inside the triangle, while the homogeneous barycentric coordinate projections can be projected onto the three sides. The geochemistry observed in the mineralized Ferrarelle aquifer system (southern Italy) results from three-component mixing of groundwater, each with diagnostic geochemical compositions. The defined boundary conditions allow us to parameterize and validate the procedures for modelling mixing, including selection of suitable geochemical tracers
Evaluating the suitability of urban groundwater resources for drinking water and irrigation purposes: an integrated approach in the Agro-Aversano area of Southern Italy
No full textDeterioration of groundwater quality due to the introduction of pollutants from natural and anthropic sources has become a major environmental issue. We tested three methodologies in assessing groundwater quality and intrinsic aquifer vulnerability in the Agro-Aversano area (Southern Italy). A geographic information system (GIS)-based groundwater quality index (GQI) was realized to assess groundwater quality for drinking and irrigation use and, in parallel, standard SINTACS was applied to evaluate the intrinsic vulnerability of the aquifer. Nitrate concentrations and sodium absorption ratio (SAR) in groundwater samples were used to verify the reliability of vulnerability data. GQI analysis pointed to a general poor quality of groundwater both for drinking and irrigation use, especially in sub-urban areas. The spatial pattern of water quality from GQI analysis was positively related to nitrate and fluoride concentrations for drinking use and to bicarbonate and sodium concentrations for irrigation use, whose levels exceeded the WHO and FAO recommended thresholds, respectively. Standard SINTACS was found to be inadequate for describing the aquifer state, its results showing no correlation with nitrate concentration or SAR. Because of this inconsistency, we tested a novel approach combining GQI with SINTACS analysis. Results showed positive correlation with nitrate (r = 0.63) and SAR (r = 0.64) contents, thus pointing to combined SINTACS-GQI as a more reliable approach than standard methodologies
Geochemical and isotopic evidences of magmatic inputs in the hydrothermal reservoir feeding the fumarolic discharges of Tacora volcano (northern Chile)
No full textTacora volcano is a nearly unknown and understudied 5980 m high volcano located on the northernmost
border between Chile and Peru. Tacora is characterized by intense fumarolic activity with extensive, whitecolored,
hydrothermal areas along the NW and W flanks of the volcanic structure. The chemical and isotopic
features of gas emissions indicate that the hydrothermal reservoir is significantly affected by contributions
from magmatic degassing, despite relatively low outlet temperatures (82–93 °C). Water and gas isotopic
signatures stem from degassing of andesitic magmas produced from the sediment-poor subducting slab.
Isotopic data suggests CH4–CO2 isotopic equilibration occurs at ~400 °C, likely in the deepest portion of the
hydrothermal-magmatic fluid reservoir. The H2–H2O, CO–CO2, H2–Ar, CH4–CO2 and C2–C3 alkenes/alkanes
pairs tend to approach a chemical equilibrium at temperatures between 200 and 320 °C when redox conditions
aremore oxidizing than those determined by the typical FeO/FeO1.5 rock buffer system. Boiling occurs at shallow
depth at 85 °C within a discontinuous, thin aquifer, enough as thermal buffer but not able to scrub the uprising
magmatic-related acidic gases
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