• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 175
  • 41
  • 22
  • 16
  • 16
  • 16
  • 16
  • 16
  • 16
  • 13
  • 10
  • 8
  • 6
  • 3
  • 2
  • Tagged with
  • 370
  • 44
  • 41
  • 41
  • 38
  • 36
  • 36
  • 30
  • 28
  • 26
  • 25
  • 22
  • 19
  • 19
  • 18
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
351

Utilization of electrocoagulation for water and wastewater treatment and nutrient recovery:techno-economic studies

Kuokkanen, V. (Ville) 16 February 2016 (has links)
Abstract Electrocoagulation (EC) is an emerging technology that combines the functions and advantages of conventional coagulation, flotation, and electrochemistry in water and wastewater treatment. The aims of this work included doing an updated literary review of recent feasible applications of EC, which were found to be plentiful. Since the economic and practical operational key figures related to EC haven’t been extensively mapped out before, this was a prime objective of this part of the work. The aim of the next part of this work was to find new feasible applications for EC in the treatment of water and wastewater. The studied wastewaters included bio- and synthetic oil-in-water emulsions, various industrial nutrient-containing wastewaters, and peat bog drainage water containing humic substances (an interesting and topical problem, especially in Finland). These studies proved the feasibility of EC. In addition, larger-scale experiments were also conducted successfully, thus proving the scalability of the EC process. Extensive economic analyses of the studied EC applications were also done. The operational costs and energy consumption of EC were found to be very low—typically about 0.1–1.0 €/m3 and 0.4–4.0 kWh/m3. It has been forecasted that in the future there will be a shortage of virgin phosphorus. Therefore, another essential purpose of this work was to conduct a preliminary study on the feasibility of using EC for nutrient (especially phosphorus, but also nitrogen) removal and recovery from different types of real wastewater. Specifically, it may be possible to use EC sludges containing notable amounts of phosphorus and nitrogen as additives in granulated bio ash-based fertilizer products for various applications. This is a novel idea and a “hot topic” in the waste utilization sector and in circular and bioeconomy. / Tiivistelmä Elektrokoagulaatio (electrocoagulation, EC) on nosteessa oleva teknologia, joka yhdistää perinteisen koagulaation, flotaation ja sähkökemian hyödyt ja mahdollisuudet vesien ja jätevesien käsittelyssä. Tämän työn ensimmäisenä tavoitteena oli laatia kirjallisuuskatsaus EC:n viimeaikaisista käyttökelpoisista sovelluksista, joita löytyi runsaasti. Koska EC:n toiminnallisia ja taloudellisia avainlukuja ei ole kartoitettu kattavasti aiemmin, tämän tekeminen oli tämän osion tärkein tavoite. Väitöstyön seuraavana tavoitteena oli löytää uusia sovellutuksia EC:lle vesien ja jätevesien käsittelyssä. Tutkittuja vesiä olivat bio- ja synteettisistä öljyistä valmistetut öljy-vesiemulsiot, erilaiset teolliset ravinnepitoiset jätevedet ja humusainepitoiset turvesoiden valumavedet (kiinnostava ja ajankohtainen ongelma, erityisesti Suomessa). EC todettiin käyttökelpoiseksi teknologiaksi näissä kokeissa. Suuremman skaalan kokeilla todistettiin lisäksi EC-prosessin skaalautuvuus. Lisäksi, em. EC-sovellutuksista suoritettiin kattavat taloudelliset analyysit. EC:n käyttökustannukset ja energiankulutus todettiin erittäin pieniksi, tyypillisesti ne olivat välillä 0.1–1.0 €/m3 ja 0.4–4.0 kWh/m3. On ennustettu, että tulevaisuudessa on pulaa neitseellisestä fosforista. Tästä johtuen eräs tämän työn keskeisistä tarkoituksista oli suorittaa alustavia kokeita liittyen EC:n käyttökelpoisuuteen ravinteiden (erityisesti fosfori, mutta myös typpi) poistossa ja talteenotossa aidoista jätevesistä. Erityisesti jatkossa voisi olla järkevää hyödyntää runsaasti fosforia ja typpeä sisältäviä EC-sakkoja lisäaineina rakeistetuissa biotuhkapohjaisissa lannoitteissa eri sovellutuksissa. Tämä idea on uusi ja on jo herättänyt suurta kiinnostusta mm. kierto- ja biotaloussektoreilla.
352

Vegetation history and human-environment interactions through the late Holocene in Konar Sandal, Kerman, SE Iran

Gurjazkaite, Karolina January 2017 (has links)
The Jiroft valley, in southeastern Iran, was an important agricultural centre since the Early Bronze Age (3rd millennium BCE). The valley is characterized by harsh environmental settings: hot climate with poor rainfall. However, more optimal conditions may have prevailed earlier that supported ancient settlements. A 250-cm sediment core was retrieved from a peat-land at Konar Sandal, a major archaeological find attributed to Jiroft culture. The palynological data from this core was combined with geochemical and sedimentological proxies aimed at establishing the human-environment interactions in the area. The study focus was directed at vegetation history and landscape evolution, hydroclimatic changes and past human activities, that started just after the projected collapse of the Jiroft (4 ka) and extended all the way from the late Bronze Age to the Mongol invasion (0.6 ka). The results indicate that the valley was dominated by Saharo-Sindian open pseudo-savannah vegetation for the last 4000 years. However, due to anthropogenic clearance and intensified agro-pastoral activities, and also climatic factors, the land cover shifted from open xeric scrubland forests to more open, degraded landscapes. The principal human practice in these early settlements was cereal cultivation. But it is likely that during the more arid periods, communities retreated and abandoned agriculture, facilitating successional processes. Such droughts occurred in 4-3.8 ka and 3.4-2.8 ka and were supported by palynological data, C/N and Fe2O3 content. Peat formation was characteristic to the wetland during these arid periods. These droughts corresponded to drought phases detected in other studies, and were attributed to changes in Siberian Anticyclones. Dynamics of Artemisia and desert shrubs indicate milder climate around 3.8-3.4 ka and 2.8-0.6 ka. In the latter episode, during the rule of Persian Empire (ca. 550 BCE-650 CE) and Islamic epoch, the highest vegetation degradation state and most intensive human activities were observed. Some inconspicuous human practices, such as date cultivation, may have occurred on site as an adaptation to extreme environmental conditions. / High-resolution paleolimnological records from Lake Jazmurian: Climate-culture evolution at Jiroft in southeast Iran during the Holocene
353

Physicochemical studies regarding the utilization of wood- and peat-based fly ash

Pesonen, J. (Janne) 11 October 2016 (has links)
Abstract The main aim of the European Union’s waste legislation and the corresponding Finnish waste legislation is to reduce the production of waste. Further, the aims of the European Union’s growth strategy are to reduce the production of greenhouse gases, increase the use of renewable energy, and improve energy efficiency. According to the renewed Waste Tax Act, a waste tax has to be paid on all fly ashes that are deposited in landfills in Finland. A large amount of wood- and peat-based fly ashes are formed annually in Finland, and the amount is likely to increase in the future due to the increasing use of renewable energy. Previously, these ashes have mainly been deposited in industrial landfills, but the need to utilize the fly ashes has increased recently due to changes in waste legislation. In this thesis, several issues related to the utilization of wood- and peat-based fly ash were studied, with the general objective of improving the utilization potential of such ashes. As the first stage of this research, the suitability of willow ash for use as a fertilizer was studied. Willow ash would be well suited for use as a fertilizer due to its very high nutrient content. However, cadmium, a heavy metal, was found to be enriched in the ashes of the studied willow species. Due to this, special attention should be paid when choosing willow species for energy production. In the second stage of the research, the possibility of improving the strength development of wood- and peat-based fly ashes, as well as the possibility of stabilizing fly ash containing high amounts of heavy metals via the addition of cement and/or alkali activation, was investigated. Strength development was found to be dependent on the amount of reactive calcium and the ratio between that amount of reactive calcium and the sum of the reactive silicon, aluminum, and sulfur (Ca/(Si + Al + S)). The studied methods performed well in terms of stabilizing barium, copper, lead, and zinc. During the next stage, the effect of different chemical digestion methods, which are regulated by the Finnish waste legislation, on the utilization potential of fly ash was studied. The digestion method had a significant impact on the results of the potassium content analysis, which could affect the possibility of using fly ash as a fertilizer. As the final stage of the research, the co-granulation of ash with sewage sludge and lime was studied. From a technical point of view, the co-granulation was successful, although the compressive strength of the granules was low. Additionally, an insufficient nitrogen content was achieved with a sludge addition of 20-40 weight%. / Tiivistelmä Euroopan unionin jätelainsäädännön ja sitä vastaavan suomalaisen lainsäädännön tavoitteena on ehkäistä jätteiden muodostumista. Euroopan Unionin kasvustrategian tavoitteena on vähentää kasvihuonekaasupäästöjä, lisätä uusiutuvan energian käyttöä ja parantaa energiatehokkuutta. Uudistetun jäteverolain mukaan kaikista kaato-paikoille sijoitetuista lentotuhkista tulee Suomessa maksaa jäteveroa. Suomessa puu- ja turveperäisiä lentotuhkia muodostuu vuosittain suuria määriä ja määrä tulee vielä kasvamaan uusiutuvan energiankäytön lisääntyessä. Aiemmin nämä tuhkat ovat päätyneet pääasiassa läjitykseen teollisuuden kaatopaikoille, mutta muuttuneen jätelainsäädännön seurauksena tarve hyödyntää lentotuhkia on lisääntynyt. Tässä väitöstyössä tutkittiin puu- ja turveperäisten tuhkien hyödyntämiseen liittyviä kysymyksiä. Työn yleistavoitteena oli parantaa tuhkien hyödyntämis-mahdollisuuksia. Tutkimuksen ensimmäisessä vaiheessa tutkittiin pajutuhkan soveltuvuutta lannoitteeksi. Pajutuhka soveltuisi hyvin lannoitteeksi erittäin hyvien ravinne-pitoisuuksien ansiosta. Raskasmetalleista kadmiumin havaittiin kuitenkin rikastuvan tutkittujen pajulajien tuhkiin. Tähän tulisi kiinnittää erityishuomiota, kun pajulajeja valitaan energiantuotantoa varten. Tutkimuksen toisessa vaiheessa selvitettiin mahdollisuutta parantaa turpeen ja puun lentotuhkien lujittumista sekä raskasmetallipitoisen lentotuhkan stabiloimista sementtilisäyksen ja/tai alkaliaktivoinnin avulla. Lujuuden kehitys riippui reaktiivisen kalsiumin määrästä sekä reaktiivisen kalsiumin määrän ja reaktiivisten piin, alumiinin ja rikin määrien summan välisestä suhteesta (Ca/(Si + Al + S)). Tutkitut menetelmät toimivat hyvin bariumin, kuparin, lyijyn ja sinkin stabiloinnissa. Seuraavassa vaiheessa selvitettiin Suomen lainsäädännössä määritettyjen kemiallisten hajotusmenetelmien vaikutusta tuhkan hyödyntämispotentiaaliin. Hajotusmenetelmällä oli suuri merkitys kaliumin pitoisuutta määritettäessä, mikä voi vaikuttaa lentotuhkan hyödynnettävyyteen lannoitteena. Viimeisessä vaiheessa tutkittiin tuhkan yhteisrakeistusta lietteen ja kalkin kanssa. Teknisesti yhteisrakeistus onnistui hyvin, mutta rakeiden puristuslujuus oli alhainen. Lisäksi 20 - 40 paino% lietelisäyksellä ei rakeisiin saatu riittävän korkeaa typpipitoisuutta.
354

Syncretisms for wind quintet and percussion: A study in combining organizational principles from Southeast Asian music with western stylistic elements.

Seymour, John 05 1900 (has links)
Syncretisms is an original composition scored for flute, oboe, clarinet, horn, bassoon, and marimba (2-mallet minimum, 4 recommended) with an optional percussion part requiring glockenspiel and chimes, and has an approximate duration of 6 min. 45. sec. The composition combines modern western tuning, timbre, and harmonic language with organizational principles identified in music from Southeast Asia (including music from cultures found in Thailand, Cambodia, Malaysia, and Indonesia). The accompanying paper describes each of these organizational principles, drawing on the work of scholars who have performed fieldwork, and describes the way in which each principle was employed in Syncretisms. The conclusion speculates on a method for comparing musical organizational systems cross-culturally.
355

Geovisualization of boreal peatland architecture in a three dimensional hydrogeological framework using ground penetrating radar and LiDAR at Mariana Lakes, Alberta, Canada

Shulba, William Paul 07 June 2021 (has links)
Communicating science in three-dimensional (3D) multimedia is an immersive and interactive way to explore scientific processes (Signals and Communication Technology, 2019). Geovisualization is an emerging 3D multimedia method for visual analysis, synthesis, and presentation of geospatial, geologic, and geophysical data (MacEachren & Kraak, 2001). There is an identified need to develop scientific communication tools to further understand boreal peatland evolution, hydrogeology, ecology, and geochemistry (Bubier et al., 2003) since the International Union of Conservation of Nature asserts that peatlands are among the most valuable ecosystems on Earth, critical for preserving global biodiversity, providing drinking water, minimising flood risk, preventing wildfire, and mitigating climate change (Hama et al., 2000). The intention of this thesis is to communicate a novel approach to geovisualize boreal peatland architecture using Light Detection and Ranging (LiDAR) and Ground Penetrating Radar (GPR). GPR and LiDAR have been used to create 3D subsurface geovisualizations for archaeology (Kenady et al., 2018; Schultz & Martin, 2011) and resource geology (Corradini et al., 2020; Koyan & Tronicke, 2020) although application to peatland hydrogeology is uncommon. Point-source hydrogeological and geochemical data were integrated with 3D geological models to estimate carbon and nitrogen storage in an archetypal boreal peatland near Mariana Lakes, Alberta. Peatland geometry resembled a shallow lake basin with depths greatest in fens (>10 m) and thinnest in bogs (<2 m). Hydraulic conductivity was only a few meters per year and vertical groundwater movement was limited. Sequestered carbon and nutrients increased with depth. The average concentration of dissolved ammonium was 3 grams per cubic metre of peat (g/m3), 5g/m3of Total Kjeldahl Nitrogen, 60g/m3 of dissolved organic carbon and 200g/m3 of dissolved inorganic carbon. Tritium detection from atmospheric atomic weapons radionuclide fallout revealed that in deeper anaerobic peat (catotelm), tritium was absent, signifying groundwater was older than 50 years and not mixed with meteoric waters. Fen catotelm channels are likely acting as gravity-driven hydraulic traps (Tóth, 1999). / Graduate
356

Hydrologická funkce horských vrchovišť a vlastnosti rašelinných vod v pramenné oblasti Vydry / Hydrological function of peat bogs and peat water properties of the Vydra River headwaters

Doležal, Tomáš January 2020 (has links)
The retention potential of landscapes, along with the water regime of spring areas, are important hydrological topics of research, particularly in the current context of increasing extreme drought frequencies. The present work is focused on monitoring the mountain peat bogs, which, due to their overall frequency of occurrence in the spring area of the Vydra river, represent a significant constituent of the rainfall-runoff process of the area of interest. The specific hydropedological features of the organogenous soils (Histosol type soil) provide the high retention potential of the area, however, the influence of these soils on the runoff process is determined by complex physicogeographical factors. The general opinion on the hydrological function of the peat bogs has changed in recent years and the most important factor in the runoff formation in the mountain area of the Šumava Mts. is now thought to be the actual saturation of the headwater, which is predominantly composed of hydromorphic and organogenous soils. The organogenous soils are significant water reservoirs and have an important impact on the landscape. However, they may also intensify the extreme values of the watercourses during extreme precipitation events. The fundamental part of this work focuses on detailed observations of the...
357

Změny koncentrací organického uhlíku v povrchových vodách v pramenných oblastech / Changes of organic carbon in surface waters in headwater areas

Špringerová, Pavla January 2019 (has links)
Diploma thesis is focused on changes of organic carbon (OC) in surface waters in headwater areas. Thesis is in its theoretical part focused on the literature study of currently published research results of the issue. The important part is finding the possible causes of OC variability, especially landcover and soil environment. The practical part is devoted to research in experimental basins of KFGG, namely in the upper Vydra, Blanice and Rolava. The aim of this work is to clarify the relationships between organic matter concentrations and discharge rates regarding to hydrological extremes. Furthermore, the influence of river basin size and various landcover and variability of concentrations and relationship with other indicators of biogeochemism is studied. The relationship between OC and discharge rate is positive and in most river basins strong or very strong. The weakest relationship was monitored on the profiles with the highest proportion of peatlands in the river basin. In these catchments, the highest average concentrations of OC were determined in autumn, in catchments with the lower proportion of peatlands it is in summer. Analysis of rainfall-runoff events confirmed the positive relationship of OC and discharge. The lag time of the maximum OC concentration beyond the maximum discharge...
358

Conditions de l'accumulation du carbone dans une tourbière du Québec méridional : l'influence des facteurs autogènes et des contrôles allogènes

Muller, Serge D. 09 1900 (has links)
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal. / Thèse de doctorat effectuée en cotutelle au Département de Géographie Université de Montréal et à l'Institut Méditerranéen d'Écologie et de Paléoécologie Université de Droit, d'Économie et de Sciences d'Aix-Marseille 111 / La tourbière de Mirabel (basses terres du St-Laurent, Québec méridional) a été étudiée dans le but de préciser l'influence exercée par les différents paramètres autogènes et allogènes sur l'accumulation postglaciaire du carbone. (l) Les dynamiques végétales régionales révèlent un contrôle climatique général, modulé localement par le contexte paléogéographique, la physiographie et les processus écologiques. (2) L'histoire postglaciaire du climat régional fut reconstituée par la méthode des analogues modernes, contrainte par les fluctuations du niveau du lac Hertel (Mont St-Hilaire). Les résultats obtenus témoignent d'un important réchauffement entre 13 000 et 11 000 cal. BP, d'un optimum thermique autour de 8000 cal. BP, et de deux périodes sèches (10 000-6500 et 5000-3000 cal. BP). (3) Les dynamiques postglaciaires internes de la tourbière furent indépendamment reconstituées en trois dimensions par l'analyse pluridisciplinaire de sept profils. Ces derniers montrent des successions végétales similaires, conformes au modèle de terrestrialisation, mais asynchrones. Ils témoignent en outre de conditions de surface très humides avant 6700 cal. BP, suivies de nombreuses fluctuations asynchrones sur l'ensemble du site. L'accumulation du carbone présente en revanche des tendances similaires dans tous les profils, caractérisées par de fortes accumulations avant 6200 cal. BP (moyennes de 7.1 à 19.1 gC.m .an'1) et de faibles accumulations depuis (moyennes de 2.7 à 6.3 gC.m'2.an ). (4) Les différentes conditions postglaciaires du développement de la tourbière sont confrontées. L'accumulation du carbone paraît avoir été essentiellement contrôlée par les interrelations entre la physiographie (alimentation minérotrophe initiale) et les processus autogènes, qui ont progressivement isolé la végétation tourbigène de la nappe phréatique. Notamment, ni le climat, ni les feux ne semblent avoir joué de rôle significatif. / Mirabel bog (St. Lawrence lowlands, southern Quebec) was studied with the aim to specify the influences exerted by the different autogenic and allogenic parameters on postglacial carbon accumulation. (1) Regional vegetation dynamics reveal a general climatic control, locally modified by the palaeogeographical context, physiography and ecological processes. (2) The postglacial history of the regional climate was reconstructed by the modem analogues method, constrained by the water level fluctuations of Lac Hertel (Mont St- Hilaire). Obtained results provide evidence for an important climate improvement between 13 000 and 11 000 cal. BP, a thermal optimum around 8000 cal. BP and two dry periods (10000-6500 and 5000-3000 cal. BP). (3) Postglacial internal dynamics were independently reconstmcted in three dimensions by the multidisciplinary analysis of seven profiles. They show similar plant successions, conforming to the terrestrialisation model but were asynchronous. They moreover attest the occurrence of very humid conditions prior to 6700 cal. BP, followed by numerous asynchronous fluctuations throughout the site. By contrast, carbon accumulation presents similar trends in all proiïles, characterised by high accumulation rates prior to 6200 cal. BP (averages from 7.1 to 19.1 gC.m .year ) and low rates since this date (averages from 2.7 to 6.3 gC.m'2.year-l). (4) The different postglacial conditions of peatland development arc coirfronted. Carbon accumulation appears to have been essentially controlled by the interplay between physiography (initial minerotrophic supply) and autogenic processes, which progressively isolated the peat-forming vegetation from groundwater. Notably, neither climate nor fire seem to have played a significant role.
359

Multispectral imaging of Sphagnum canopies: measuring the spectral response of three indicator species to a fluctuating water table at Burns Bog

Elves, Andrew 02 May 2022 (has links)
Northern Canadian peatlands contain vast deposits of carbon. It is with growing urgency that we seek a better understanding of their assimilative capacity. Assimilative capacity and peat accumulation in raised bogs are linked to primary productivity of resident Sphagnum species. Understanding moisture-mediated photosynthesis of Sphagnum spp. is central to understanding peat production rates. The relationship between depth to water table fluctuation and spectral reflectance of Sphagnum moss was investigated using multispectral imaging at a recovering raised bog on the southwest coast of British Columbia, Canada. Burns Bog is a temperate oceanic ombrotrophic bog. Three ecohydrological indicator species of moss were chosen for monitoring: S. capillifolium, S. papillosum, and S. cuspidatum. Three spectral vegetation indices (SVIs) were used to characterize Sphagnum productivity: the normalized difference vegetation index 660, the chlorophyll index, and the photochemical reflectance index. In terms of spectral sensitivity and the appropriateness of SVIs to species and field setting, we found better performance for the normalized difference vegetation index 660 in the discrimination of moisture mediated species-specific reflectance signals. The role that spatiotemporal scale and spectral mixing can have on reflectance signal fidelity was tested. We were specifically interested in the relationship between changes in the local water table and Sphagnum reflectance response, and whether shifting between close spatial scales can affect the statistical strength of this relationship. We found a loss of statistical significance when shifting from the species-specific cm2 scale to the spectrally mixed dm2 scale. This spatiospectral uncoupling of the moisture mediated reflectance signal has implications for the accuracy and reliability of upscaling from plot based measurements. In terms of species-specific moisture mediated reflectance signals, we were able to effectively discriminate between the three indicator species of Sphagnum along the hummock-to-hollow gradient. We were also able to confirm Sphagnum productivity and growth outside of the vascular growing season, establishing clear patterns of reflectance correlated with changes in the local moisture regime. The strongest relationships for moisture mediated Sphagnum productivity were found in the hummock forming species S. capillifolium. Each indicator Sphagnum spp. of peat has distinct functional traits adapted to its preferred position along the ecohydrological gradient. We also discovered moisture mediated and species-specific reflectance phenologies. These phenospectral characteristics of Sphagnum can inform future monitoring work, including the creation of a regionally specific phenospectral library. It’s recommended that further close scale multispectral monitoring be carried out incorporating more species of moss, as well as invasive and upland species of concern. Pervasive vascular reflectance bias in remote sensing products has implications for the reliability of peatland modelling. Avoiding vascular bias, targeted spectral monitoring of Sphagnum indicator species provides a more reliable measure for the modelling of peatland productivity and carbon assimilation estimates. / Graduate
360

Tvorba odtoku a jeho dynamika v pramenné oblasti Otavy / Streamflow generation process and its dynamics in the Otava river headwaters

Kocum, Jan January 2012 (has links)
In context of catastrophic floods and extreme droughts in recent years there is an urgent need of solving of issues dealing with protection against hydrological extremes, not using just classical engineering methods but also untraditional practices. There is a new protection strategy focusing on gradual increase of river catchment retention capacity including its headwater regions. All of the issues related to various possibilities and measures leading to river headstream areas retention capacity increase should be discussed by experts in various fields taking into account objectives and priorities of a supra-regional, regional and local significance. Natural runoff process is affected by man already by its birth, thus in headwaters where numerous procedures related to runoff retardation and water retention increase in headstream areas could be realized. Suitable conditions for the research realization at present is related to the Otava River headwaters (sw. Czechia) representing the core zone of a number of extreme runoff events and with high heterogeneity in the terms of physical-geographic and socio-economic aspects. To understand and clarify the runoff generation process and the effect of various physical-geographic factors on its dynamics, the detailed analyses of runoff regime in chosen...

Page generated in 0.0928 seconds