1,720,989 research outputs found
Impact of biochar on herbicide pollution in the litani river Basin
No full textThe Litani River, the largest in Lebanon, suffers from different kind of pollution including that caused by pesticides. Among the herbicides, Fluazifop (FLP), Terbuthylazine (TBZ) and Triclopyr (TCP) are the most used and therefore the sorption on sediment and soil samples from four sites along Litani river basin: Berdaouni, Joub Jannine, Aammiq and Qaraoun, was investigated. For the three herbicides and on all sediment and soil samples, the sorption data, fitted to Freundlich logarithmic equation, show very low Kads values. At sediment and soil pH values, the herbicides and sediment and soil colloids are negatively charged, therefore negative sorption should be expected. Nevertheless, the sorption observed suggest that a lipophilic effect is acting. FLP, TBZ and TCP are herbicides with a high risk of leaching. The addition of biochar (BC) to soils and sediments increases considerably Kads values of BC added sediments and soils in comparison with that of BC-free samples. Moreover, desorption is not observed suggesting that the sorption is not reversible and hysteresis occurs. These findings suggest that the BC soil addition in Litani river basin area may be considered as an useful tool to prevent FLP, TBZ and TCP leaching in this polluted region of Lebanon
Assessment of biochars obtained at two different pyrolysis temperatures to mitigate pollution due to Lumax®
No full textNew strategies, such as biochar soil amendment, are continuously developed to restore the agricultural environment from the adverse effects of agrochemicals. The sorption efficiency of a biochar depends on the specific raw materials and pyrolysis variables applied, such as temperature and heating time, that shape its physico-chemical properties. In this study, the sorption capacity of two biochars obtained from coppiced hardwoods at two different pyrolysis temperatures ( 6 5 0 C and 1100 C, denominated BCLT and BCHT, respectively) was assessed for Lumax®, a pre-emergence selective herbicide used for maize cultivation. Lumax® is composed of S-metolachlor (MTC), terbuthylazine (TBZ), and mesotrione ( M S T ) , therefore the sorption behaviour of active ingredients, alone or mixed as in the commercial formulation, was studied on two biochar samples to identify the best product to mitigate Lumax® pollution. Our results show that, although biochar performance depends on the physicochemicals properties of both the biochar and the pollutants, B C H T was the most suitable in retaining the Lumax® active ingredients, likely due to its high aromaticity
Effect of exogenous dissolved organic matter on fenhexamid adsorption by soils
No full textFenhexamid (N-(2,3-dichloro-4-hydroxyphenyl)-1-methyl-cyclohexanecarboxamide, Teldor®) is a fungicide representative of the new chemical class of hydroxanilides. It is a locosystemic compound with excellent activity against B. cinerea. Dissolved organic matter (DOM) plays an important role on the mobility of pollutants in environment. The aim of this study was to investigate fenhexamid adsorption on soils after addition of DOM coming from different composts. Two soils were chosen, a calcareous soil with low organic matter (OM) content and an acidic soil rich in OM.
The empirical Freundlich equation describes well the adsorption behaviour of fenhexamid on soils. The adsorption isotherms on calcareous soil resemble L-type isotherms characteristic of a high affinity of the fungicide for the adsorption sites. The adsorption on acidic soil shows a C-type isotherm suggesting a constant partitioning of adsorbate between solution and adsorbent sites. In general, the DOM addition to soils increases fenhexamid adsorption. In fact, the Freundlich constant (KF) increases from 4.86 to 6.70-8.16 on calcareous soil and from 35.2 to 44.1-49.2 on acidic soil. FT-IR spectra indicate that the fungicide does not undergo significant changes as a consequence of the adsorption. These findings are indicative of a weak interaction like a hydrophobic bond. The fungicide adsorption on soils is hysteretic and the amount of fenhexamid desorbed by water decreases as the soil OM content increases. Fenhexamid is scarcely soluble in water because of its scarcely polar character, therefore water is not suitable as extracting solvent. A strong increase of desorbed fenhexamid is obtained using dichloromethane as desorbing solvent
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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