Reliable, efficient and cost-effective energy supply is crucial for economic and social development. Mining and industrial sectors consumed close to 37% of the total energy produced in the world during 2013. The South African power network is strained by the rapid expansion of mining, industrial and public sectors. Generation, transmission and distribution of electrical energy are in progress, but supply will not meet demand in the near future. The South African electricity supplier needs capital for expansion. Electricity price increases have been significantly higher than increases in the gold price over the last few years. Mining companies are under pressure from government to improve their labour relations. They are obligated to spend money on local infrastructure development. Therefore, cost efficiency receives higher priority than ever before and requires an implementation strategy. Cooling systems on mines proved to be significant electricity consumers. These systems lack integrated management and efficient and optimised control. Electricity demand can be reduced through implementation of energy saving measures on these cooling systems. Energy saving measures reduce the operational costs of mining to ensure that mines stay globally competitive. The identification of long-term challenges for energy saving measures is crucial. Successful implementation of energy saving measures results in improved utilisation and performance of mine cooling systems. These measures must be maintained to ensure a constant positive impact on reduced electrical energy consumption. The electrical energy savings are dependent on external factors, such as ambient conditions. Improved implementation strategies of energy saving measures will prevent deterioration of utilisation and performance of the mine cooling systems. Monitoring and reporting of key performance indicators are crucial. Lack of integrated maintenance can lead to lost opportunities and the deterioration of equipment and machines. The improved implementation strategies in two separate case studies proved sustainable savings of 1.73 MW and 0.66 MW respectively. The electricity cost savings for Mine A and Mine B are R8.8 million and R2.9 million respectively. These savings have been sustained for periods of seventeen and seven months respectively, indicating the value of the study. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: A 1.5 x 1.5 m2 counter-flow fill performance test facility is described in detail. Instrumentation was selected and installed in the cooling tower fill test facility and calibrated to ensure measurement accuracy. A facility control program was written to simplify the operation of the test facility via a user interface. The program calculates automatically the Merkel number and loss coefficients as measures of fill thermal and flow performance respectively. A spray frame was designed and manufactured to ensure uniform water distribution to the fill. The water distribution through different fills with varying fill heights and different water flow rates was measured. The water attached to the walls of the test facility was examined. Film, trickle and splash fills are tested in the upgraded test facility. The film and trickle fill performance determined during testing is deemed acceptable as these fills have minimal migration effects. Fills with poor distribution effects and large migration of water towards the walls of the test facility, like the splash fill tested, cannot to be tested accurately in a 1.5 x 1.5 m2 test section as the results do not represent the performance of the fill in a relatively large cooling tower. Other aspects examined were: • air flow uniformity • air fill bypass effects • location of water inlet and outlet temperature measurement points • location of pressure measurement probes. It was determined that, in the current test facility: • air uniformity is suitable for performance testing • air bypass effects can be ignored for open fills and can be minimised for dense fills by packing sponge between the fill and walls • water inlet and outlet temperatures should be measured in the pipe-work, resulting in a measurement method that is not influenced by the relative weightings of each thermocouple • pressure difference over the fill height measured by the pressure measurement tap is independent of its location on the fill outlet plane provided the pressure measurement points are perpendicular to the air stream and are not against the walls. / AFRIKAANSE OPSOMMING: 'n 1.5 x 1.5 m² Teenvloei pakking werkverrigting toetsfasiliteit word in detail beskryf. Instrumentasie is gekies en geïnstalleer in die koeltoring pakking toetsfasiliteit en gekalibreer om akkuraatheid te verseker. 'n Fasiliteit beheer program is geskryf om die gebruik van die toetsfasiliteit te vereenvoudig. Die program het ‘n vriendelike gebruikers intervalk. Die program bereken outomaties die Merkel-getal en verlies koëffisiënte as mate van pakking termiese- en vloeiwerksverrigting. 'n Sproeiraam is ontwerp en vervaardig om uniforme water verspreiding aan die pakking te verseker. Die water verspreiding deur verskillende pakkings met verskillende pakking hoogtes en water vloei snelhede is gemeet. Die water aangeheg aan die mure van die toetsfasiliteit is ook ondersoek. Film, druppel en spat pakkings word in die opgegradeerde toetsfasiliteit getoets. Die film- en druppelpakking werksverrigting bepaal tydens die toetse is aanvaarbaar, aangesien hierdie pakkings minimale migrasie effekte het. Pakking met swak verspreiding effekte en 'n groot migrasie van water na die wande van die toetsfasiliteit, soos gevind met die spatpakking toetse, kan nie met akkuraatheid in 'n 1.5 x 1.5 m² toets seksie getoets word nie omdat die resultate nie die werkverrigting van die pakking verteenwoordig in 'n relatief groot koeltoring. Ander aspekte wat ondersoek was: • lugvloei uniformiteit • lug omleiding effeckte • die posisie van water in- en uitlaat temperatuur meetpunte • posisie van die drukmeetapparaat. Dit is vasgestel dat, in die huidige toetsfasiliteit • lugvloei eenvormigheid geskik is vir prestasietoetsing • lug omleiding effekte kan geïgnoreer word vir oop pakkings en kan verklein word vir digte pakkings deur spons tussen die pakking en mure te pak • water inlaat- en uitlaattemperature behoort gemeet te word in die pypwerk en lei tot 'n metings metode wat nie beïnvloed word deur die relatiewe gewigte van elke thermokoppel nie • die druk verskil gemeet deur die drupmeetpunte oor die pakkinghoogte is onafhanklik van hul posisie op die pakkinguitlaatvlak op voorwaarde dat die drukmeetpunte loodreg is teen die lugstroom en nie teen die mure nie.

O gerenciamento de recursos hídricos se propõe a resolver os problemas resultantes do uso intensivo da água, produto do crescimento econômico e populacional, e preservar as funções hidrológicas, biológicas e químicas dos ecossistemas, assim como garantir que esse recurso se mantenha com oferta adequada. No Brasil, país cujas dimensões são continentais, o controle dos cursos de água frequentemente acaba não englobando todas as regiões de interesse de um estudo. Conhecida esta carência, a técnica conhecida como Regionalização Hidrológica aparece como uma opção para a obtenção de informações hidrológicas em regiões sem ou com poucos dados, fundamentando-se na similaridade espacial de algumas funções, variáveis e parâmetros que toleram essa transferência. Diante dos diversos modelos de regionalização desenvolvidos e da necessidade de obtenção das informações hidrológicas de forma facilitada, é fundamental o estudo comparativo de metodologias de regionalização de vazões com o objetivo de se conhecer a mais adequada às características regionais de cada bacia hidrográfica. Neste sentido, o objetivo geral deste trabalho foi avaliar as estimativas da vazão de referência Q7,10 e também das vazões mínimas de permanência na bacia do Rio Jaguari (divisa dos estados de Minas Gerais e São Paulo e importante afluente do Sistema Cantareira) obtidas por diferentes técnicas de regionalização, quais sejam, os métodos propostos por Liazi et al. (1988) e Wolff et al. (2014) para o Estado de São Paulo e o IGAM (2012) para o Estado de Minas Gerais. O estudo foi realizado na Bacia Hidrográfica do Rio Jaguari, a qual localiza-se entre os estados supracitados. A partir dos dados históricos de vazão das estações presentes nesta Bacia Hidrográfica foram calculadas a Qmed, Q90, Q95 e Q7,10 referente a cada uma das cinco estações fluviométricas estudadas. Em seguida, estas mesmas variáveis foram estimadas utilizando as metodologias de regionalização propostas por Liazi et al. (1988), Wolff et al. (2014) e IGAM (2012). A fim de se definir qual o método de regionalização hidrológica mais adequado para a região do alto do Rio Jaguari, os resultados das vazões calculadas por intermédio das séries históricas colhidas por estações fluviométricas foram comparadas com as estimadas pelos modelos suprecitados mediante análise de índices estatísticos, tais como, índice de concordância (d), teste de eficiência de Nash-Sutcliffe (NSE), viés percentual (PBIAS), razão entre o erro médio quadrático e o desvio padrão dos dados observados (RSR) e o coeficiente de determinação (R2). O modelo de Liazi et al. (1988) apresentou ajuste, classificado pelo índice de concordância (d), teste de eficiência de Nash-Sutcliffe (NSE) e o coeficiente de determinação (R2), como muito bom, mostrando-se superior aos demais métodos nessa região. A metodologia de IGAM (2012) demonstrou ajuste insatisfatório para os indicadores estatísticos NSE, PBIAS e índice d e muito bom para o coeficiente de determinação (R2). A nova proposta de Regionalização Hidrológica para o estado de São Paulo de Wolff et al. (2014) apresentou ajuste, classificado pelos índices de concordância (d), teste de eficiência de Nash-Sutcliffe (NSE), viés percentual (PBIAS) e coeficiente de determinação (R2), como, no geral, insatisfatório; por outro lado o comportamento gráfico dos resultados obtidos demonstrou potencialidade para o uso desse método. Recomenda-se a aplicação de estudos comparativos semelhantes em outras Sub- Bacias localizadas entre os estados de Minas Gerais e São Paulo para corroborar ou não com as conclusões do presente trabalho. / Water resources management is meant to solve problems caused by the intensive use of this resource, which is the product of economic and population growth. Water resources management is also responsable for preserving the hydrological, biological and chemical functions of ecosystems, as well as ensure that this resource is maintained with the adequate supply for future generations. In Brazil, a country with continental dimensions, streamflow gauge coverage is far from satisfactory. Therefore, the Hydrological Regionalization technique is as an option to estimate hydrological information in regions with few or no data. This methodology is based on the spatial similarity of functions, variables and parameters that tolerate this transference. The number of regionalization models and the need to easily access hydrological data transformed comparative studies of streamflow regionalization methodologies into a fundamental topic in Hydrology. For this reason, the was the goal of this paper is to assess the models settled by Liazi et al. (1988), Wolff et al. (2014) and IGAM (2012) related to the variables Q7,10, Q90, Q95 and Qmed in Jaguari River Basin, which is located between Minas Gerais and São Paulo states and constitutes an important affluent to the Cantareira System. Firstly, the Q7,10, Q90, Q95 and Qmed were calculated using the historical flow data from five fluviometric stations located in Jagari River Basin. Then, these same variables were estimated using the regionalization methodologies proposed by Liazi et al. (1988), Wolff et al. (2014) and IGAM (2012). In order to determine the best hydrological regionalization method for the upper Jaguari River Basin, the flow rates results calculated with the historical series were compared to those estimated by the models. The forecast was determined utilizing the following indicators: index of agreement (d), Nash-Sutcliffe efficiency (NSE), percent bias (PBIAS), the ratio of the root mean square error to the standard deviation of measured data (RSR) and coefficient of determination (R2). Liazi et al. (1988) presented the best performance when compared to the other two methods, its behavior was classified as very good by the index of agreement (d), the Nash-Sutcliffe efficiency (NSE) and the coefficient of determination (R2). IGAM (2012) exhibited an unsatisfactory fit for the statistical indicators of NSE and PBIAS. On the other hand, this method was classified as very good when the coefficient of determination (R2) was analyzed. The new proposal of Hydrological Regionalization for São Paulo state (WOLFF et al., 2014) presented an adjustment, classified by the index of agreement (d), the Nash-Sutcliffe efficiency (NSE), the percentage bias (PBIAS) and coefficient of determination (R2), as unsatisfactory, in general. The graphical behavior, however, demonstrated a good potential for future use. In conclusion, it is recommended to apply similar comparative studies in other sub-basins located between the states of Minas Gerais and São Paulo to corroborate or not with the presented results.

A demanda alimentar vem aumentando de acordo com o crescimento populacional e com isso há uma necessidade de que as práticas agrícolas tornem-se cada vez mais intensas e tecnificadas, mediante o incremento, entre outros, da utilização de insumos químicos. Porém, uma vez aplicados de maneira desorganizada, sem a devida preocupação com os possíveis impactos aos recursos naturais, tais produtos podem vir a provocar danos ao solo, contaminação de águas subterrâneas (mediante sua lixiviação) e em alguns casos, podem ser responsáveis pelo aumento da salinidade em alguns solos da região do semiárido do nordeste brasileiro. Nesse sentido, devido ao fato de envolverem processos físicos na natureza, o estudo da dinâmica desses produtos químicos têm motivado diversos pesquisadores a aplicarem ferramentas matemáticas (modelos matemáticos) na área de engenharia de água e solo, buscando entender a correlação entre a dinâmica da água e o movimento de solutos no perfil do solo. Portanto, a presente pesquisa tem como objetivo a aplicação do modelo matemático HYDRUS-1D para a simulação do movimento da água e do íon potássio, em condições de laboratório, utilizando-se colunas preenchidas com dois tipos de material de solos salinos e não saturados: Argissolo Amarelo (S1) e Latossolo Vermelho Amarelo (S2). Além disso, buscou-se também avaliar tanto o desempenho do referido modelo, em condições salinas, quanto proceder a uma análise de sensibilidade. Para alcançar tais objetivos, foram conduzidas as seguintes etapas: 1) elaboração de curvas de distribuição de efluentes (Breakthrough Curves - BTC) para obtenção dos parâmetros de transporte do íon potássio, com a aplicação de soluções de 1000 ppm, 2000 ppm e 3000 ppm de concentração de potássio, nos dois tipos de solos salinos, 2) Aplicação dessas soluções de potássio na coluna preenchida com o mesmo material de solo salino não saturado, 3) Simulação dos perfis de água e potássio para os diferentes materiais de solo salino pelo modelo HYDRUS-1D e 4) Avaliação de desempenho e análise de sensibilidade do modelo HYDRUS-1D. A avaliação de desempenho foi feita levando-se em conta os seguintes índices estatísticos: erro máximo, erro absoluto médio, raiz quadrada do erro médio normalizado, coeficiente de massa residual, coeficiente de determinação, eficiência e índice de concordância de Willmott e a análise de sensibilidade foi feita mediante a determinação do erro padrão, por meio de variações positivas (+ 10%, + 20%, + 30%, + 40%, + 50%) e negativas (- 10%, - 20%, - 10%, - 40%, - 50%), dos valores de: umidade volumétrica do solo saturado, condutividade hidráulica e os parâmetros n e ? do modelo de van Genuchten (1980). Diante dos resultados obtidos, pôde-se perceber que os procedimentos experimentais (BTC\'s) para a estimativa dos parâmetros de transporte do íon potássio em condições de solo salino, foram suficientes para descrever a movimentação do íon potássio no solo, gerando informações de entrada precisas para os modelos de simulação. Em termos do modelo HYDRUS-1D, observou-se que o deslocamento do íon potássio acompanhou a frente de molhamento e que o modelo foi eficiente nas simulações de deslocamento do íon potássio e da água para ambos os solos, em condições salinas. A análise de sensibilidade evidenciou que o modelo apresentou-se sensível, às variações negativas dos dados de entrada: umidade volumétrica do solo saturado, condutividade hidráulica do solo saturado e parâmetros \"n\" e \"?\" do modelo de van Genuchten (1980). / The increased demand for food due to population growth requires that agricultural practices become increasingly intensive and very technical, including the increased use of agricultural chemicals (fertilizers). If improperly applied without considering possible impacts on natural resources, agricultural chemicals may lead to soil and groundwater contamination through their leaching from the soil root zone. They may be responsible also for increased salinity in some soils of semiarid regions in northeastern Brazil. Since many transient physical and chemical processes affect their transport in the subsurface, mathematical models have become popular tools in soil and water engineering and management in order to understand the correlation between water dynamics and solute movement in soils. Thus, this research aimed at using the HYDRUS-1D software package to simulate water and potassium movement, under laboratory conditions, in unsaturated saline soil columns filled with two soil types: an Ultisol (S1) and an Oxisol (S2). Comparisons were made with experimental data while also a sensitivity analysis was carried out to evaluate the effect of various parameters on solute transport under saline conditions. For this purpose the following studies were performed: 1) Measurement of solute breakthrough curves (BTCs) to estimate the transport parameters of the potassium ion by applying potassium solutions of 1,000 ppm, 2,000 ppm and 3,000 ppm to both soil types, 2) Application of similar potassium solutions to columns containing the same saline unsaturated soils, 3) Simulation of water and potassium distributions for different saline soil materials using HYDRUS-1D, and 4) Performance evaluation and sensitivity analyses of the HYDRUS-1D numerical model. The performance evaluation was conducted using the following statistical indices: maximum error, mean absolute error, normalized root mean square error, coefficient of residual mass, coefficient of determination, efficiency and Willmott\'s concordance index. The sensitivity analyses considered standard deviations resulting from positive and negative changes (+ 10% + 20% + 30% + 40% + 50%) (-10%, -20%, -10%, -40%, -50%) in the values of the saturated volumetric soil moisture content, the saturated hydraulic conductivity, and the parameters n and ? of van Genuchten\'s (1980) model for the unsaturated soil hydraulic functions. Results indicate that the experimental procedures (BTCs) for estimating the transport parameters of potassium for saline soil conditions were sufficient to describe potassium ion transport in the soils by generating the required input information for the simulation models. Relative to HYDRUS-1D model, the displacement of potassium was found to follow closely the wetting front, with the model providing a very efficient means for simulating the movement of both water and potassium in the two soils during saline conditions. The sensitivity analysis showed that the model was relatively sensitive to negative variations of the input data, notably the saturated water content, the saturated hydraulic conductivity, and the n and ? soil hydraulic parameters.

A presente dissertaÃÃo apresenta como objetivo principal a instalaÃÃo e avaliaÃÃo de desempenho tÃcnico-financeiro de um sistema hÃbrido eÃlico-fotovoltaico aplicado ao bombeamento de Ãgua. Adicionalmente, à proposta uma metodologia de dimensionamento de sistema hÃbrido de geraÃÃo baseado em fontes renovÃveis em funÃÃo do menor custo e do potencial disponÃvel. O sistema de geraÃÃo hÃbrido foi instalado na jusante do aÃude do Campus do Pici da Universidade Federal do Cearà (UFC), em Fortaleza/CE, Brasil. O sistema hÃbrido à composta por 01 aerogerador de 1 kW, 04 mÃdulos fotovoltaicos de 87 Wp, sistema de banco de baterias com 05 unidades de 150 Ah. O sistema de bombeamento à composto por um conjunto moto-bomba de 0,5 cv. A anÃlise tÃcnica foi efetuada mediante anÃlise dos dados (elÃtricos e nÃo elÃtricos) coletados atravÃs de sensores instalados a um sistema supervisÃrio. Os resultados indicam que a variaÃÃo do recurso eÃlico para o local à mais elevada, quando comparado ao recurso solar, e que a disponibilidade do potencial de ambos os recursos sÃo praticamente concomitantes ao longo do perÃodo diurno, caracterÃstica esta tambÃm observada no perÃodo analisado. O sistema de geraÃÃo com banco de baterias, operando tanto na configuraÃÃo hÃbrida ou individual, assegurou o fornecimento de eletricidade para o sistema de bombeamento no perÃodo de funcionamento da carga. A partir dos indicadores de eficiÃncia, verificou-se que as unidades de conversÃo apresentaram divergÃncia entre a geraÃÃo de eletricidade estimada e a mensurada, tendo a unidade eÃlica a qual apresentou maior divergÃncia. O custo da energia elÃtrica do sistema hÃbrido instalado (eÃlico-solar) com banco de baterias à de 0,86 R$/kWh. O dimensionamento do sistema de geraÃÃo indicou que a configuraÃÃo hÃbrida para o local nÃo se ajusta em virtude do elevado potencial solar disponÃvel e da baixa disponibilidade do recurso eÃlico no 1 trimestre do ano. O dimensionamento indicou que a configuraÃÃo hÃbrida foi a de menor custo (1,52 R$/kWh) quando dimensionada em funÃÃo dos recursos do mÃs de Outubro. Indicando assim que quando mais de uma fonte renovÃvel se destaca a configuraÃÃo hÃbrida pode ser sim uma alternativa viÃvel. / This work has as main objective the installation and technical - financial evaluation of a hybrid wind - photovoltaic system applied to water pumping . In addition, a sizing methodology is proposed based on renewable sources considering low cost and available potential. The hybrid system was installed in front of the Pici Campus reservoir of the Federal Univers ity of Cearà (UFC) in Fortaleza /CE, Brazil. The hybrid system consists of 01 wind turbine of 1 kW, 04 photovoltaic modules of 87 Wp, a battery bank with 05 units of 150 Ah. The pumping system con sists of a motor - pump 0, 5 cv . Technical analysis was performed by analyzing the data (electric and non - electric) collected by sensors to a supervisory system. The results indicate that the wind resource variation for the site is higher, when compared to the solar resource, and the availability of the potential of both resources are concomitant during the daytime period, a characteristic also observed in the anal yzed period. T he generation system with battery bank, operating in either the hybrid configuration or individual, assured the supply of electricity to the pumping system during operating time . From the indicators of efficiency, it was found that the conver sion units showed divergence between estimated and measured electricity generation, and wind unit which presented greater divergence. The electricity cost of the hybrid system (wind - solar) installed with battery bank is 0.86 R$/kWh. The sizing of the generating system indicated that the hybrid configuration at the site does not fit due to the high solar potential available and the low availability of wind resources in the 1 st trimester of the year . The sizing generation system indicated that th e hybrid configuration has the lowest cost (1.52 R$/kWh) when sizing with the resources of October month . Indicating thus , that when more than one renewable source stands out , the hybrid configuration can be viable alternative

<p>Nedbrytning av organiskt material är en nyckelfaktor som påverkar omvandlingar av de många grundämnen som utgör eller är associerade till just organiskt material. En stor del av nedbrytningen av akvatiskt organiskt material (OM) sker i gränsskiktet mellan sediment och vatten. Eftersom så många biogeokemiska cykler styrs av nedbrytningen av OM är det viktigt att ha kunskap om processer och påverkansfaktorer både på mikro- och makronivå. Mineraliseringshastigheten av OM är en vanligt förekommande mätparameter, men vanligtvis inkluderar mätningarna inte de naturliga processer som kan påverka nedbrytnings-hastigheterna, t.ex. fysiska krafter.</p><p>Syftet med den här studien är att studera mineraliseringshastigheten av det OM som finns naturligt i ytsediment i söt- och brackvatten när det utsätts för fysiska krafter som orsakar förändringar i redox-förhållanden, resuspension eller advektivt porvattenflöde. Fem</p><p>laborativa experiment har utförts för att belysa syftet:</p><p>Åldrat ytsediment från en sötvattens å utsattes för olika redox förhållanden där oxisk respiration, sulfatreduktion respektive metanogenes gynnades. Resultaten visade ingen skillnad i mineraliseringshastighet beroende på behandling. Detta motsäger studier utförda i marina miljöer, där anoxiska förhållanden ger en lägre mineraliseringshastighet än oxiska.</p><p>Vidare gjordes två studier på brackvattensediment där effekten av resuspension var i centrum. Den ena studien fokuserade på frekvens och varaktighet av resuspensionstiderna, den andra på olika typer av sediment. Studierna visade att väldigt korta resuspensionstider med upp till 48 timmars stillhet mellan varje resuspension ökade mineraliseringstakten med fem gånger jämfört med diffusivt utbyte, och mer än dubblerades i jämförelse med kontinuerlig resuspension eller resuspension i långa perioder. Resuspensionen under kort tid var troligen gynnande då resuspension fysiskt stör bildningen av stabila bakteriesamhällen. Mineraliseringshastigheterna i sediment som domineras av väldigt fin, fin eller medium sand visade lika hastigheter, medan grov sand visade en signifikant lägre mineraliseringshastighet. Likheterna mellan de tre första sedimenttyperna kan dock ha påverkats av tillgång på lättnedbrytbart OM då sediment och vatten hämtades in under en algblomning.</p><p>Till sist studerades effekten på mineraliseringshastigheten av advektivt porvattenflöde. Detta gjordes på åldrat sediment dels från en sötvattensbäck dels från en brackvattenstrand. Inget av de två sedimenttyperna visade någon skillnad i mineraliseringshastighet i jämförelse med diffusivt styrda system. Det är i motsats till tidigare marina studier, men är i linje med den första studien, där mineraliseringshastigheten var oberoende av redox-förhållande.</p><p>Den generella slutsatsen från den här studien är nödvändigheten att studera samma aspekter i olika typer av akvatiska system, eftersom responsen verkar vara annorlunda beroende på system, t.ex. söt- brack- och saltvatten. Faktorer som kan förklara de här skillnaderna finns ännu inte, vilket gör att småskaliga studier och modeller blir viktiga verktyg för att utreda detta.</p> / <p>Organic matter mineralisation is a key parameter that affects most other element transformations associated with organic matter. A substantial part of aquatic organic matter (OM) mineralisation takes place at the interface between sediment and water. Understanding OM mineralisation is important at both the micro and macro scales, since it drives many biogeochemical cycles. OM mineralisation rates are widely measured, but generally not all the natural factors possibly affecting the rates, such as physical forcing, are considered.</p><p>This thesis examines the mineralisation rates of indigenous OM in fresh and brackish surface sediments, subjected to different physical forces inducing changed redox conditions, resuspension, and advective pore water flow. Five experiments were performed to this end.</p><p>Aged surface sediment from a freshwater river was subjected to different redox conditions favouring oxic respiration, sulphate reduction, and methanogenesis, respectively. Results indicated no difference in mineralisation rate irrespective of treatment. This contradicts what has been found in marine environments, where anoxic mineralisation rates are lower than oxic ones.</p><p>Further, two studies of resuspension of brackish sediments were performed, one addressing the impact of the frequency and duration of the resuspension events, and the other addressing the impact of resuspension on different types of sediments. The studies found that very brief resuspension events followed by calm periods of up to 48 h increased mineralisation rates by five times compared to diffusion, and more than doubled the rate compared to continuous or long-term resuspension. The short-term events were possibly favoured because resuspension physically disturbs the arrangement of a stable bacteria community. Mineralisation rates on sediments dominated by very fine, fine, or medium-grained sand were the same, while coarse sand displayed a significantly lower rate. The similar rates of the three first sediment types could stem from access to labile OM, due to an ongoing algae bloom when the sediment and water samples were collected.</p><p>Finally, the effect of advective pore water flow on aged sediment from one fresh and one brackish sediment was studied. Neither of the sediments displayed a mineralisation rate different from those occurring in incubations in which only diffusive exchange occurred. This contradicts the findings of previous marine studies, but is in line with the first study, which did not detect different mineralisation rates irrespective of redox conditions.</p><p>The general conclusion is that it is necessary to study the same physical forces in different aquatic environments, since responses appear to differ, for example, between freshwater, brackish, and marine environments. Factors explaining these differences have not yet been expressed, making small-scale studies and modelling a challenge for future research.</p>

Canadian agriculture trade with the United States, specifically trade in livestock and livestock commodities, has flourished under the NAFTA regime. However, the benefits of this trade liberalization have hidden environmental costs that seldom get noticed or accounted. The purpose of this research was to evaluate the hidden cost on water resources by first assessing the virtual water content (VWC) of various types of livestock and livestock products and then quantifying the virtual water flow (VWF) related to trade in livestock and its products between Canada and United States. The study also examined the North American Free Trade Agreement (NAFTA) and evaluated its implications for Canadian water resources. The research was conducted in three parts. First, the background literature on NAFTA was studied and trade data were collected to understand the NAFTA regime and study the impacts on Canadian exports of livestock and livestock products from the 1990s. The trade data were collected from provincial agricultural ministries and Statistics Canada. Secondly, datasheets were created to calculate the VWC in the various categories of animals and ultimately to estimate VWF between the two countries. Finally, Alberta and Ontario were chosen as case study areas to investigate localized impacts on water resources due to trade under NAFTA. The research results indicate that there is a large difference in the amount of VW being transferred through livestock and livestock commodities from Canada to the U.S. The average difference in trade has been calculated to be 3.6 billion m3 per year. This makes Canada a net exporter of virtual water to the U.S. A closer look at the trade patterns reveals that the U.S. imports mostly water-intensive commodities like cattle and cattle commodities, while it exports mostly less-water intensive commodities like chicken and mutton. By eliminating numerous trade barriers, the agreement has allowed competitive market forces to play a more dominant role in determining agricultural trade flows between the two countries. NAFTA has been criticized and contested at different levels for encouraging bulk water export from Canada to the U.S. What has not received attention in this debate is that water is also being exported in other forms, i.e., the virtual form. The hidden environmental, costs (for the exporting countries) or benefits (to the importing countries) are not reflected in the pricing of agricultural commodities. NAFTA’s mandate for the expansion of trade and investment through the removal of all trade barriers between the two countries is encouraging increased VW trade. This trade, if overlooked, can have deleterious impacts on the water resources of Canada.

Canadian agriculture trade with the United States, specifically trade in livestock and livestock commodities, has flourished under the NAFTA regime. However, the benefits of this trade liberalization have hidden environmental costs that seldom get noticed or accounted. The purpose of this research was to evaluate the hidden cost on water resources by first assessing the virtual water content (VWC) of various types of livestock and livestock products and then quantifying the virtual water flow (VWF) related to trade in livestock and its products between Canada and United States. The study also examined the North American Free Trade Agreement (NAFTA) and evaluated its implications for Canadian water resources. The research was conducted in three parts. First, the background literature on NAFTA was studied and trade data were collected to understand the NAFTA regime and study the impacts on Canadian exports of livestock and livestock products from the 1990s. The trade data were collected from provincial agricultural ministries and Statistics Canada. Secondly, datasheets were created to calculate the VWC in the various categories of animals and ultimately to estimate VWF between the two countries. Finally, Alberta and Ontario were chosen as case study areas to investigate localized impacts on water resources due to trade under NAFTA. The research results indicate that there is a large difference in the amount of VW being transferred through livestock and livestock commodities from Canada to the U.S. The average difference in trade has been calculated to be 3.6 billion m3 per year. This makes Canada a net exporter of virtual water to the U.S. A closer look at the trade patterns reveals that the U.S. imports mostly water-intensive commodities like cattle and cattle commodities, while it exports mostly less-water intensive commodities like chicken and mutton. By eliminating numerous trade barriers, the agreement has allowed competitive market forces to play a more dominant role in determining agricultural trade flows between the two countries. NAFTA has been criticized and contested at different levels for encouraging bulk water export from Canada to the U.S. What has not received attention in this debate is that water is also being exported in other forms, i.e., the virtual form. The hidden environmental, costs (for the exporting countries) or benefits (to the importing countries) are not reflected in the pricing of agricultural commodities. NAFTA’s mandate for the expansion of trade and investment through the removal of all trade barriers between the two countries is encouraging increased VW trade. This trade, if overlooked, can have deleterious impacts on the water resources of Canada.

Includes vita. / Title from PDF of title page. / Document formatted into pages; contains 185 pages. / Thesis (Ph.D.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Seagrass communities are composed of numerous organisms that depend on water-column nutrients for metabolic processes. The rate at which these organisms remove a nutrient from the water column can be controlled by physical factors such as hydrodynamic regime or by biological factors such as speed of enzyme reactions. The impact of hydrodynamic regime on rates of nutrient uptake for seagrass (Thalassia testudinum) communities and for organisms that comprise the community (seagrass, epiphytes, phytoplankton, and microphytobenthos) was quantified in a series of field flume experiments employing the use of 15N-labeled ammonium and nitrate. Rates of ammonium uptake for the entire community and for seagrass leaves and epiphytes were significantly dependent on bulk velocity, bottom shear stress, and the rate of turbulent energy dissipation. / ABSTRACT: Relationships between uptake rates and these parameters were consistent with mass-transfer theory and suggest that the effect of water flow on ammonium uptake is the same for the benthos as a whole and for the organisms that form the canopy. In addition, epiphytes on the surface of T. testudinum leaves were shown to depress leaf uptake by an amount proportional to the area of the leaf covered by epiphytes. Water flow influenced rates of nitrate uptake for the community and the epiphytes; however, uptake rates were depressed relative to those for ammonium suggesting that uptake of nitrate was also affected by biological factors such as enzyme activity. Epiphytes reduced uptake of nitrate by the leaves; however, the amount of reduction was not proportional to the extent of epiphyte cover, which provided further evidence that nitrate uptake by T. testudinum leaves was biologically limited. / ABSTRACT: As an additional component of the research, hydrodynamic regime of a mixed seagrass and coral community in Florida Bay was characterized using an acoustic Doppler velocimeter. Hydrodynamic parameters estimated from velocity data were used in mass-transfer equations to predict nutrient uptake by the benthos over a range of water velocity. Measured rates of uptake from field flume experiments conducted in the same community confirmed that hydrodynamic data could be used to accurately predict nutrient transport to the benthos under natural flow conditions. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

If air is entrained in a bottom outlet of a dam in an uncontrolled way, the resulting air pockets may cause problems such as blowback, blowout and loss of discharge capacity. In order to provide guidance for bottom outlet design and operation, this study examines how governing parameters affect air entrainment, air-pocket transport and de-aeration and the surrounding flow structure in pipe flows. Both experimental and numerical approaches are used. Air can be entrained into the bottom outlet conduit due to vortex formation at the intake if the intake submergence is not sufficient. The influent of the intake entrance profiles and channel width on the critical submergence were studied in the experiment. The experimental study was performed to investigate the incipient motion of air pockets in pipes with rectangular and circular cross sections. The critical velocity is dependent on pipe slope, pipe diameter, pipe roughness and air-pocket volume. If the pipe is horizontal, air removal is generally easier in a rectangular pipe than in a circular pipe. However, if the pipe is downward-inclined, air removal is easier in a circular pipe. When a bottom outlet gate opens, air can become entrained into the conduit in the gate shaft downstream of the gate. Using FLUENT software, the transient process of air entrainment into a prototype bottom outlet during gate opening is simulated in three dimensions. The simulations show in the flow-pattern changes in the conduit and the amount of air entrainment in the gate shaft. The initial conduit water level affects the degree of air entrainment. A de-aeration chamber is effective in reducing water surface fluctuations at blowout. High-speed particle image velocimetry (HSPIV) were applied to investigate the characteristics of the flow field around a stationary air pocket in a fully developed horizontal pipe flow. The air pocket generates a horseshoe vortex upstream and a reverse flow downstream. A shear layer forms from the separation point. Flow reattachment is observed for large air pockets. The air―water interface moves with the adjacent flow. A similarity profile is obtained for the mean streamwise velocity in the shear layer beneath the air pocket. / <p>QC 20140211</p>