1,720,958 research outputs found
Long-term effects of heavy metals from composted municipal waste on some enzyme activities in a cultivated soil
No full textA 3-year field experiment on a calcareous Fluventic Xerochrept planted with corn (Zea mays L.) was carried out to evaluate the effects of amending the soil with high and low rates of composted municipal waste on soil enzyme activities (alkaline phosphomonoesterase, phosphodiesterase, arylsulphatase, dehydrogenase, and L-asparaginase). These enzyme activities all increased when compost was added at rates of up to 90 t ha-1, and the phosphatases continued to show a linear increase with compost rates of up to 270 t ha-1. The addition of mineral fertilizer increased enzyme activities in unamended soil, and masked the stimulating effect of compost on the amended soils. Heavy metals did not affect soil enzyme activities up to a compost addition of at least three times the amount specified by Italian law
Trace metals uptake and distribution in corn plants grown on a 6-year urban waste compost amended soil
No full textA 6-year field study was performed to evaluate heavy metal accumulation in the top 20 cm of a clay-loam calcareous soil (Fluventic Xerochrept) amended with urban waste compost and to determine heavy metal uptake and distribution in corn plants grown in this soil. Compared with untreated soils, amended soils showed a significant increase only in Cu, Zn, Pb and, in the last 2 years, Cr concentrations. The corn plants grown on the amended soil showed a general increase in metal uptake, which was about three times greater for Pb and two times greater for the other heavy metals than in plants grown on untreated soil. At times, the diluting effect resulting from enhanced growth rates of the plants with compost application resulted in lower concentrations in the plants grown on treated plots. Cr and Pb were less mobile in the corn plant and were accumulated only in root tissues. Only in the last 3 years of the experiment were traces of Pb found also in the stalks. The limited mobility of Pb was confirmed in a contemporary hydroponic greenhouse experiment. The values of the plant/soil transfer coefficients were within the lower range reported in the literature, indicating that in the soil studied (which contained 14% CaCO 3) there was limited transfer of heavy metal ions from the soil to the corn plants. It is concluded that the long-term application of large amounts of urban waste compost to CaCO3-containing soils does not necessarily cause medium-term problems to plant, animal or human health
Mobility of Heavy Metals in Urban Waste‐Amended Soils
No full textAbstract A soil column study was conducted to assess the vertical movement of certain heavy metals in soils amended with urban waste compost (90 t ha−1). The effect of the complexing capacity of water soluble organic matter from compost on metal mobility has been previously reported. The results of this investigation demonstrate the enhanced levels of Cu, Zn, Ni, and Cr eluted from 50-cm soil columns when compost is added to a Fluventic Xerochrept clay-loamy, mixed, mesic and a Typic Xerochrept, fine sandy-loamy, mixed, mesic. The increase in these metal concentrations is greater in sandy-loam soil than in clay-loam. The water soluble organic fraction of the compost has minimal impact on the metals concentration. Seventy to eighty percent of the water-soluble organic fraction was retained in the upper 10-cm layer of soils, with only 5% eluted from clay-loam soil and 10% from the sandy-loam
Coal ash as a substrate in hydroponics: chemical and agronomical aspects
No full textTomato plants were grown in hydroponics using pelleted fly and heavy ash as substrates. The water stability of the substrates and their ability in a nutrient, solution to sorb or desorb ions have been studied. Both substrates showed a satisfactory stability to water treatments. Interactions between the nutrient solution and the substrates did not influence the ion uptake by tomato plants nor plant growth and productivity
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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