1,720,956 research outputs found
A 16th century artificial reservoir under human pressure: water quality variability assessment in Laguna de Yuriria, central Mexico
No full textThis study assesses the variability of physicochemical and biochemical parameters, identifies principal pollutant sources, and characterizes water quality in Yuriria reservoir using water quality indexes in combination with multivariate statistical techniques. In situ parameters were measured in 55 reservoir sites including surface and deep points and in 7 associated channels. Moreover, major compounds and biochemical data were determined. Yuriria reservoir had alkaline, bicarbonate-mixed waters, with total dissolved solids (TDS) of 393.83 ± 3.43 mg L−1. Water quality index (WQI) indicated a good class for agricultural irrigation but very poor and poor classes for preservation of aquatic life. The nutrient inputs and the internal nitrogen recycling triggered a hypereutrophic status in the reservoir. The decomposition of residual biomass from aquatic macrophytes contributed to reduce dissolved oxygen (DO) in the hypolimnetic waters (mean DO = 3.86 mg L−1). Statistical analysis revealed that the study area is highly exposed to anthropogenic stress and in a lesser extent to natural processes. Urban and agriculture runoff enhanced the salinization and the generation of solid particles which deteriorated water quality. Chemical oxygen demand (COD), biochemical oxygen demand (BOD), and NO3−-N presented a common anthropogenic origin by external (point and diffuse) and internal pollution sources, while a diffuse source (agricultural activities) was reveled for phosphorus. This study is important to be used in systematic monitoring and sustainable co-management programs and for formulating the necessary strategies to remediate the Yuriria reservoir water quality and extrapolate to other reservoirs worldwide.Fil: Zanor, Gabriela A.. Universidad de Guanajuato; MéxicoFil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Puy y Alquiza, María Jesús. Universidad de Guanajuato; MéxicoFil: Saldaña Robles, Adriana. Universidad de Guanajuato; MéxicoFil: Manjarrez Rangel, Cinthya Soledad. Universidad de Guanajuato; MéxicoFil: Rubio Jiménez, Carlos Alberto. Universidad de Guanajuato; MéxicoFil: Pussetto, Nathalie. Instituto Nacional del Agua. Subgerencia Centro de la Región Semiárida; Argentin
Surface hydrochemical dynamic in an artificial lake with anthropic impact: La Purísima reservoir, Central Mexico
Full text linkIn the present study, the hydrochemical dynamic and the water quality of La Purísima reservoir, Central Mexico, have been determined. The reservoir presents total dissolved solids (TDSs) between 146 and 328 mg L−1 and water quality neutral to slightly alkaline (pH 7.0 to 8.7) during the dry season, whereas it becomes clearly alkaline (pH 8.1–9.9) in the rainy-warm season. Through its main tributaries, La Purísima reservoir has been receiving water affected by anthropic activities, such as mining, urbanization, and agriculture. La Purísima reservoir indicates water quality suitable for irrigation and aquatic lives, but unsuitable for drinking purposes. A geochemical evolution from the riverine to the lacustrine zone is evidenced by the complexation of several free ions: the higher saturation indexes; the lower toxic metal concentrations; and the lower trophic status, which ameliorate the water quality in the lacustrine zone. Trace elements co-precipitate and are adsorbed onto bottom sediments. During summer, high evaporation rates and atmospheric precipitation are found to decline the water quality. Cluster analyses reflect the geo-setting and different pollution levels: urban impact from the north coast, and agricultural activities from the east coast. The sensitivity of the lake to geochemical behavior can be used to understand the complex dissolved geochemical dynamics in a lake and the potential effects from long-term anthropic impact variability. The information about water quality of La Purísima reservoir may be useful to preserve the ecosystem and its biodiversity.Fil: Lecomte, Karina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Pasquini, Andrea Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Manjarrez Rangel, Cinthya Soledad. Universidad de Guanajuato; MéxicoFil: Puy Alquiza, María Jesús. Universidad de Guanajuato; MéxicoFil: Segoviano Garfias, José de Jesús N.. Universidad de Guanajuato; MéxicoFil: Zanor, Gabriela Ana. Universidad de Guanajuato; México. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Analysis of environmental proxies in recent sedimentary records from reservoirs in central Mexico
Full text linkFil: Manjarrez-Rangel, Cinthya Soledad. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Halac, Silvana Raquel. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones en Ciencias de La Tierra; Argentina.Fil: Halac, Silvana Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Piovano, Eduardo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones en Ciencias de La Tierra; Argentina.Fil: Piovano, Eduardo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Del Rincón Castro, María Cristina. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Del Rincón Castro, María Cristina. Universidad de Guanajuato. División de Ciencias de la Vida. Departamento de Alimentos, Irapuato, Guanajuato; México.Fil: Miranda Avilés, Raúl. Universidad de Guanajuato. División de Ingenierías. Departamento de Ingeniería en Minas, Metalurgia y Geología, Irapuato, Guanajuato; México.Fil: Zanor, Gabriela Ana. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Zanor, Gabriela Ana. Universidad de Guanajuato. División de Ciencias de la Vida. Departamento de Ciencias Ambientales, Irapuato, Guanajuato; México.Con el objetivo de analizar y comparar los cambios en la dinámica ambiental en la Laguna de
Yuriria (LY) y la presa La Esperanza (PLE) se extrajeron núcleos sedimentarios cortos y se efectuó un análisis multi-indicador junto con el cálculo de índices geoquímicos. Las concentraciones de los elementos traza se compararon con los lineamientos internacionales de calidad de sedimentos para la protección de la vida acuática. Los sedimentos correspondientes a las últimas décadas de la LY indicaron un incremento progresivo en la productividad primaria, evidenciado por los contenidos elevados de carbono orgánico total (COT), derivados de clorofila (DC), carotenoides totales (CT) y fósforo total (PT), relacionado probablemente al aumento de urbanización, descargas de aguas residuales y actividades agrícolas. La zona oeste de la LY presentó valores más elevados de CT indicando un aporte de vegetación acuática vascular (lirio acuático). En cambio, la zona norte y este de la LY mostró valores más altos de DC videnciando una productividad primaria alta, asociada a florecimientos algales. Una correlación positiva entre COT y CIT (carbonoinorgánico total) en los registros de la LY sugiere la precipitación bioinducida de carbonatos. El As mostró concentraciones elevadas en los sedimentos de la LY, lo cual podría ser atribuído al uso de agroquímicos en la región, con posibles efectos adversos para la biota acuática. Por otra parte, la correlación positiva entre COT y PT en los sedimentos de la PLE evidenciaron un aporte de materia orgánica exógena que podría asociarse a la deforestación en la cuenca hidrológica. Se demostró una contaminación por Cr y Zn en la
PLE, los cuales serían probablemente aportados por fuentes geogénicas, mientras que el Cu y el As tendrían un probable origen antropogénico (minería). El Cu, el Cr, el As y el Pb revelaron
posibles efectos adversos para la biota acuática. Este estudio permitió evaluar el estado de los
procesos de contaminación en ambos reservorios y demostró que las secuencias sedimentarias son herramientas útiles para estudiar la dinámica ambiental a nivel espacial y vertical, lo que puede utilizarse para mejorar la gestión y cogestión de los reservorios.Abstract: This study analyses and compares changes in environmental dynamics in Laguna de Yuriria (LY) and La Esperanza (PLE) reservoirs. For this purpose, short sediment cores were extracted, and a multi-proxy environmental analysis was performed together with the calculation of geochemical indices. Trace element concentrations were compared with international sediment quality guidelines for the protection of aquatic life. The sediments corresponding to the last decades of the LY indicated a progressive increase in primary productivity, evidenced by elevated contents of
total organic carbon (TOC), chlorophyll derivatives (CD), total carotenoids (TC) and total
phosphorus (TP) in the last years, which is likely related to increased urbanization, wastewater
discharges and agricultural activities. While the northern and eastern zones of the LY have greater
CD values indicating a high primary productivity linked to algal blooms, the western part of the LY
has higher TC values reflecting a contribution of aquatic vascular plants (water hyacinth). The
positive correlation between TOC and TIC (total inorganic carbon) in the LY record indicates that
carbonate precipitation is caused by biological processes. Regarding trace elements, As showed
elevated concentrations in the LY sediments, probably associated with the use of agrochemicals
in the region, and with potential adverse effects on aquatic biota. On the other hand, the positive
correlation found in the sediments of PLE between TOC and TP indicates the contribution of exogenous organic matter, most likely as a result of the hydrological basin’s deforestation. Contamination by Cr and Zn was demonstrated in the PLE, which would be contributed by geogenic sources, while Cu and As would have an anthropogenic origin (mining). Cu, Cr, As and Pb revealed potential negative effects on aquatic biota. This research allowed us to assess the status of contamination processes in both reservoirs and demonstrated that the sedimentary sequences serve to document the environmental dynamics at a spatial and vertical scale that can be used to improve the management and co-management of the reservoirs.info:eu-repo/semantics/publishedVersionFil: Manjarrez-Rangel, Cinthya Soledad. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Halac, Silvana Raquel. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones en Ciencias de La Tierra; Argentina.Fil: Halac, Silvana Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Piovano, Eduardo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones en Ciencias de La Tierra; Argentina.Fil: Piovano, Eduardo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Del Rincón Castro, María Cristina. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Del Rincón Castro, María Cristina. Universidad de Guanajuato. División de Ciencias de la Vida. Departamento de Alimentos, Irapuato, Guanajuato; México.Fil: Miranda Avilés, Raúl. Universidad de Guanajuato. División de Ingenierías. Departamento de Ingeniería en Minas, Metalurgia y Geología, Irapuato, Guanajuato; México.Fil: Zanor, Gabriela Ana. Universidad de Guanajuato. División de Ciencias de la Vida, Irapuato, Guanajuato; México.Fil: Zanor, Gabriela Ana. Universidad de Guanajuato. División de Ciencias de la Vida. Departamento de Ciencias Ambientales, Irapuato, Guanajuato; México
Analysis of environmental proxies in recent sedimentary records from reservoirs in central Mexico
No full textCon el objetivo de analizar y comparar los cambios en la dinámica ambiental en la Laguna de Yuriria (LY) y la presa La Esperanza (PLE) se extrajeron núcleos sedimentarios cortos y se efectuó un análisis multi-indicador junto con el cál- culo de índices geoquímicos. Las concentraciones de los elementos traza se compararon con los lineamientos internacionales de calidad de sedimentos para la protección de la vida acuática. Los sedimentos correspondientes a las últimas déca- das de la LY indicaron un incremento progresivo en la productividad primaria, evidenciado por los contenidos elevados de carbono orgánico total (COT), derivados de clorofila (DC), carotenoides totales (CT) y fósforo total (PT), relacionado probablemente al aumento de urbanización, des- cargas de aguas residuales y actividades agrícolas. La zona oeste de la LY presentó valores más ele- vados de CT indicando un aporte de vegetación acuática vascular (lirio acuático). En cambio, la zona norte y este de la LY mostró valores más altos de DC evidenciando una productividad primaria alta, asociada a florecimientos algales. Una correlación positiva entre COT y CIT (carbono inorgánico total) en los registros de la LY sugiere la precipitación bioinducida de carbonatos. El As mostró concentraciones elevadas en los sedimentos de la LY, lo cual podría ser atribuído al uso de agroquímicos en la región, con posibles efectos adversos para la biota acuática. Por otra parte, la correlación positiva entre COT y PT en los sedimentos de la PLE evidenciaron un aporte de materia orgánica exógena que podría asociarse a la deforestación en la cuenca hidrológica. Se demostró una contaminación por Cr y Zn en la PLE, los cuales serían probablemente aportados por fuentes geogénicas, mientras que el Cu y el As tendrían un probable origen antropogénico (minería). El Cu, el Cr, el As y el Pb revelaron posibles efectos adversos para la biota acuática. Este estudio permitió evaluar el estado de los procesos de contaminación en ambos reservorios y demostró que las secuencias sedimentarias son herramientas útiles para estudiar la dinámica ambiental a nivel espacial y vertical, lo que puede utilizarse para mejorar la gestión y cogestión de los reservorios.This study analyses and compares changes in environmental dynamics in Laguna de Yuriria (LY) and La Esperanza (PLE) reservoirs. For this purpose, short sediment cores were extracted, and a multi-proxy environmental analysis was performed together with the calculation of geochemical indices. Trace element concentrations were compared with international sediment quality guidelines for the protection of aquatic life. The sediments corresponding to the last decades of the LY indicated a progressive increase in primary productivity, evidenced by elevated contents of total organic carbon (TOC), chlorophyll derivatives (CD), total carotenoids (TC) and total phosphorus (TP) in the last years, which is likely related to increased urbanization, wastewater discharges and agricultural activities. While the northern and eastern zones of the LY have greater CD values indicating a high primary productivity linked to algal blooms, the western part of the LY has higher TC values reflecting a contribution of aquatic vascular plants (water hyacinth). The positive correlation between TOC and TIC (total inorganic carbon) in the LY record indicates that carbonate precipitation is caused by biological processes. Regarding trace elements, As showed elevated concentrations in the LY sediments, probably associated with the use of agrochemicals in the region, and with potential adverse effects on aquatic biota. On the other hand, the positive correlation found in the sediments of PLE between TOC and TP indicates the contribution of exogenous organic matter, most likely as a result of the hydrological basin?s deforestation. Contamination by Cr and Zn was demonstrated in the PLE, which would be contributed by geogenic sources, while Cu and As would have an anthropogenic origin (mining). Cu, Cr, As and Pb revealed potential negative effects on aquatic biota. This research allowed us to assess the status of contamination processes in both reservoirs and demonstrated that the sedimentary sequences serve to document the environmental dynamics at a spatial and vertical scale that can be used to improve the management and co-management of the reservoirs.Fil: Manjarrez Rangel, Cinthya Soledad. Universidad de Guanajuato; MéxicoFil: Halac, Silvana Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Piovano, Eduardo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: del Rincon Castro, María Cristina. Universidad de Guanajuato; MéxicoFil: Miranda Aviles, Raúl. Universidad de Guanajuato; MéxicoFil: Zanor, Gabriela Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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
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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