1,721,048 research outputs found
Dynamic characteristics of sulfur, iron and phosphorus in coastal polluted sediments, north China
No full textThe cycling of sulfur (S), iron (Fe) and phosphorus (P) in sediments and pore water can impact the water quality of overlying water. In a heavily polluted river estuary (Yantai, China), vertical profiles of fluxes of dissolved sulfide, Fe2+ and dissolved reactive phosphorus (DRP) in sediment pore water were investigated by the Diffusive Gradients in Thin films technique (DGT). Vertical fluxes of S, Fe, P in intertidal sediment showed the availability of DRP increased while the sulfide decreased with depth in surface sediment, indicating that sulfide accumulation could enhance P release in anoxic sediment. In sites with contrasting salinity, the relative dominance of iron and sulfate reduction was different, with iron reduction dominant over sulfate reduction in the upper sediment at an intertidal site but the reverse true in a freshwater site, with the other process dominating at depth in each case. Phosphate release was largely controlled by iron reduction. (C) 2016 Elsevier Ltd. All rights reserved
Investigating the potential of sunflower species, fermented palm wine and Pleurotus ostreatus for treatment of petroleum-contaminated soil
Full text linkPhyto- and myco-remediation have been identified as sustainable options for treatment of petroleum-contaminated soils. To appraise the benefits thereof, the potentials of 3 sunflower species, 2 palm wine types and P. ostreatus to treat petroleum-contaminated soils was investigated. The study involved sampling of petroleum-contaminated soils and treatment with the phyto- and myco-remediation agents for a period of 90-days. Agents used for the remediation were 3 species of sunflowers (Helianthus annus-pacino gold, Helianthus sunsation & Helianthus annus-sunny dwarf), fermented palm wine (from 2 species of palm trees -Elaeis guineensis & Raffia africana), and oyster mushroom (Pleurotus ostreatus). The study further investigated variation in remediation efficiency among the sunflower and palm wine species, as well as different substrates and conditions for optimal application of P. ostreatus. The results obtained revealed up to 340 g/kg dry weight of Total petroleum hydrocarbons (TPHs) in the soils, with remediation outcomes of up to 69% by the sunflower- Helianthus annus (Pacino gold), 70% by fermented palm wine, and 85% by P. ostreatus. While the remediation efficiency of sunflower species was proportional to biomass, there was no significant difference in remediation efficiency of the palm wines. It was also found that substrates type and method of application has a significant impact on the remediation efficiency of P. ostreatus. The study further revealed available nitrate and electrical conductivity as possible useful indicators of TPHs concentration and remediation progress in soils. (C) 2019 Elsevier Ltd. All rights reserved
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Evidence for suboxic nitrification in recent marine sediments
Full text linkThe classical scheme of biogeochemical zones (BGZ) is known to be an oversimplification
of the microbial processes that occur in organic-rich marine sediments. Results from a coupled
deployment of pore-water gel probes in Loch Duich, Scotland, provide direct evidence for rapid
recycling within the iron reduction (FeR) and sulphate reduction (SR) zones. High resolution porewater
profiles obtained using diffusive equilibrium in thin films (DET) gel probes found a nitrate peak
at the boundary between the FeR and SR zones. This non-steady state feature is consistent with recycling
of reduced N occurring throughout the FeR zone. Both conventional pore-water iron profiles
and results from diffusive gradient in thin films (DGT) probes indicate that iron is solubilised and precipitated
in rapid Fe/S recycling reactions throughout the SR zone. The presence of such complex
recycling reactions confirms the oversimplification of the classical BGZ scheme
Mycoremediation of petroleum contaminated soils: progress, prospects and perspectives
Full text linkMycoremediation, an aspect of bioremediation, has been investigated for some decades. However, there seems to be little progress on its commercial application to petroleum-contaminated soils despite some promising outcomes. In this review, mycoremediation is examined to identify development, limitations and perspectives for its optimal utilization on petroleum-contaminated soils. Mycoremediation agents and substrates that have been used for the treatment of petroleum contaminated soils have been identified, application methods discussed, recent advances highlighted and limitations for its applications accentuated. Possible solutions to the challenges in applying mycoremediation to petroleum-contaminated soils have also been discussed. From this review, we conclude that for optimal utilization of mycoremediation of petroleum-contaminated soils, ideal environmental, edaphic and climatic factors of a typical contaminated site must be incorporated into the approach from first principles. Development of application procedures that can easily translate laboratory results to field applications is also required
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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