1,721,209 research outputs found
Identifying pollution sources of sediment in Lake Jangseong, Republic of Korea, through an extensive survey: Internal disturbances of past aquaculture sedimentation
No full textLake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a “hotspot” site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (13C and 15N) of organic matter suggested that the pollutants in the sediments at the “hotspot” sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.11Nsciescopu
RAPID ANALYSIS OF ANABOLIC STEROIDS IN URINE SAMPLES BY ELECTROSPRAY TANDEM MASS SPECTROMETRY TOM BOMBAR
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A Preliminary Report on the Gonadal Development of Adult Milkfish, Chanos Chanos , Reared in Tanks
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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
Enhanced oxidative activity of zero-valent iron by citric acid complexation
No full textIn this study, we systematically investigated the oxidative degradation of 4-chlorophenol (4-CP) using nano zero valent iron (nZVI, Fe-0) cooperated with citric acid (CA), and the role of CA as well as the mechanism of oxidation were deeply evaluated. 56.2% of 4-CP was removed after 60 min under dark condition without any ventilation of oxygen in the presence of Fe0 and CA. The addition of CA accelerated the release of ferrous ions and promoted the Fenton reaction to generate much more reactive oxygen species (ROS), which was confirmed by EPR. The MINEQL+ 4.6 soft was utilized to calculated the existent species in Fe-0-CA system, and Fe(II)[Cit](-) was found to be the key species playing an important role on the degradation of 4-CP. Fe(II)[Cit](-) adsorbed on iron surface accelerated the transportation of electron from Fe-0 to O-2 to produce more % OH. This study puts forward the possible mechanism of generating ROS on Fe-0 enhanced by CA and provides an application for the oxidation of pollutants.11Nsciescopu
Oxidative degradation of benzoic acid using Fe0- and sulfidized Fe0-activated persulfate: A comparative study
No full textImplications of sulfidized Fe-0(nFe/FeS) for the abatement of pollutants of various categories are widely established. In this study, degradation of one of the major organic pollutants, benzoic acid (BA), has been performed using persulfate activated with nFe/FeS. Complete degradation of BA and its transformed product, hydroxybenzoic acid, was observed within 6 min. When the degradation was performed at alkaline pH, the degradation decreased to 8% in the case of Fe-0, but nFe/FeS still showed 100% degradation after 60 min. Iron dissolution and persulfate decomposition in the presence of scavengers showed that both sulfate and hydroxyl radicals were involved in the Fe-0-persulfate system and that the hydroxyl radicals were the major species in the nFe/FeS-persulfate system. The major degradation pathway of benzoic acid was hydroxylation followed by complete mineralization, as supported by the practical removal of total organic carbons (more than 75% within 15 min). The observed results are promising in using perstlfate activated by nFe/FeS for the remediation of various micro-pollutants from a multitude of water sources. (C) 2017 Elsevier B.V. All rights reserved.1195sciescopu
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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