1,721,073 research outputs found
Thermal analysis for the evaluation of the organic matter evolution during municipal solid waste aerobic composting process
No full textA study aimed to monitor the composting process and to evaluate the effectiveness of indicators able to define the stability of a compost obtained by mixing municipal solid waste (MSW) and vegetal waste, was conducted. For this reason, composting process lasting 3 months, was monitored by chemical and thermal analysis. Total organic carbon (TOC), total extractable carbon (TEC) and humic and fulvic acid carbon (HA and FA, respectively) were determined after extraction, fractionation and analysis of organic matter from samples collected during the composting process. Differential scanning calorimetry (DSC), thermogravimetry (TG) and the first derivative of the TG (DTG) were simultaneously performed in oxidizing conditions on grounded compost samples and HA extracted. Thermoanalitical data resulted to be useful in integrating quantitative information coming from chemical analysis of humified fraction of compost organic matter. Particularly DSC curves allowed to distinguish between well and poor stabilized organic matter, and information deriving from weight losses, registered by the TG and DTG curves, enable to individuate the evolution state of the organic matter and therefore its stability
Growth and yield characteristics and heavy metals content on tomatoes grown in different growing media
No full textThis work studied the effects that different growing media (compost and beached Posidonia oceanica) have on the growth, yield, and heavy metals concentrations of tomatoes (Lycopersicon esculentum Mill.) hydroponically grown in a greenhouse. A commercial substrate exclusively composed of pumice was used as a control sample. The choice of beached Posidonia oceanica as a growing media and as a matrix in order to obtain compost is due to the extraordinary accumulation of deposits of the seaweed Posidonia oceanica on the beaches of Sardinia and in general on the beaches of countries of the Mediterranean. Leafy deposits of Posidonia oceanica are treated as refuse and disposed off in waste dumps. In fact, the Italian law prevents the agricultural use of beached P. oceanica plants considering them as heavy metal accumulators and then, a cause of heavy metals contamination in the environment. Nevertheless, it is important to pay great attention to physical and chemical characteristics of the growing media used in order to avoid soil pollution and the danger of introducing harmful substances in the food chain. Growth and yield parameters were calculated during the different stages of plant growth. The total concentrations of some heavy metals [lead (Pb), cadmium (Cd), zinc (Zn), chromium (Cr), copper (Cu)] were determined in growing media, tomato fruits, and in leaves. No statistically significant differences were found between the growth and yields of plants grown in different growing media. The heavy metal concentrations of compost were higher than those of beached Posidonia oceanica or the control sample. However, most metals strongly interacted with the organic matter of compost, limiting the vegetal absorption. Metals concentration in fruits and leaves was essentially the same in all the plants. According to these observations the use of compost and beached Posidonia oceanica as growing media did not cause a metals accumulation in fruits and plants of tomatoes grown in hydroponics
Composting of Posidonia oceanica and its use in agriculture
No full textThe extraordinary accumulation of deposits of the seaweed Posidonia oceanica on the beaches of Sardinia has given rise to a series of problems linked to its disposal. Leafy deposits of Posidonia oceanica are treated as refuse and disposed of in waste dumps. This is an enormous waste of organic material.
Bearing this in mind, some composting experiments have been carried out using washed Posidonia oceanica, sludge and woody residues. The selected substrates were categorised and then mixed homogeneously, according to the previously established parameters, to obtain different mixtures which would satisfy the preliminary physical and chemical conditions for correct composting. The experiment was conducted using an open system with natural ventilation.
The final assessment of the chemical parameter values of the compost showed a good carbon, nitrogen and phosphorus content and a balanced ON ratio. The degree of humification was raised appreciably, which indicated that the material had reached a high level of stability. The parameters for the physical characteristics (porosity, apparent density, easily available water and reserve water, etc.) were within the acceptable limits. No pathogenic microorganisms were found, which indicates that the compost was healthy, and the heavy metal content, in particular that of thallium, cadmium, chromium and lead, was below the levels established by law. These results offer an innovative solution to the disposal of Posidonia oceanica which would otherwise be taken to waste dumps, and offers undoubted advantages for the coastal communities interested in this problem
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
Evaluation of the interaction mechanisms between red muds and heavy metals
No full textThis paper investigated the heavy metal adsorption of non-treated (RMnt) and acid-treated red muds (RMa), bauxite ore processing waste, in order to evaluate how efficient they are in reducing metal solubility and bioavaliability in polluted soils. Red mud samples were artificially polluted with solutions containing increasing concentrations of Pb, Cd and Zn. Cancrinite and hematite were the main phases of the red muds, and were also the components which adsorbed most heavy metals. The results showed that the RMnt adsorption capacity for the three heavy metals was Zn ≥ Pb > Cd. Acid treatment with HCl decreased the red mud's capacity to adsorb the heavy metals by 30%.
In order to study the different heavy metal–RM interaction mechanisms, all samples after artificial contamination were treated with solutions with gradually increasing extraction capacity. H2O and Ca(NO3)2 treatments only extracted very low concentrations of Pb, Cd and Zn, while EDTA treatment extracted the most adsorbed heavy metals from the sorbent particles. In particular the water-soluble and exchangeable metal fractions were higher in the RMa than they were in the RMnt, while the concentrations of Pb, Cd and Zn extracted with EDTA were lower.
The results showed that red muds can be used successfully to reduce the solubility and bioavailability of heavy metals in polluted soils
L'ipogeismo nel Mediterraneo. Origine, sviluppo e quadri culturali
No full textL'opera raccoglie i contributi di studiosi provenienti da diversi paesi europei; essi offrono un quadro articolato del fenomeno dell'ipogeismo e delle tematiche ad esso connesse: genesi, cronologia, architettura, aspetti simbolici
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
Evolution of heavy metals mobility during municipal solid waste composting
No full textThe influence of municipal solid waste composting on the concentration, water solubility, and phase association of Pb, Cd, Zn and Cu at high concentrations in the starting materials, was studied. The evolution of some chemical parameters (total organic carbon, humic and fulvic acid, water-soluble fraction of organic carbon) during composting was examined to establish their influence on heavy metal speciation. Changes of solubility and potential bioavailability of the analyzed heavy metals were investigated using sequential extraction procedure [i.e. water, 0.1 N Ca(NO3)2 and EDTA]. The Cd, Cu and Zn concentrations slightly decreased during composting due to leaching losses (9.3%, 3.7% and 1.1%, respectively), whereas Pb total concentration did not vary. The progressive decrease in total metal concentration was accompanied by a corresponding decrease in the amounts of water-extractable metals. The water-extractable fractions of Pb and Cu decreased rapidly during composting (losses of 95% and 100%, respectively). The decreases in water-extractable Cd and Zn were lower (losses of 60%). Generally, changes in the water-soluble fractions of metals were reflected by the concentrations of water-soluble organic carbon. The evolution of humic fractions also appeared to be important in determining the solubility of heavy metals. The results obtained showed that during composting the heavy metals in the starting materials have been redistributed from more labile and soluble forms to more stabilized ones
EVALUATION OF CORK COMMERCIAL QUALITY THROUGH N2 ADSORPTION AND MERCURY INTRUSION POROSIMETRY
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