990 resultados para degradation processes


Relevância:

60.00% 60.00%

Publicador:

Resumo:

Using the Geographic Information System (GIS) and taking into account its capability to analyze spatial data, a database of updated spatial data from the sub-basin of the Descalvado stream, Botucatu, SP, was developed to provide an evaluation and diagnosis of the area concerning land use and the degradation processes therein. Through GIS, priority areas for forest recovery were defined by Multicriteria Evaluation and using the Ordered Weighted Average method. The latter allows the decision maker to define the area to be recovered, facing limitation of resources, among one of the proposed scenarios, or do it in stages. The study showed that there are accelerated erosion processes in the headwaters of the springs of water bodies; there is also fragmentation of native vegetation, especially in hillside areas, and little presence of native vegetation in riparian areas. The application of the multicriteria analysis using the Ordered Weighted Average was important as it systematized and discriminated scenarios of priority for forest recovery.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Contamination by butyltin compounds (BTs) has been reported in estuarine environments worldwide, with serious impacts on the biota of these areas. Considering that BTs can be degraded by varying environmental conditions such as incident light and salinity, the short-term variations in such factors may lead to inaccurate estimates of BTs concentrations in nature. Therefore, the present study aimed to evaluate the possibility that measurements of BTs in estuarine sediments are influenced by different sampling conditions, including period of the day (day or night), tidal zone (intertidal or subtidal), and tides (high or low). The study area is located on the Brazilian southeastern coast, Sao Vicente Estuary, at Pescadores Beach, where BT contamination was previously detected. Three replicate samples of surface sediment were collected randomly in each combination of period of the day, tidal zone, and tide condition, from three subareas along the beach, totaling 72 samples. BTs were analyzed by GC-PFPD using a tin filter and a VF-5 column, by means of a validated method. The concentrations of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) ranged from undetectable to 161 ng Sn g(-1) (d.w.). In most samples (71%), only MBT was quantifiable, whereas TBTs were measured in only 14, suggesting either an old contamination or rapid degradation processes. DBT was found in 27 samples, but could be quantified in only one. MBT concentrations did not differ significantly with time of day, zones, or tide conditions. DBT and TBT could not be compared under all these environmental conditions, because only a few samples were above the quantification limit. Pooled samples of TBT did not reveal any difference between day and night. These results indicated that, in assessing contamination by butyltin compounds, surface-sediment samples can be collected in any environmental conditions. However, the wide variation of BTs concentrations in the study area, i.e., over a very small geographic scale, illustrates the need for representative hierarchical and composite sampling designs that are compatible with the multiscalar temporal and spatial variability common to most marine systems. The use of such sampling designs will be necessary for future attempts to quantitatively evaluate and monitor the occurrence and impact of these compounds in nature

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Deep-sea whale falls create sulfidic habits Supporting chemoautotrophic communities, but microbial processes underlying the formation Of Such habitats remain poorly evaluated. Microbial degradation processes (sulfate reduction, methanogenesis) and biogeochemical gradients were studied in a whale-fall habitat created by a 30 t whale carcass deployed at 1675 m depth for 6 to 7 yr on the California margin. A variety of measurements were conducted including photomosaicking, microsensor measurements, radio-tracer incubations and geochemical analyses. Sediments were Studied at different distances (0 to 9 in) from the whale fall. Highest microbial activities and steepest vertical geochemical gradients were found within 0.5 m of the whale fall, revealing ex situ sulfate reduction and in vitro methanogenesis rates of up to 717 and 99 mmol m(-2) d(-1), respectively. In sediments containing whale biomass, methanogenesis was equivalent to 20 to 30%, of sulfate reduction. During in vitro sediment studies, sulfide and methane were produced within days to weeks after addition of whale biomass, indicating that chemosynthesis is promoted at early stages of the whale fall. Total sulfide production from sediments within 0.5 m of the whale fall was 2.1 +/- 3 and 1.5 +/- 2.1 mol d(-1) in Years 6 and 7, respectively, of which similar to 200 mmol d(-1) were available as free sulfide. Sulfate reduction in bones was much lower, accounting for a total availability of similar to 10 mmol sulfide d(-1). Over periods of at least 7 yr, whale falls can create sulfidic conditions similar to other chemosynthetic habitats Such as cold seeps and hydrothermal vents.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

[EN] The presence of emerging contaminants has been previously described in reclaimed water and groundwater of Gran Canaria (Spain). Despite of the environmental risk associated to irrigation with reclaimed water (R), this practice is necessary considering sustainability of the hydrological cycle in semiarid zones, especially regarding agricultural activity. The aim of this study was: i) to analyse the evolution during two years of contaminants of emerging concern, priority substances (2008/105/EC) and heavy metals in reclaimed water (R) and in a volcanic aquifer in the NE of Gran Canaria where a golf course has been irrigated with R since 1976 and ii) to relate this presence with physicochemical water properties and hydrogeological media. Reclaimed water and groundwater (GW) were monitoring quarterly from July 2009 to September 2011. Sorption and degradation processes in soil account for more compounds being detected in R. Diazinon and chlorfenvinphos were detected always in R and terbuthylazine, terbutryn and diuron at 90% of frequency. Considering all the samples, the most frequent compounds were chlorpyrifos ethyl, fluorene, phenanthrene and pyrene. Although their concentrations were frequently below 50 ngL-1, some contaminants, were occasionally detected at higher concentrations. Chlorpyrifos ethyl and diuron are priority substances detected frequently and at high concentrations so they must be included in monitoring studies. Geology and location seem to be related to the emerging compounds presence due to occasional contamination events (not related to R irrigation) and therefore not to an existence of a dangerous diffuse contamination level. Thus, it is preferable to select wells with less stable chemical water quality, in order to monitor the risk of emerging compounds presence. Considering the relationship between contaminant presence, chemical water quality, seasonal variation, hydrogeological characteristics and wells location we can conclude that chlorpyrifos ethyl and diuron were the most dangerous priority substances in terms of GW quality so they must be included in all of the monitoring studies, at least in Canary Islands.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The cytotoxicity of dental composites has been attributed to the release of residual monomers from polymerized adhesive systems due to degradation processes or the incomplete polymerization of materials. 2-Hydroxyethyl methacrylate (HEMA) is one of the major components released from dental adhesives. Cytotoxic effects due to high concentrations of HEMA have already been investigated, but the influence of minor toxic concentrations for long-term exposition on specific proteins such as type I collagen and tenascin has not been studied in depth. The objective of this project was to study the effect of minor toxic concentrations of HEMA on human gingival fibroblasts (HGFs) and human pulp fibroblasts (HPFs), investigating modification in cell morphology, cell viability, and the influence on type I collagen and tenascin proteins. Different concentrations of the resin monomer and different times of exposition were tested on both cell lines. The cell vitality was determined by MTT assay, and high-resolution scanning electron microscopy analysis was performed to evaluate differences in cell morphology before and after treatment. To evaluate the variability in the expression and synthesis of procollagen α1 type I and tenascin proteins on HGFs and HPFs treated with HEMA at different concentrations immunofluorescence, RT-PCR and western blot analysis, were carried out. The treatments on HGFs with 3mmol/L HEMA, showed a strong reduction of procollagen α1 type I protein at 72h and 96h, demonstrating that HEMA interferes both with the synthesis of the procollagen α1 type I protein and its mRNA expression. The results obtained on HPFs treated with different concentrations of HEMA ranging from 0,5mmol/L to 3mmol/L and for different exposition times showed a strong reduction in cell viability in specimens treated for 96h and 168h, while immunofluorescence and western blotting analysis demonstrated a reduction of procollagen α1 type I and an overexpression of tenascin protein. In conclusion, our results showed that the concentrations of HEMA we tested, effect the normal cell production and activity, such as the synthesis of some dental extracellular matrix proteins.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The durability of stone building materials is an issue of utmost importance in the field of monument conservation. In order to be able to preserve our built cultural heritage, the thorough knowledge of its constituent materials and the understanding of the processes that affect them are indispensable. The main objective of this research was to evaluate the durability of a special stone type, the crystalline stones, in correlation with their intrinsic characteristics, the petrophysical properties. The crystalline stones are differentiated from the cemented stones on the basis of textural features. Their most important specific property is the usually low, fissure-like porosity. Stone types of significant monumental importance, like the marble or granite belong to this group. The selected materials for this investigation, indeed, are a marble (Macael marble, Spain) and a granite (Silvestre Vilachán granite, Spain). In addition, an andesite (Szob andesite, Hungary) also of significant monumental importance was selected. This way a wide range of crystalline rocks is covered in terms of petrogenesis: stones of metamorphic, magmatic and volcanic origin, which can be of importance in terms of mineralogical, petrological or physical characteristics. After the detailed characterization of the petrophysical properties of the selected stones, their durability was assessed by means of artificial ageing. The applied ageing tests were: the salt crystallization, the frost resistance in pure water and in the presence of soluble salts, the salt mist and the action of SO2 in the presence of humidity. The research aimed at the understanding of the mechanisms of each weathering process and at finding the petrophysical properties most decisive in the degradation of these materials. Among the several weathering mechanisms, the most important ones were found to be the physical stress due to crystallization pressure of both salt and ice, the thermal fatigue due to cyclic temperature changes and the chemical reactions (mostly the acidic attack) between the mineral phases and the external fluids. The properties that fundamentally control the degradation processes, and thus the durability of stones were found to be: the mineralogical and chemical composition; the hydraulic properties especially the water uptake, the permeability and the drying; the void space structure, especially the void size and aperture size distribution and the connectivity of the porous space; and the thermal and mechanical properties. Because of the complexity of the processes and the high number of determining properties, no mechanisms or characteristics could be identified as typical for crystalline stones. The durability or alterability of each stone type must be assessed according to its properties and not according to the textural or petrophysical classification they belong to. Finally, a critical review of standardized methods is presented, based on which an attempt was made for recommendations of the most adequate methodology for the characterization and durability assessment of crystalline stones.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Lo studio dei processi biogeochimici che avvengono all’interfaccia acqua-sedimento riveste grande importanza per comprendere quali fattori ambientali siano responsabili di un eventuale modifica nel bilancio del carbonio organico e di altri elementi maggiori o minori e può` fornire un' indicazione su quali siano le aree più sensibili a tali processi. In questo studio sono stati analizzati i meccanismi che guidano la mineralizzazione della sostanza organica in aree caratterizzate da differenti condizioni idrodinamiche, batimetriche e trofiche nel Mediterraneo centrale. In particolare sono state prelevate carote di sedimento e analizzate le acque interstiziali in siti localizzati nell'Adriatico centro-meridionale, caratterizzati da basse profondità, alti tassi di sedimentazione e elevati apporti di sostanza organica, e in siti localizzati nello Ionio centro-settentrionale, caratterizzati da profondità crescenti, minori tassi di sedimentazione e ridotti apporti fluviali. L'analisi dei processi di degradazione della sostanza organica evidenzia differenze regionali tra il bacino adriatico e quello ionico: processi di mineralizzazione ossica e subossica appaiono intensi nei sedimenti adriatici, diversamente il bacino ionico appare caratterizzato principalmente da processi di degradazione ossica della sostanza organica. Inoltre, relativamente ai flussi bentici di Carbonio Inorganico Disciolto (DIC) flussi inversi sono stati registrati nei due bacini: i sedimenti adriatici si comportano come sourse di DIC, mentre i sedimenti Ionici si comportano come dei sink di DIC suggerendo una possibile precipitazione di carbonati nel bacino ionico.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The last half-century has seen a continuing population and consumption growth, increasing the competition for land, water and energy. The solution can be found in the new sustainability theories, such as the industrial symbiosis and the zero waste objective. Reducing, reusing and recycling are challenges that the whole world have to consider. This is especially important for organic waste, whose reusing gives interesting results in terms of energy release. Before reusing, organic waste needs a deeper characterization. The non-destructive and non-invasive features of both Nuclear Magnetic Resonance (NMR) relaxometry and imaging (MRI) make them optimal candidates to reach such characterization. In this research, NMR techniques demonstrated to be innovative technologies, but an important work on the hardware and software of the NMR LAGIRN laboratory was initially done, creating new experimental procedures to analyse organic waste samples. The first results came from soil-organic matter interactions. Remediated soils properties were described in function of the organic carbon content, proving the importance of limiting the addition of further organic matter to not inhibit soil processes as nutrients transport. Moreover NMR relaxation times and the signal amplitude of a compost sample, over time, showed that the organic matter degradation of compost is a complex process that involves a number of degradation kinetics, as a function of the mix of waste. Local degradation processes were studied with enhanced quantitative relaxation technique that combines NMR and MRI. The development of this research has finally led to the study of waste before it becomes waste. Since a lot of food is lost when it is still edible, new NMR experiments studied the efficiency of conservation and valorisation processes: apple dehydration, meat preservation and bio-oils production. All these results proved the readiness of NMR for quality controls on a huge kind of organic residues and waste.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Volatile amines are prominent indicators of food freshness, as they are produced during many microbiological food degradation processes. Monitoring and indicating the volatile amine concentration within the food package by intelligent packaging solutions might therefore be a simple yet powerful way to control food safety throughout the distribution chain.rnrnIn this context, this work aims to the formation of colourimetric amine sensing surfaces on different substrates, especially transparent PET packaging foil. The colour change of the deposited layers should ideally be discernible by the human eye to facilitate the determination by the end-user. rnrnDifferent tailored zinc(II) and chromium(III) metalloporphyrins have been used as chromophores for the colourimetric detection of volatile amines. A new concept to increase the porphyrins absorbance change upon exposure to amines is introduced. Moreover, the novel porphyrins’ processability during the deposition process is increased by their enhanced solubility in non-polar solvents.rnrnThe porphyrin chromophores have successfully been incorporated into polysiloxane matrices on different substrates via a dielectric barrier discharge enhanced chemical vapour deposition. This process allows the use of nitrogen as a cheap and abundant plasma gas, produces minor amounts of waste and by-products and can be easily introduced into (existing) roll-to-roll production lines. The formed hybrid sensing layers tightly incorporate the porphyrins and moreover form a porous structure to facilitate the amines diffusion to and interaction with the chromophores.rnrnThe work is completed with the thorough analysis of the porphyrins’ amine sensing performance in solution as well as in the hybrid coatings . To reveal the underlying interaction mechanisms, the experimental results are supported by DFT calculations. The deposited layers could be used for the detection of NEt3 concentrations below 10 ppm in the gas phase. Moreover, the coated foils have been tested in preliminary food storage experiments. rnrnThe mechanistic investigations on the interaction of amines with chromium(III) porphyrins revealed a novel pathway to the formation of chromium(IV) oxido porphyrins. This has been used for electrochemical epoxidation reactions with dioxygen as the formal terminal oxidant.rn

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Das Hydroxyl Radikal ist, auf globalem Maßstab, das bedeutendste Oxidant in der Atmosphäre. Es initiiert den Abbauprozess vieler, teilweise schädlicher, Spurengase und insbesondere den von flüchtigen Kohlenwasserstoffen (VOC). Die OH Konzentration ist somit ein gutes Maß für die augenblickliche Selbstreinigungskapazität der Atmosphäre. Messungen zu nächtlicher Zeit mit LIF-FAGE-Instrumenten (engl.: laser-induced fluorescence - fluorescence assay by gas expansion) haben Konzentrationen des Hydroxylradikals (OH) ergeben, die signifikant höher waren, als sich mit der bekannten Chemie erklären ließ. Um herauszufinden, ob ein solches Signal wirklich atmosphärisches OH ist oder von einer störenden Spezies stammt, die im Messinstrument OH produziert, wurde das LIF-FAGE-Instrument des Max-Planck-Instituts für Chemie (MPIC) im Rahmen dieser Doktorarbeit modifiziert und getestet. Dazu wurde ein so genannter Inlet Pre-Injector (IPI) entwickelt, mit dem in regelmäßigen Abständen ein OH-Fänger in die Umgebungsluft abgegeben werden kann, bevor das OH vom Instrument erfasst wird. Mit dieser Technik ist es möglich, ein Hintergrund-OH (OHbg), d. h. ein im Instrument erzeugtes OH-Signal, vom gemessenen OH-Gesamtsignal (OHtot) zu trennen. Die Differenz zwischen OHtot und OHbg ist die atmosphärische OH-Konzentration (OHatm). Vergleichsmessungen mit der hier entwickelten Technik, dem IPI, in zwei verschiedenen Umgebungen mit Instrumenten basierend auf Massenspektrometrie mit chemischer Ionisation (CIMS, engl.: chemical ionization mass spectrometry) als alternativer Methode des OH-Nachweises, zeigten eine weitgehende Übereinstimmung. Eine umfassende Beschreibung des Systems zur Ermittlung der Ursache des OHbg hat ergeben, dass es weder von einem Artefakt des Instruments noch von hinlänglich bekannten und beschriebenen LIF-FAGE-Interferenzen stammt. Zur Bestimmung der Spezies, die das OHbg-Signal verursacht, wurden verschiedene Laborstudien durchgeführt. Die Arbeit im Rahmen dieser Doktorarbeit hat ergeben, dass das LIF-FAGE-Instrument leicht auf OH reagiert, das beim monomolekularen Zerfall stabilisierter Criegee-Intermediate (SCI) im Niederdruckbereich des Instruments gebildet wird. Criegee-Intermediate oder Carbonyloxide entstehen bei der Ozonolyse ungesättigter flüchtiger Kohlenwasserstoffverbindungen (VOC, engl.: volatile organic compounds) und können daher in der Umgebungsluft vorkommen. Anhand von Tests mit verschiedenen Verweilzeiten der SCI im Niederdruckbereich des Instruments in Verbindung mit einem detaillierten Modell mit der neuesten SCI-Chemie wurde die monomolekulare Zerfallsgeschwindigkeit von 20  10 s-1 für den syn-Acetaldehyd-Oxykonformer bestimmt. Der in Feldkampagnen gemessene OHbg-Wert wurde dahingehend untersucht, ob SCI die Quelle des beobachteten Hintergrund-OH im Feld sein könnten. Das Budget für die SCI-Konzentration, das für die Kampagnen HUMPPA-COPEC 2010 und HOPE 2012 berechnet wurde, ergab eine SCI-Konzentration zwischen ca. 103 und 106 Molekülen pro cm3. In der Kampagne HUMPPA-COPEC 2010 ergab die Schwefelsäurekonzentration, dass die OH-Oxidation von SO2 allein die gemessene H2SO4-Konzentration nicht erklären konnte. In dieser Arbeit konnte gezeigt werden, dass das Hintergrund-OH mit dieser ungeklärten Produktionsrate von H2SO4 korreliert und somit die Oxidation von SO2 durch SCI als mögliche Erklärung in Frage kommt. Ferner korreliert das Hintergrund-OH in der Kampagne HOPE 2012 mit dem Produkt aus Ozon und VOC und konnte mit SO2 als SCI Fänger entfernt werden. Qualitativ zeigen wir somit, dass das in der Umgebungsluft gemessene Hintergrund-OH wahrscheinlich durch den monomolekularen Zerfall von SCI verursacht wird, doch sind weitere Studien notwendig, um die quantitativen Beziehung für diese Spezies und dem Hintergrund-OH in unserem Instrument zu bestimmen.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

PURPOSE: This pilot study evaluated the wound healing and tissue response after placement of two different skin substitutes in subgingival mucosal pouches in rabbits. MATERIALS AND METHODS: Four rabbits were selected to receive a commercially available skin substitute consisting of a collagen matrix with fibroblasts and an epithelial layer (test membrane 1) and a prototype device consisting of a collagen matrix with fibroblasts only (test membrane 2). In each rabbit, two horizontal incisions were made in the buccal alveolar mucosa of the maxilla bilaterally to create submucosal pouches. Three pouches in each animal were filled with either the test 1 or test 2 membranes, and one pouch was left without a membrane (sham-operated control). All rabbits were sacrificed after a healing period of 4 weeks, and histologic samples were prepared and examined. RESULTS: After a healing period of 1 month, both tested membranes were still visible in the sections. Test membrane 1 was still bilayered, contained inflammatory cells in its center, and was encapsulated by a thick fibrous tissue. Numerous ectopic calcifications were evident in the collagenous part of the membrane and in association with some basal epithelial cells. Test membrane 2 was also encapsulated in fibrous tissue, with inflammatory cells present only between the fibrous encapsulation and the remnants of the membrane. For test membrane 2, no calcifications were visible. CONCLUSIONS: Test membrane 1 seemed to be more resistant to degradation, but there was also a more pronounced inflammatory reaction in comparison to test membrane 2, especially in the vicinity of the keratinocytes. The significance of the ectopic calcifications, along with that of the resorption or degradation processes of both tested membranes, must be evaluated in future experimental studies, with different time points after implantation examine

Relevância:

60.00% 60.00%

Publicador:

Resumo:

In the Peruvian Andes, a long history of interaction between the local populations and their natural environment has led to extraordinary levels of agrobiodiversity. However, in sharp contrast with this biological wealth, Andean indigenous populations live under most precarious conditions. Moreover, natural resources are undergoing severe degradation processes and local knowledge about biodiversity management is under serious pressure. Against this background, the BioAndes Programme is developing initiatives based on a biocultural approach that aim at fostering biodiversity through the enhancement of cultural processes. On the basis of intercultural dialogue, joint learning and capacity development, and transdisciplinary action-research, indigenous communities, development practitioners, and researchers strive for the creation of innovative ways to contribute to more sustainable economic, socio-cultural, and political valorization of Andean biodiversity. Project activities are diverse and range from the cultivation, transformation, and commercialization of organic Andean fruits in San Marcos, Cajamarca Department, to the recuperation of natural dying techniques for alpaca wool and traditional weaving in Pitumarca, Cusco Department, and the promotion of responsible ecotourism in both regions. Based on the projects’ first two-years of experience, the following lessons learnt will be presented and discussed: 1. The economic valorization and commercialization of local products can be a powerful tool for the revival and innovation of eroded know-how; at the same time it contributes to the strengthening of local identities, in parallel with the empowerment of marginalized groups such as smallholders and women. 2. Such initiatives are only successful when they are embedded within activities that go beyond the focus on local products and seek the valorization of the entire natural and cultural landscape (e.g. through the promotion of agrotourism and local gastronomy, more sustainable management of local resources including the restoration of ecosystems, and the realization of inventories of local agrobiodiversity and the knowledge related to it). 3. The sustainability of these initiatives, which are often externally induced, is conditioned by the ability of local actors to acquire ownership of projects and access to the knowledge required to carry them out, which also means developing the personal and institutional capacities for handling the whole chain from production to commercialization. 4. The confrontation of different economic rationalities and their underlying worldviews that occur when local or indigenous people integrate into the market economy implies the need for a dialogical co-production of knowledge and collective action by local people, experts from NGOs, and political authorities in order to better control the conditions relating to the market economy. The valorization of local agrobiodiversity shows much potential for enhancing natural and cultural diversity in Southern countries, but only when local communities can participate in the shaping of the conditions under which this happens. Such activities should be designed in the mid- to long-term as part of social learning processes that are carefully embedded in the local context. Supporting institutions play a crucial role in these processes, but should see themselves only as facilitators, while ensuring that control and ownership remain with the local actors.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Soil and vegetation are interacting factors controlling erosion. Soil degradation processes may affect the normal tree and shrub development and inversely, vegetation can modulate the velocity and intensity of soil development or denudation. A dendrogeomorphological approach can be used to study these interactions, allowing to obtain a date and estimate mean or specific erosion rates. This is especially useful in an unrecorded badlands and gullied environments, where the scarce vegetation may be the only proxy available to quantify the different geomorphic processes which have occurred. This paper provides a fundamental review of the dendrogeomorphological methodology applied to erosion measurement in badlands. Focusing on the response of the vegetation to the geomorphic processes, this paper: (a) describes the methodology developed to estimate erosion rates with exposed roots; (b) shows new advances through case studies; and finally, (c) discusses future lines of research to reduce methodological uncertainties and for making dendrogeomorphology more widely applicable.