Lietuvoje sparčiai daugėja nykstančių ežerų, kuriuos būtina valyti. Šiuo metu, jų skaičius jau siekia apie tris tūkstančius. Uždumblėję ežerai daro neigiamą poveikį aplinkai, nyksta ir nebeatlieka savo paskirties. Siekiant sustabdyti ežerų nykimo procesą, didžiausias dėmesys yra skiriamas ežerų valymo būdui naudojant žemsiurbes. Šis valymo būdas yra gana populiarus nors ir brangus. Tačiau ne visos žemsiurbės pritaikytos Lietuvos ežerams valyti. Pagrindinė darbo problema – dumblėjančių Lietuvos ežerų atgaivinimas panaudojant žemsiurbes. Darbo tikslas – įvertinti Lietuvoje naudojamų žemsiurbių tinkamumą ežerams valyti. Darbo uždaviniai: 1. įvertinti gaminamų žemsiurbių tinkamumą Lietuvos ežerų valymui; 2. išanalizuoti šalyje naudojamų žemsiurbių eksploatacinį našumą, pulpos konsistenciją ir transportavimo atstumą; 3. įvertinti iškasamo dumblo tolygumą, valant ežerus; 4. įvertinti Lietuvoje naudojamų žemsiurbių tinkamumą ežerų valymui. Darbo struktūra. Darbą sudaro: įvadas, 3 skyriai, išvados, literatūros sąrašas ir priedai. Darbe pateikti 38 paveikslai, 1 lentelė, 4 priedai. Pirmoje darbo dalyje nagrinėjamas pasirinktos temos aktualumas atliekant literatūros analizę. Antroje darbo dalyje pateikiama tyrimų metodika. Trečioje darbo dalyje pateikiami atlikto tyrimo rezultatai. Darbe aprašomi atlikti trijų Vainiekio, Paežerėlių ir Talkšos ežerų, valytų 2002, 2006, 2007 ir 2008 metais, bei juose naudotų žemsiurbių VT – 2, „Watermaster Classic III“, „Christa Wendland” gauti... [toliau žr. visą tekstą] / The extinction of the lakes, that should be inevitably cleaned, is in great progress in Lithuania. There are about three thousand such kind of lakes. The siltified lakes have the negative influence on the natural environment, they are nearly to extinction and do not serve the purpose. In order to stop the process of the absolute extinction of the lakes, the great attention is paid to the means and methods for cleaning the lakes by using the special machines called suction dredges that are popular, nevertheless, quite expensive. Though, not all kinds of dredges produced are suitable for cleaning the lakes of Lithuania. The main problem of the work- the revival of the siltified lakes by using the suction dredges. The aim of the work - to evaluate the usability of dredges for cleaning the lakes of Lithuania. The objectives of the work: 1. Evaluate the usability of dredges that are produced, for the cleaning of the lakes of Lithuania. 2. Analyze the efficiency of exploitation of the dredges used in Lithuania, the consistence of the solid silt and the distance of transportation of the pulp. 3. Evaluate the even distribution of the silt that is removed. 4. Evaluate the usability of the suction dredges that are exploited in Lithuania. The structure of the work. The parts of the final work are: introduction, 3 sections, conclusions, recommendations, list of literature sources and appendixes. There are 38 pictures, 1 table, 4 appendixes in the final work. In the first part of the... [to full text]

Magistriniame darbe pateikta literatūros analizė, tyrimų tikslas ir uždaviniai, tyrimo metodika, tyrimų rezultatai ir jų analizė, išvados. Nustatyta, kad Lietuvoje ežerams valyti naudojamų žemsiurbių pagrindinis trūkumas yra siurbiama skysta pulpa ir mažas jos transportavimo atstumas. Tyrimų tikslas yra įvertinti dažniausiai naudojamos žemsiurbės „Watermaster Classic III“ tinkamumą ežerų valymui Lietuvoje. Tiesioginiais matavimais, trijuose pjūviuose, buvo nustatyti vandens gyliai išvalytose Masčio ežero ir Pakruojo tvenkinio dalyse. Suspenduotų dalelių kiekiui vandenyje nustatyti, iš Masčio ežero buvo paimti buteliu – batometru vandens mėginiai (iš karto baigus siurbimą), tūriniu būdu išmatuotas žemsiurbės našumas. Išmatavus vandens gylius, buvo atlikta aprašomoji stastika, kurios metu buvo pasitelkta „Hydrotech” bei “Microsoft Excel”programinė įranga. Autorius savo jėgomis atliko visus tyrimus. Nustatyta, kad valant Masčio ežero dalį žemsiurbe „Watermaster Classic III“, valymo tolygumas atskiruose pjūviuose siekė 8,1–10,2 %, žymiai prastesnis nei palyginimui Pakruojo tvenkinio dalyje, valant žemsiurbe „3350MK“ (tolygumas sieke 2,9–3,2 %). Esant darbinei konsistencijai 3,7 %, žemsiurbės „Watermaster Classic III“ našumas už 433 m siekė 76 %. Suspenduotų dalelių kiekis tik pirmą dieną prie žemsiurbės buvo žymiai didesnis už foninį lygį, už 10–20 m foninio lygio, o vėliau visur tapo foninio lygmens. Žemsiurbės „Watermaster Classic III“ dienos darbo laiko panaudojimo... [toliau žr. visą tekstą] / This Master's thesis presents the analysis of the literature, the aim and tasks of researches, the methodology, results, analysis and conclusions of the research. It was found that the main drawbacks of dredges which are cleaning lakes in Lithuania are the liquid pulp pumped and its low transportation distance. The aim of this research is to evaluate the most commonly used dredges’ “Watermaster Classic III” suitability for cleaning lakes in Lithuania. The water depths in three sections cleaned in Mastis and Pakruojis lakes were determined by direct measurements, to identify the quantity of suspended particles in the water in Mastis lake (immediately after dredging) water samples were taken with bottle – bathometer and the efficiency of dredge was evaluated using volumetric method. After measuring water death the descriptive statistic was carried out using “Hydrotech“ and “Microsoft Excel” software. All researches were made by author itself. It was found that dredging part of the lake Mastis with “Watermaster Classic III” cleaning uniformity in separate sections was 8.1 to 10.2% while cleaning the part of lake Pakruojis with the dredge „3350MK“ uniformity was significantly lower (2,9 to 3,2 %). In 3.7 % operating consistency “Watermaster Classic III” performance at 433 m was 76 %. The quantity of suspended particles only the first day around the dredge was significantly higher than the background level – 10-20 m above it but later everywhere became equal to background level... [to full text]

No description available.

Seagrass habitats in South Florida are exceptionally valuable. They play an important ecological role in the coastal environment by stabilizing sediment, providing habitat for other species and supporting a whole food web. The availability of light and nutrients in aquatic ecosystems are the driving factors behind seagrass distribution. Water quality has been known to influence the abundance, distribution and composition of seagrass beds. South Florida has extensive diverse coastal communities. Throughout its human development dramatic changes have occurred in its natural ecosystems. In South Florida, many examples of seagrass habitat loss are documented, with a variety of contributing factors. The present research investigates the spatial and temporal patterns in benthic vegetation of the North Biscayne Bay marine basin, located just south of the heavily urbanized Port of Miami. The area has been altered significantly through dredging projects to widen and deepen the channels around the port facilities in order to accommodate larger vessels. This study focuses primarily on environmental and physical conditions that are likely to alter the distribution of seagrass. The availability of light and nutrients in aquatic ecosystems are the driving factors behind seagrass distribution and therefore one may expect seagrass degradation if any drastic changes occurred in these parameters. Project data used were collected from the South Florida Fish and Invertebrate Assessment Network project (FIAN), an element of the greater Everglades Restoration Program. Additional Environmental and physical data were obtained from the South Florida Water Management District (SFWMD) and the National Ocean and Atmospheric Administration (NOAA). The FIAN Port of Miami (POM) study location is dominated by three species of seagrass: Thalassia testudinum, Syringodium filiforme, and Halodule wrightii. Analysis has shown that over the seven-year period, 2005 - 2011 the state of the seagrass has been fairly stable with minor perturbances (p > 0.05). There are some seasonal fluctuations evident in seagrass cover-densities, but minimal change was observed between the spring and fall (p > 0.05). Syringodium is the dominant species, followed by Thalassia and Halodule within the POM. Environmental and physical conditions from FIAN (salinity, temperature, sediment depth, turbidity, etc.) varied between years and seasons; however, most measurements remained in the ideal range for seagrass growth. Water depth, sediment depth, and turbidity were significant predictors of seagrass occurrence in the POM; however, water depth was the only major predictor of seagrass cover-density. The available environmental and physical data from the SFWMD showed minimal changes in the environmental and physical measurements across available sample years and are in the ideal range for seagrass. Turbidity has improved since the completion of the port construction and major weather disturbances (hurricanes) in 2005. Minimal changes were detected during the seven year study period (2005-2011) within the seagrass habitat of the heavily urbanized region of POM.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Oceanografia Física, Química e Geológica, Instituto de Oceanografia, 2006. / Submitted by Cristiane Silva (cristiane_gomides@hotmail.com) on 2013-02-18T11:35:13Z No. of bitstreams: 1 2006_Lice.pdf: 2445894 bytes, checksum: 98bb19b4f2e28361a620662224bad0d2 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-11T22:11:39Z (GMT) No. of bitstreams: 1 2006_Lice.pdf: 2445894 bytes, checksum: 98bb19b4f2e28361a620662224bad0d2 (MD5) / Made available in DSpace on 2013-06-11T22:11:39Z (GMT). No. of bitstreams: 1 2006_Lice.pdf: 2445894 bytes, checksum: 98bb19b4f2e28361a620662224bad0d2 (MD5) Previous issue date: 2006 / Os hidrocarbonetos derivados do petróleo são causa de grande preocupação ambiental devido à elevada toxicidade para os seres vivos, especialmente de algumas espécies aromáticas, sendo até mesmo classificadas como carcinogênicas e mutagênicas. A presente pesquisa estudou a capacidade de liberação destes compostos para a coluna de água a partir de sedimentos provenientes de cinco locais suscetíveis a impactos por hidrocarbonetos e potencialmente contaminados da área portuário-estuarina da cidade do Rio Grande, RS, Brasil. A liberação dos hidrocarbonetos foi simulada em testes de elutriação e submetida a diferentes tempos de repouso, 60, 90 e 120 min, a fim de determinar o tempo de residência destas substâncias na coluna de água após um evento crítico de ressuspensão. As análises dos hidrocarbonetos foram realizadas por cromatografia gasosa, acoplada a um detector de ionização por chama para identificação dos hidrocarbonetos alifáticos e a um detector de massa para os hidrocarbonetos policíclicos aromáticos (HPAs). Os mesmos índices geoquímicos indicativos da origem da contaminação nos sedimentos foram utilizados para descrever os hidrocarbonetos liberados dos sedimentos para os elutriatos. O procedimento de normalização dos teores de hidrocarbonetos pela quantidade de sedimento da elutriação aparece como uma importante ferramenta para qualificar a análise da liberação destes compostos. O estudo constatou que os sedimentos contaminados, durante eventos de ressuspensão, agem como fonte de contaminação por hidrocarbonetos alifáticos e por HPAs para a coluna de água. Para os compostos alifáticos não foi verificada influência das características texturais dos sedimentos sobre o tempo de residência na coluna de água. Em geral, o tempo de residência médio determinado foi de 89 horas. O impacto decorrente de uma dragagem analisado através de um modelo empírico é interpretado como leve, uma vez que as quantidadesliberadas são similares a pequenos derrames habitualmente verificados naregião. Uma alta capacidade de liberação e de re-aprisionamento aos sedimentos foi identificada para os n-alcanos ímpares C29, C33 e C17. Os HPAs identificados em quase todos os elutriatos foram o antraceno, naftaleno e fenantreno. Foi caracterizada uma contaminação pontual no Posto Náutico. Se neste local viesse a ocorrer uma dragagem, de acordo com o modelo empírico, os compostos benzo(a)antraceno e criseno ultrapassariam os limites do CONAMA e WQC, enquanto o benzo(b)fluoranteno, benzo(k)fluoranteno e benzo(a)pireno ultrapassariam o WQC. Salienta-se que os dados apresentados podem estar subestimados de acordo com o modelo empírico utilizado e as limitações metodológicas do presente estudo. / The petroleum derivate hydrocarbons are cause of great environmental concern due to its raised toxicity to living beings, especially from some aromatic ones, being even classified as carcinogenic and mutagenic. The present research studied the release capacity of these compounds to the water column from the sediments coming from five hydrocarbons impacts susceptible places potentially contaminated in estuarine harbor area of Rio Grande City, RS, Brazil. The hydrocarbons release was simulated by elutriation tests and submitted to different rest times, 60, 90 and 120 min, in order to determine the residence time of these substances on the water column after a critic ressuspention event. The hydrocarbons analyses had been carried out by gaseous chromatography, connected to a flame ionization detector for identification of aliphatic hydrocarbons and connected to a mass detector for polycyclic aromatic ones (PAHs). The same geochemical index used for sediments as indicative of contamination origin had been used to describe the hydrocarbons released to elutriate from sediments. The procedure hydrocarbon content normalization for the sediment amount on elutriation appears as an important tool to qualify the release analysis of these compounds. The study evidenced that contaminated sediments, during ressuspention events, acts as a source of contamination to the water column by aliphatic hydrocarbons and PAHs. To the aliphatic composites was not verified an influence of sediments texture characteristics on water column residence time. In general, 89 hours was determined as mean residence time. The dredge impact was analyzed by an empiric model and is interpreted as weak therefore the released quantities are similar to small spills usually verified on the region. A high release and recapture sediment capacity was identified to the odd nalkanes C29, C33 and C17. In almost all elutriates was identified the HPAs anthracene, naphthalene and phenanthrene. A punctual contamination was characterized in Posto Náutico (nautic oil station). If on this site occurs a dredge work, due to de empiric model, the composites benzo(a)anthracene and chrysene will exceed the CONAMA and WQC limits while benzo(b)fluoranthene, benzo(k) fluoranthene and benzo(a)pyrene will exceed the WQC limits. The shown data can be sub estimated in agreement with the present study empiric model used and methodological limitations.

Les étoiles de la branche asymptotique (AGBS) sont surtout connues pour deux faits historiques: - le "mystère des éléments s": riches en neutrons et possédant une durée de vie inférieure à celle des AGBS, ces éléments sont néanmoins présents dans les enveloppes de ces étoiles. De plus, les abondances de ces éléments "s" sont mal reproduites par les modèles existants. - le "mystère des étoiles carbonées": ces étoiles, dont les abondances vérifient C/O>1, sont majoritairement de faible luminosité. C'est un drainage (DUP) qui permet aux AGBS de devenir carbonées: l'enveloppe convective (CE) descend là où brûle 1H et prélève du Carbone, produit plus bas par la combustion de 4He et amené là par des languettes convectives récurrentes, les pulses thermiques. Or, les profondeurs des DUP modélisés pour des AGBS de faibles masses n'expliquent la forte proportion de Carbone observée. Ces deux mystères conduisent à identifier deux paramètres majeurs de l'évolution des abondances: la perte de masse et le DUP. Le premier contrôle la fin de la phase AGB et la température à la base de la CE, à masse stellaire fixée. Le deuxième maîtrise l'apport de protons entre les couches de 1H et de 4He et la modification des abondances de surface. Et c'est de la physique non standard qui est sous-jacente à ces paramètres: couplage gaz-poussière, pulsations, ondes de chocs, dégénérescence, convection avec gradient de composition, mélange non standard (non thermiquement induit)... Plusieurs études ayant été faites, tant sur les mécanismes de production que sur le paramétrage de la perte de masse, ce travail est centré sur l'influence du traitement du DUP sur la nucléosynthèse des AGBS de masses intermédiaires. La nucléosynthèse étant connue grâce à une coopération étroite entre méthodes observationnelles et théoriques, cette thèse a été menée sur les deux fronts. Cela rend possible "l'éclairage" de chacune des méthodes par les forces et les faiblesses de l'autre et donc de mieux évaluer la fiabilité d'une mesure réalisée sur Terre lorsqu'on veut l'interpréter en terme d'abondances au centre de l'étoile. La partie observationnelle de ce travail est focalisée sur l'amélioration de la précision de rapports isotopiques délicats à interpréter dans des enveloppes particulières: rapports d'éléments lourds de sources brillantes ou rapports des CNO dans des sources présentant des anomalies d'abondances. L'interprétation des observations a requis deux modélisations avancées dont l'une, faisant partie intégrante de cette thèse, porte sur l'émission de l'enveloppe, et l'autre, portant sur le processus "s", a fait l'objet d'une collaboration. Dans le domaine théorique, le code d'évolution stellaire de Grenoble a été optimisé pour les AGBS afin d'étudier l'influence de la modélisation physique et du traitement numérique du DUP sur la nucléosynthèse. Le cœur de la modélisation d'une étoile, l'équation d'état (EOS), a été réécrite et une grande partie du traitement numérique du code a été revue. La physique du mélange non standard a été incorporée et "l'arsenal" numérique nécessaire à la mise en œuvre de cette physique a fait l'objet d'une collaboration. Ce travail a permis la précision des caractéristiques d'enveloppes d'étoiles J (riches en 13C), la détermination de 35Cl / 37Cl dans IRC+10216 et la production d'outils de calcul performants pour les étoiles (même de faibles masses) et leurs enveloppes moléculaires. Mais il a surtout montré que l'incorporation de mélange non standard permet à la fois d'augmenter la profondeur du DUP et de produire une poche de 13C propice au processus "s". Ce fait, ajouté aux difficultés pour concilier les résultats d'observations des étoiles J avec les modèles, tend à réorienter le futur des modèles d'AGBS. Il faudrait disposer de modèle d'AGBS plus généraux, notamment pour les faibles masses, cohérents avec la physique et le numérique de la phase évolutive qui les précède, elle qui est naturellement modélisée avec du mélange non standard. En prime, les changements effectués dans le code et notamment l'élaboration d'une nouvelle EOS, ont permis de modéliser le flash de l'Helium et de produire des tracés d'étoiles pré séquence principale (PMS) jusqu'à 0.1 masse solaire concurrençant les codes les plus spécialisés.

The aim of this thesis is to consider the operation of dredge pump and design new technology of slag removal including return on investment calculation. The operation optimization itself was preceded by analysis of present technology, data collection, calculation of pressure losses and pinpointing the causes of their origin. Subsequently, the measures to elimination of losses were deduced and these measures were implemented into optimization of dredge pump operation itself. The return on investment into the new technology of slag removal is calculated in the last chapter, considering its feasibility in the heating plant.

No description available.

The state of Georgia has two large ports that are accessed by way of navigable entrance channels. One of these ports is located in Brunswick, Georgia, and is maintained by the United States Army Corps of Engineers via periodic dredging. Sediments removed from the channel are typically pumped several miles offshore of Brunswick and placed in dredged material mounds, thus removing the sediment from the littoral cycle. This offshore placement, while being the most economically viable method, often negatively impacts the sediment budget of the coastal region and causes erosion downdrift of the channel, specifically along Jekyll Island. Onshore placement of the dredged material is not feasible due to increased associated costs and the high fraction of fines present in the material; thus, nearshore placement is a potentially viable alternative. Nearshore placement could possibly reduce erosion rates and provide protection to property from waves and storms. The USACE initiated a thorough field data collection campaign in 2002 to study the possibility of beneficial placement of dredged material. The author analyzed the existing data to predict the rate and direction of sediment movement away from an existing dredge mound. These predictions are then compared to bathymetric survey data in an effort to validate the results and methodologies used for sediment transport predictions. The ultimate goal is to use the results of this study along with numerical models currently being developed by the Corps to assess the possibility of sediments being transported toward the shore thus re-entering the littoral cycle and providing a benefit to the coast of Georgia.

No description available.