Дисертації з теми "Impact sedimentation"

京都大学
新制・課程博士
博士(工学)
甲第23172号
工博第4816号
京都大学大学院工学研究科都市社会工学専攻
(主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Sameh Kantoush
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DGAM

In the Bayer processing of bauxite, dissolved silica re-precipitates as aluminosilicates or desilication products (DSPs) that adversely affect residue separation by flocculation and thickening prior to product precipitation. DSP was shown to form at the surface of hematite, impacting upon the extent, efficiency and mechanism of aggregation with a number of different polymer reagents. Real-time measurement of aggregate properties provided new insights on fines capture. The practical implications for full-scale feedwell flocculation were explored.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A água é usada para os mais variados fins: abastecimento, irrigação, geração de energia elétrica, lazer, aqüicultura, local de despejo de efluentes domésticos e industriais, etc. No caso da aqüicultura, a criação em tanques-rede introduz diretamente no corpo d’água uma grande quantidade de matéria orgânica. Essa atividade pode contribuir para acelerar os processos de eutrofização do meio devido aos aportes de nutrientes e material em suspensão provenientes, principalmente, do excedente de alimento, fezes e excretas dos peixes. Estudos sobre os impactos causados por essa atividade podem fornecer dados para uma gestão ambiental que permita otimizar o uso múltiplo dos recursos hídricos sem que haja maiores danos ao ambiente aquático. Este trabalho procurou fazer uma caracterização limnológica e uma avaliação do impacto da criação em tanques-rede de tilápia (Orechromis sp.) no córrego da Arribada (Bacia do Baixo-Tietê), que é represado pelo reservatório da Usina Hidrelétrica de Nova Avanhandava, no Rio Tietê, SP. A área destinada à piscicultura é de 4ha de espelho d’água e foi projetada para 200 tanques-rede com volume de 18m3 cada. Em sete pontos distribuídos estrategicamente na região onde foi instalado o sistema de cultivo foram analisados as seguintes variáveis: temperatura, concentração e saturação de oxigênio dissolvido, pH, transparência, e taxas de sedimentação de fósforo total, ortofosfato, nitrogênio amoniacal, nitrito, nitrato e material em suspensão por meio de câmaras de sedimentação. Os resultados mostraram mais padrões temporais que espaciais, com queda acentuada na concentração e saturação de oxigênio dissolvido e aumento nas taxas de sedimentação de fósforo total e nitrato. Apesar do impacto causado apresentar tendências preocupantes, concluiu-se que neste estudo de caso, a produção em tanques-rede é viável...
Water is used to multiple uses: water supply, irrigation, power generation, leisure, aquaculture, place of discharge of home and industrial wastes, etc. In aquaculture, cage fish farming releases a great amount of organic matter directly into the water body. This activity can accelerate the water eutrophication process due to the input of dissolved nutrients and suspended matter, mainly by diet wastes, feces and fish excreta. Studies about environmental impacts caused by this activity can provide a support for a better environmental management that allows the use of water resources without over degradation of the ecosystem. This work aimed to make a limnological characterization and evaluation of the environmental impact of cage culture of Tilapia (Oreochromis sp.) in the stream of Arribada (Tietê river basin - Brazil). This stream is partially impounded by the reservoir of the hydroelectric power station of Nova Avanhandava. The culture is placed in an area of 4ha and it is planned the installation of 200 cages of 18 m3 each one. Till December 2004, there were 180 cages, each one with 1500 to 1800kg of fish production per harvest period. Seven sampling points were strategic placed in the area where was installed the cage fish farming to analise temperature, concentration and saturation of dissolved oxigen, pH, depth and total phosphorus, ortophosfate, ammoniacal nitrogen, nitrite, nitrate and susppended matter sedimentation ratios. The results have shown more temporal then spacial patterns, with drops in concentration and saturation of dissolved oxigen in water and increase of total phosphorus and nitrate sedimentation ratios. Despite of the warning tendences, we concluded that in this study of case, the impact caused by the activity, the cage fish farming is possible, since some precautions shall be taken to avoid degradation of the water body.

Orientador: Ana Eliza Baccarin Leonardo
Banca: Abílio Lopes de Oliveira Neto
Banca: Antonio Fernando Monteiro Camargo
Resumo: A água é usada para os mais variados fins: abastecimento, irrigação, geração de energia elétrica, lazer, aqüicultura, local de despejo de efluentes domésticos e industriais, etc. No caso da aqüicultura, a criação em tanques-rede introduz diretamente no corpo d'água uma grande quantidade de matéria orgânica. Essa atividade pode contribuir para acelerar os processos de eutrofização do meio devido aos aportes de nutrientes e material em suspensão provenientes, principalmente, do excedente de alimento, fezes e excretas dos peixes. Estudos sobre os impactos causados por essa atividade podem fornecer dados para uma gestão ambiental que permita otimizar o uso múltiplo dos recursos hídricos sem que haja maiores danos ao ambiente aquático. Este trabalho procurou fazer uma caracterização limnológica e uma avaliação do impacto da criação em tanques-rede de tilápia (Orechromis sp.) no córrego da Arribada (Bacia do Baixo-Tietê), que é represado pelo reservatório da Usina Hidrelétrica de Nova Avanhandava, no Rio Tietê, SP. A área destinada à piscicultura é de 4ha de espelho d'água e foi projetada para 200 tanques-rede com volume de 18m3 cada. Em sete pontos distribuídos estrategicamente na região onde foi instalado o sistema de cultivo foram analisados as seguintes variáveis: temperatura, concentração e saturação de oxigênio dissolvido, pH, transparência, e taxas de sedimentação de fósforo total, ortofosfato, nitrogênio amoniacal, nitrito, nitrato e material em suspensão por meio de câmaras de sedimentação. Os resultados mostraram mais padrões temporais que espaciais, com queda acentuada na concentração e saturação de oxigênio dissolvido e aumento nas taxas de sedimentação de fósforo total e nitrato. Apesar do impacto causado apresentar tendências preocupantes, concluiu-se que neste estudo de caso, a produção em tanques-rede é viável ...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Water is used to multiple uses: water supply, irrigation, power generation, leisure, aquaculture, place of discharge of home and industrial wastes, etc. In aquaculture, cage fish farming releases a great amount of organic matter directly into the water body. This activity can accelerate the water eutrophication process due to the input of dissolved nutrients and suspended matter, mainly by diet wastes, feces and fish excreta. Studies about environmental impacts caused by this activity can provide a support for a better environmental management that allows the use of water resources without over degradation of the ecosystem. This work aimed to make a limnological characterization and evaluation of the environmental impact of cage culture of Tilapia (Oreochromis sp.) in the stream of Arribada (Tietê river basin - Brazil). This stream is partially impounded by the reservoir of the hydroelectric power station of Nova Avanhandava. The culture is placed in an area of 4ha and it is planned the installation of 200 cages of 18 m3 each one. Till December 2004, there were 180 cages, each one with 1500 to 1800kg of fish production per harvest period. Seven sampling points were strategic placed in the area where was installed the cage fish farming to analise temperature, concentration and saturation of dissolved oxigen, pH, depth and total phosphorus, ortophosfate, ammoniacal nitrogen, nitrite, nitrate and susppended matter sedimentation ratios. The results have shown more temporal then spacial patterns, with drops in concentration and saturation of dissolved oxigen in water and increase of total phosphorus and nitrate sedimentation ratios. Despite of the warning tendences, we concluded that in this study of case, the impact caused by the activity, the cage fish farming is possible, since some precautions shall be taken to avoid degradation of the water body.
Mestre

Research questions: This research was focused on exploring the impact of communication technologies on rural populations in the Congo. In particular, this research posed two questions: 1. Do mobile phones produce development in rural areas of the Congo? 2. Do mobile phones improve the living conditions of people? The questions helped examine ways in which mobile phones were or were not engendering development among these populations. Methods: The research was undertaken using four methods: 1. Phenomenology, 2. Sen's capability approach, 3. Participatory method, and 4. Ecological method. Phenomenology aimed to cater to the experiences and meanings of mobile phone uses. Sen's capability approach allowed the interviews to be focused on the basic needs of the poor. Participatory method provided a greater participation of respondents in discussion groups, and ecological method helped achieve a higher inclusion of key players in the targeted area. Major findings: The major findings of this study included: 1. Much of the literature on mobile phones and development was not representative or inclusive of key players and their day-to-day lives. 2. Studies have tended to present snapshots or single-focused accounts of mobile phone and development. 3. Authors of mobile phone research have tended to see rural populations with an urban-led bias, leaving aside the actual characteristics of rural areas. 4. Mobile phones were not limited to a person and her properties, but rather mobile phones were owned and shared by the community. 5. Participants expressed a need for technical skills and means to be available to the community and their members. 6. Households were not separated, but rather they were connected to allow people take care of one another. 7. People were connected through collective solidarities in order to come to the aid of those with special needs. 8. Literature and mobile phone sponsors or companies were disseminating mobile phones with an extractive and commercial tendency, focused principally on fees of batteries, chargers, and prepaid cards. Major contributions: The major contributions of this research revolved around the focus on: 1. technology to enhance the needed technical skills among concerned populations. 2. shared ownership of mobile phones to cater to both users and non-users of mobile phones among concerned populations. 3. connected households to capitalize on the dynamics of family among concerned populations. 4. collective solidarities to accommodate the processes of aiding one another among concerned populations. 5. capabilities, from a commercial or extractive aspect to capabilities to enhance the capabilities of people to afford mobile phones fees. 6. capabilities, from a corporate or business aspect to capabilities to enhance the capabilities of people who did not and could not own a business. 7. human basic needs to enhance the capabilities of mobile phone users with regard to human basic needs. 8. outliers or the marginalized to attend to those left out among concerned populations. 9. mobile phone-centric libraries to enhance the storage and retrieval of needed information among concerned populations.

The uprooting of trees due to high winds, or blowdown, is a common occurrence throughout the world. Rare, large scale blowdown events have the ability to drastically alter forest landscapes on a timescale of hours. Alone or when combined with other forest disturbances such as fires and insect outbreaks, blowdowns have the potential to modify existing watershed characteristics. Little information is known about how large-scale blowdowns affect the physical environment in general and watershed-wide sediment yield and deposition rates in particular. The few studies that have taken place have yielded inconclusive or somewhat contradictory results. Given the large scale of some events and the potential impact of such events it is important that the geomorphological effects of blowdowns be better understood, not only from a basic process but also from an applied perspective. Lakes receive and store a significant fraction of the disturbed sediment formerly found in the soil column and lake sediments have proven to be reliable and accurate records of sedimentation characteristics within their catchments. For the purpose of this study, it was hypothesized that areas subjected to blowdown will have increased erosion rates. It was also hypothesized, that lakes within blowdown areas will be subjected to accelerated sedimentation rates following events. In order to test these hypotheses and isolate the effects of a blowdown on sedimentation rate three small mountain lakes in the Mt. Zirkel Wilderness Area, Colorado were cored. The lakes selected consist of a control lake with no known recent history of blowdown in its watershed and two lakes that receive direct runoff from watersheds and slopes that were affected by a major blowdown event in 1997, the Routt-Divide Blowdown. One core was dated using the 210Pb method and multiple cores were analyzed for organic and inorganic matter concentrations to determine if changes in sedimentation rates and/or sediment compositions occurred following the event. In the case of the two lakes studied that had catchment slopes affected by blowdown, somewhat surprisingly, no significant change was observed with respect to sedimentation rates or sediment composition. In fact, sedimentation rates obtained from the dated core exhibited a decreasing trend that began decades prior to and continued through the blowdown event. This suggests that in the area affected by the Routt-Divide Blowdown it is likely that long-term changes in climate and the effect these changes have on the amount and type of vegetation present are the dominant influence on sedimentation rates, and that the Routt-Divide Blowdown of 1997 did not increase the rates. Based on further evaluation of the sites and the event it appears that slope characteristics and treefall orientation may be significant factors controlling the amount and type of disturbed sediment that moves downslope. In the case of future large-scale blowdowns, where their effect on water quality or sedimentation rates is in question, dominant treefall orientation with respect to slope should be an integral part of initial assessment, especially in remote area, and be considered when interpreting data from any similar study.

Spatial and temporal information on catchment sediment sources and sinks can provide an improved understanding of catchment response to human-induced disturbances. This is essential for the implementation of well-targeted catchment-management decisions. This thesis investigates the nature and timing of catchment response to human activities by examining changes in sediment sources and sinks in a dry-tropical subcatchment of the Great Barrier Reef (GBR) catchment area, in northeastern Australia. Changes in catchment sediment sources, both in terms of spatial provenance and erosion type, are determined using sediment tracing techniques. Results indicate that changes in sediment source contributions over the last 250 years can be linked directly to changes in catchment land use. Sheetwash and rill erosion from cultivated land (40-60%) and channel erosion from grazed areas (30-80%) currently contribute most sediment to the river system. Channel erosion, on a basin-wide scale, appears to be more important than previously considered in this region of Australia. Optically stimulated luminescence and 137Cs dating are used to determine pre-and post- European settlement (ca. 1850) alluvial sedimentation rates. The limitations of using 137Cs as a floodplain sediment dating tool in a low fallout environment, dominated by sediment derived from channel and cultivation sources, are identified. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times) are attributed to the naturally high sediment loads in the dry-tropics. These low increases suggest that previous predictions which reflect order of magnitude increases in post-disturbance sediment yields are likely to be overestimates. In-channel bench deposits, formed since European settlement, are common features that appear to be important stores of recently eroded material. The spatially distributed erosion/sediment yield model SedNet is applied, both with generic input parameters and locally-derived data. Outputs are evaluated against available empirically-derived data. The results suggest that previous model estimates using generic input parameters overestimate post-disturbance and underestimate predisturbance sediment yields, exaggerating the impact of European catchment disturbance. This is likely to have important implications for both local-scale and catchment-wide management scenarios in the GBR region. Suggestions for future study and the collection of important empirical data to enable more accurate model performance are made.

La connaissance de la dynamique hydrosédimentaire des rivières avant et pendant l’installation des nombreux aménagements hydrauliques depuis l’Antiquité restaient très fragmentaire en Basse-Normandie et plus largement en Europe de l’Ouest. On savait encore peu de choses sur les processus d’érosion et de sédimentation qui se sont succédés au sein des rivières normandes au cours des deux derniers millénaires et la part des forçages anthropiques et climatiques qui ont influencé ces processus. L’objectif de la thèse est donc de comprendre et de mesurer la part des héritages dans le fonctionnement actuel des rivières afin de contribuer à leur gestion contemporaine. A cette fin, des recherches géomorphologiques et géoarchéologiques ont été menées dans plusieurs vallées bas-normandes. Ces études ont mis en évidence le poids des installations hydrauliques et en particulier le développement des moulins à eau dans la modification des chenaux d’écoulement mais aussi la construction des plaines alluviales. En effet, la structuration complète du cours d’eau depuis le Moyen Âge a fortement artificialisé les formes en plan et les pentes des cours d’eau et complètement cloisonné leur linéaire. Ces transformations ont favorisé la stabilité latérale des cours d’eau et la sédimentation limoneuse par débordement au sein des plaines alluviales. L’installation de moulins s’accompagne très souvent d’une simplification du tracé en plan de la rivière. Lors de l’équipement maximal des cours d’eau normands on trouvait un moulin tous les 2500 mètres de linéaires hydrographiques. Ces transformations signifient qu’une grande partie des cours actuels sont artificiels. En effet, ces aménagements et l’accélération de la sédimentation limoneuse depuis 1000 ans sont à l’origine de la mise en place d’un équilibre dynamique aboutissant aux formes hydrosédimentaires des rivières actuelles. L’abandon de la gestion des ouvrages hydrauliques et leur destruction au cours des cinquante dernières années viennent remettre en cause cet équilibre
In Lower Normandy, knowledge of the hydrosedimentary dynamics of rivers before and during the installation of the numerous hydraulic installations since the Roman period remains very fragmentary. Little was known about the rates of erosion and sedimentation that have occurred over the last two millennia and how climatic and anthropogenic controls have influenced these processes. Thus, the challenge of this phD is to understand and measure the role of the inherited structures and operating in the current functioning of the rivers of Lower Normandy in order to help with their contemporary management. To provide answers, geomorphological and geoarchaeological researches has been carried out in several valleys. These studies make it possible to highlight the weight of the hydraulic installations and in particular the developments related to the mills in the setting up of floodplains. Indeed, the complete structuring and management of the watercourse since the Middle Ages artificialized riverbed forms and slopes, and partitioned rivers favoring lateral stability and overflow sedimentation in the floodplain conducting in the development of completely regulated rivers. The installation of mills is accompanied locally by a simplification of the river course. At the acme of the equipment there was a mill every 2,500 meters along the rivers of Lower Normandy. These transformations mean that a large part of current courses are artificial. These structures and the increase of the overbank silt sedimentation for 1000 years are at the origin of the establishment of a dynamic equilibrium resulting in the hydrosedimentary forms of the present rivers which are largely inherited. The abandonment of the management of the hydraulic structures and their destruction during the last fifty years comes to question this balance

O presente trabalho teve como objetivo a caraterização química e morfológica de aerossóis atmosféricos de Évora, Alentejo, Portugal e relacioná-los com as suas origens e fontes. A amostragem do material particulado foi efetuada na plataforma observatória do Centro de Geofísica da Universidade de Évora, através de dois tipos de amostragem: “Cascade Impactor” e bomba de vácuo de grande volume, durante dois meses (08-2011/ 02-2012) e “Sedimentation”, durante 8 meses (08-2011 a 03-2012). A caraterização química e morfológica das partículas inorgânicas de aerossóis foi realizada por SEM-EDS e permitiu realizar um sistema de classificação química das partículas, identificandose maioritariamente Desert Dust, Sea Salts, Ca-Rich, Fe-Rich, Mixtures e Sulphates. As retrotrajetórias (HYSPLIT model) atmosféricas permitiram averiguar acerca das origens das partículas (Desert Dusts do Sahara). Na fração orgânica foram identificados PAH’s por GC-MS. Os principais PAH’s encontrados foram o acenaftileno, acenafteno e naftaleno, considerados menos problemáticos para o ambiente; ### ABSTRACT: Aim of the study was the chemical and morphological characterization and source apportionment of PM aerosols in Evora. Sampling was carried at the station of the Evora Geophysics Centre of Evora using two types of protocols. a) Cascade Impactor: particles were collected on TEM grids for two months (08-2011/02-2012; b) Sedimentation mode: particles were collected using a modified version of the aerosol passive sampler Type A. Filters were analyzed by VP SEM-EDS to obtain morphological and elemental chemical data for the inorganic fraction and by GC-MS for the organic fraction. SEM+EDS analysis allowed the classification of the aerosols into different classes of which Desert Dust, Sea-Salt, Ca-rich, Fe-rich, Mixtures and Sulphates were the most abundant. Back Wind Trajectories (HYSPLIT model) confirmed Saharian Dust as the main aerosol source. Within the organic fraction, the GC-MS study identified PAH (Acenaphthylene, Acenaphthene, Naphthalene) which were not considered to represent a major environmental threat.

Nowadays the sediment becomes one significant problem to reservoir watershed and it is effect and related to reservoir operation system. As the research topic, an integrated sediment approach and impacts of climate change on reservoir sedimentation, there are three main parts demonstrated in this research that all parts are related together with sediment point of view. Annual sediment depositing volume in reservoir was estimated by general soil loss equation but the efficiency was not acceptable. The first part of this study shows that the efficiency is improved by using general soil loss equation with sediment transport model. The second part is about monitoring the sediment inflow to reservoir. The important parameter to operate the reservoir is turbidity concentration of flow into dam, in the second part the suspended sediment concentration was predicted by real time therefore the reservoir operation to release turbid flow will get more efficiency. For last part, in the next future year sediment yield and water resources on the study area were investigated by extrapolated temperature and rainfall data then the results will be useful for long term reservoir operation system. First part, the integrated sedimentation was used to model an annual depositing sediment volume in reservoir. Sediment system in watershed includes not only sediment yield but also sediment transportation along the rivers. In this study, the Geographic Information System (GIS) incorporated with sediment yield model can be assisted to enhance the evaluation estimation of soil erosion. Surface erosion on Managawa river basin is then computed with the Modified Universal Soil Loss Equation (MUSLE) and it is verified to reflect the hydrological processes to which it will be able to estimate soil losses. In the sediment transport routing module, total load equation is applied to carry sediment from soil surface erosion to deposit in Managawa dam. According to annual accumulation sediment volume data in Managawa reservoir during 1981 – 2004, the establish model and simulation results are satisfied. The efficiency of the Modified Universal Equation with sediment routing in rivers is more than the simple Modified Universal Equation. Second part, the real time suspended sediment concentration forecasting was used for monitoring the turbidity flow on the upstream of reservoir. The sediment flow into the reservoir is a factor for decision support in real time reservoir operation therefore the serious area of sediment erosion of Managawa river basin, Japan is monitored by suspended sediment gauge. The hourly suspended sediment concentration at Okumotani station; the upstream of Managawa reservoir, was monitored and estimated by the artificial neural network (ANN) model that the input data were rainfall data and its products. This artificial neural network (ANN) was calibrated and validated by using recently suspended sediment data on heavy rainfall events from December 2006 to January 2008. Choosing an appropriate neural network structure and providing field data to that network for training purpose are address by using a constructive back propagation algorithm. Rainfall and its products; the computed discharge from rainfall runoff model and rainfall intensity, were applied as inputs to neural network. It is demonstrated that the artificial neural network (ANN) is capable of modeling the hourly suspended sediment concentration with good accuracy and the neural network model has efficiency more than the multiple linear regression (MLR) model and the sediment rating curve (SRC) model. Last part, the effects of climate change on water resources and sediment yield were investigated by climate change scenarios which the main meteorological data were rainfall and temperature data. Historic trends of temperature and precipitation on Managawa river basin were detected by parametric and nonparametric tests. The daily mean temperature data from 1981 to 2008 at Ono station, Fukui prefecture was the representative of temperature on the study area. The hourly rainfall data from 1981 to 2008 were obtained by Managawa dam office processed with the reliability of data and weighted data. From monotonic and step trend tests, the temperature trend was found herein to follow a clear and steady trend every month. The average annual temperature exhibited an increasing trend with a magnitude 0.4 ºC per decade. Application of the Mann-Kendall and Mann-Whitney test for rainfall time series on Managawa river basin showed no step change and no monotonic trend in Managawa precipitation. The average annual precipitation exhibited a decreasing trend with a magnitude 52 mm per decade. The weather generating models both temperature and rainfall expressed the high efficiency for validation step. The generated weather series 2009 - 2060; temperature and precipitation height, for future climatic conditions can be inputted into the soil loss equation to investigate the change in sediment sources and extrapolated rainfall can be inputted to rainfall runoff model to investigate the change in runoff for future climate change condition. The sediment yield rate should be reduced because of the decrease in precipitation.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第14934号
工博第3161号
新制||工||1474(附属図書館)
27372
UT51-2009-M848
京都大学大学院工学研究科社会基盤工学専攻
(主査)教授 角 哲也, 教授 田村 武, 教授 藤田 正治
学位規則第4条第1項該当

The Ceratium species occurring in the Vaal River since 2000, was identified as Ceratium hirundinella (O.F. Müller) Dujardin as proposed by Van Ginkel et al (2001). Ceratium hirundinella is known to cause problems in drinking water purification and has been penetrating into the final drinking water of Rand Water since 2006. Ceratium hirundinella is associated with many other water purification problems such as disrupting of the coagulation and flocculation processes, blocking of sand filters and algal penetration into the drinking water. Ceratium hirundinella also produce fishy taste and odorous compounds and causes discolouration of the water. The aims of this study were to determine the main environmental factors which are associated with the bloom formation of C. hirundinella in the source water and to investigate the influence of C. hirundinella on the production of potable water. In order to optimise treatment processes and resolve problems associated with high C. hirundinella concentrations during the production of potable water, jar testing and chlorine exposure experiments were performed. Multivariate statistical analyses were performed to determine the main environmental variables behind C. hirundinella blooms. Ten years data (2000 - 2009) from the sampling point C–VRB5T in the Vaal River, (5 km upstream from the Barrage weir) were used for this investigation, because C. hirundinella occurred there frequently during the ten year period. In this study, it was found that C. hirundinella was favoured by high pH, Chemical Oxygen Demand (COD), orthophoshapte (PO4), and silica concentrations, as well as low turbidity and low dissolved inorganic nitrogen (DIN) concentrations. No correlation was found between C. hirundinella and temperature, suggesting that this alga does not occur during periods of extreme warm or extreme cold conditions, but most probably during autumn and spring. The results of the multivariate statistical analysis performed with historical data from Vaalkop dam, indicate that the dinoflagellate C. hirundinella seems to be favoured by low temperature and turbidity, and high DIN, Fe, Methyl–orange alkalinity, Cd, PO4, Conductivity, pH, hardness and SO4 concentrations. In order to optimise treatment processes such as coagulation, flocculation and sedimentation, jar testing experiments were performed to investigate different coagulant chemicals namely: cationic poly–electrolyte only, cationic poly–electrolyte in combination with slaked lime (CaO) and CaO in combination with activated silica. Water from four different sampling localities were chosen to perform the different jar testing experiments: 1) sampling point M–FOREBAY (in the Forebay, connecting the canal to the Zuikerbosch Purification plant) near Vereeniging due to its proximity to the Zuikerbosch treatment plant, 2) M–CANAL_VD (upstream from the inflow of the recovered water from Panfontein) to determine the influence of (if any) the recovered water from Panfontein on Forebay source water, 3) source water from Vaalkop Dam (M–RAW_VAALKOP) and 4) source water from Rietvlei Dam (water from both Vaalkop and Rietvlei Dams contained high concentrations of C. hirundinella at that time of sampling) to determine which coagulant chemical is the most effective in removing high concentrations of C. hirundinella cells during the production of drinking water. The jar testing experiments with Vaalkop Dam and Rietvlei Dam source water (rich with C. hirundinella) indicated that using cationic poly–electrolyte alone did not remove high concentrations of C. hirundinella efficiently. However, when CaO (in combination with cationic poly–electrolyte or activated silica) were dosed to Vaalkop Dam source water a significant decrease of C. hirundinella concentration was observed. This indicates that the C. hirundinella cells were “shocked or stressed” when exposed to the high pH of the CaO, rendering it immobile and thereby enhancing the coagulation and flocculation process. However, when 10 mg/L CaO in combination with poly–electrolyte was dosed to Rietvlei Dam source water the turbidity and chlorophyll–665 results indicated that this coagulant chemical procedure was ineffective in removing algal material from the source water. The jar testing experiments using the cationic poly–electrolyte alone or cationic poly–electrolyte in combination with CaO on M–FOREBAY and M–CANAL_VD source water, showed a decrease in turbidity, chlorophyll–665 concentration, and total algal biomass, with an increase of coagulant chemical. When CaO in combination with activated silica was dosed, the inherent turbidity of the lime increased the turbidity of the Vaalkop Dam, M–FOREBAY and M–CANAL_VD source water to such an extent that it affected coagulation negatively, resulting in high turbidity values in the supernatant. Regardless of the turbidity values, the chlorophyll–665 concentration and total algal biomass (C. hirundinella specifically in Vaalkop Dam source water) decreased significantly when CaO was dosed in combination with activated silica. Therefore it was concluded that a cationic poly–electrolyte alone is a good coagulant chemical for the removal of turbidity, but when high algal biomass occur in the source water it is essential to add CaO to “stress” or “shock” the algae for the effective removal thereof. However, when CaO in combination with activated silica was dosed to Rietvlei Dam source water a decrease in turbidity and chlorophyll–665 concentration was found with an increasing coagulant chemical concentration. These results confirm the fact that coagulant chemicals may perform differently during different periods of the year when water chemistry changes and that certain coagulant chemicals may never be suitable to use for certain source waters. For the effective removal of algae during water purification, it is recommended that cationic poly–electrolyte in combination with CaO are used as coagulant chemical at the Zuikerbosch Water Purification Plant. Turbidity is not a good indication of algal removal efficiency during jar testing experiments. If problems with high algal concentrations in the source water are experienced it is advisable to also determine the chlorophyll–665 concentrations of the supernatant water during the regular jar testing experiments, since it will give a better indication of algal removal. Chlorine exposure experiments were performed on water from Vaalkop Dam (M–RAW_VAALKOP) and Rietvlei Dam source water, to determine the possibility of implementing pre– or intermediate chlorination with the aim to render the cells immobile for more effective coagulation. The chlorine exposure experiments with Vaalkop Dam and Rietvlei Dam source water showed similar results. The chlorine concentration to be dosed as part of pre– or intermediate chlorination will differ for each type of source water as the chemical and biological composition of each water body are unique. When the effect of chlorine on the freshwater dinoflagellate C. hirundinella was investigated, it was found that the effective chlorine concentration where 50 % of Ceratium cells were rendered immobile (EC50) was approximately 1.16 mg/L for Vaalkop Dam source water. For the source water sampled from Rietvlei Dam, it was found that the EC50 was at approximately 0.87 mg/L. Results of analyses to determine the organic compounds in the water after chlorination revealed that an increase in chlorine concentration resulted in increase in total organic carbon concentration (TOC), as well as a slight increase in MIB and trihalomethanes (CHCl3). Pre– or intermediate chlorination seem to be an effective treatment option for the dinoflagellate C. hirundinella to be rendered immobile and thereby assisting in its coagulation process. The use of pre– or intermediate chlorination to effectively treat source waters containing high concentrations of C. hirundinella is a viable option to consider. However, the organic compounds in the water should be monitored and the EC50 value for each source water composition should be determined carefully as to restrict cell lysis and subsequent release of organic compounds into the water.
Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2012.

The excessive deposition of fine inorganic sediment (<2 mm) is a major pathway by which agricultural land uses exert pressure on stream ecosystems. However, less well understood are the underlying mechanisms driving threshold biotic responses and the ecological consequences of community changes to sedimentation. Reviewing the literature, I found that sedimentation can affect algal and detrital pathways, and invertebrate community composition may show abrupt shifts with increased sediment. Moreover, functional changes to communities potentially leads to simpler food webs, with altered interactions and decreased ecosystem function. After identifying these knowledge gaps, I conducted survey and experimental research using agricultural streams on the Canterbury Plains of New Zealand’s South Island. Results from my survey of 30 streams along a sedimentation gradient showed that pollution-sensitive invertebrates (% EPT; Ephemeroptera, Plecoptera, Trichoptera) demonstrated threshold responses to sediment that varied with spatial scale, and change-point analysis indicated marked declines beyond 20% fine sediment covering streambed reaches. Structural equation modeling indicated that decreased habitat availability was a key mechanism contributing to these changes. To better understand the functional consequences of altered community structure, I investigated food webs in 12 streams along the gradient. The results showed a compression of community trophic niche space, suggesting that in particular, primary consumers became trophically more equivalent. The simplification of stream food webs with increasing sediment appeared to be the result of functional changes to invertebrate communities, with fewer specialised consumers, and shifts in the availability of basal resources. Using field and laboratory experiments investigating litter breakdown and invertebrate feeding, I found that the net consequence of functionally less diverse stream communities with increased sediment was impaired ecosystem function, demonstrated by a reduction in litter breakdown rates. The reduction of detrital resource availability through burial by sediment in laboratory mesocosm experiments strongly influenced detrital consumption rates, thus leading to reduced growth and survival of detritivorous caddisflies. The survey and experimental results support my postulate that sediment deposition causes environmental stress by degrading benthic habitat and making associated food resources (e.g., periphyton and leaves) less available. Overall, my results have provided new insights into sediment impacts on stream communities and have furthered our understanding of how these changes affect the structure and functioning of stream ecosystems.

Road construction and maintenance throughout the country continues to be one of the largest contributors of sediment pollution to aquatic systems. Though impacts of road networks on aquatic systems can be potentially severe, little work has been performed to evaluate the effect that road spatial location within a watershed has on water quality. To address this issue from a quantitative perspective, a â Road Impact Factorâ protocol was designed to identify potential erosion-prone segments of road networks based on road gradient, spatial location based on hydrologic flow length, surface composition, and water control installations. The protocol was developed for two regions in Central Idaho and Eastern Oregon. We then used the hydrologic travel time procedure, developed for use in the Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) runoff and routing model, in order to characterize the spatial distribution of potential road runoff impacts within the study areas. Ten macroinvertebrate metrics sensitive to sedimentation (i.e. % Intolerant Taxa, Hilsenhoff Biotic Index, etc.) were analyzed to test the significance of the spatial distribution of Road Impact Factors. These 10 metrics were analyzed under the hypothesis that values will be lower for those study areas that have a higher degree of road impact and a lower distance between the road segments and stream reaches. Results of a quadrant analysis and hierarchical clustering analysis showed hypothesized trends for several metrics in Idaho, though the trends were not strong. No trends were observed in Oregon. The variability in results is likely due to limitations of the input datasets.
Master of Science

Alluvial streams re-shape their own geometry in response to changes imposed by nature or by humanity. Such adjustments may induce landscape and water surface elevations that are not compatible with the natural environment or existing activities. Therefore, for the purpose of planning, design and management, it is necessary to evaluate the variation of the levels, their effect on water and sediment movement and their general impacts to project developments. Both fieldwork and modelling techniques have been developed for assessing the hydrological impacts of such changes. In-stream sand quarry pits on alluvial rivers provide classic examples where streambed elevations are significantly affected by sedimentation changes, which occur concurrently with variation of water surface elevations. The hydrological impacts of a sand mining location on the River Kibos in Kenya are demonstrated by the aid of a simple improvised technique based on rating curve analysis, showing, for example, that due to sand mining the river bed and the corresponding low flow levels fell by about 0.8 m between 1977 and 1982. Noting the desire to make such assessments in advance so as to avoid the repair costs, a modelling procedure has been developed to enable a priori assessments. The dynamic equations describing the one-dimensional open-channel water and sediment flows, and the equation for the two-dimensional transient groundwater flow are solved simultaneously, and linked through a time-dependent interface boundary layer between the alluvial stream-aquifer systems. Considering the scarcity and uncertainty of data sets in this subject, the model has been applied to conceptual hydrologic systems to delineate interrelationships among individual hydrologic components as well as to determine the degree of influence of various parameters on the system behaviour Results by numerical experiments have suggested that baseflow recession curves for aggrading channels deviate steeply from the theoretical logarithmic recession curve as the river becomes more and more influent, while in a degrading reach the baseflow recession curves flatten, deviating from the theoretical recession curve as the river becomes more and more effluent. The hydrologic and fluvial impacts of in-stream sand borrow pit schemes have also been analysed. On the basis of some set-up options, the model allows for realistic predictions of changes to the water and sediment yields, and for the final selection of quarry schemes with least negative impact on the environment.

Yes
This study investigated the impact of sedimentation on rainwater storage system using a case study at the Ikorodu area of Lagos state, a rural area in Nigeria. In this investigation, the proportions of Escherichia coli (E. coli) that were settleable (due to sedimentation) and those that were at the free phase have been studied. Water samples were collected from different depths in the inspected rainwater storage tank at two different periods (i.e. rainy and dry periods) for 20 days. The samples collected from these periods have been analysed for physical and microbial measures before passing it through the serial filters with pore sizes of 500 μm, 100 μm, 10 μm and 1.5 μm to measure the retained particle mass. From the results, it was observed that: (1) the water quality at the free-phase zone was better than that at the tank’s bottom; (2) the settleable bacteria rapidly sinked to bottom; (3) the correlation of turbidity, E. coli and total suspended solids (TSS) for all the rain events showed a relatively high Pearson’s coefficient of 0.9 to one another; and (4) over 70% of settling TSS occurred within first 36 hours. Finally, it has been found that the physical sedimentation process can significantly reduce the microbial measures.

Understanding sedimentation impacts to benthic macroinvertebrates in headwater, mountain streams is a top priority of watershed management programs in the Chattahoochee National Forest. Five studies involving the analysis of historical, biological survey data and current data were conducted to improve our understanding of macroinvertebrate response to sedimentation and to support the development of biological information for sediment load models to be applied in the Chattooga River watershed. An initial analysis of historical data involving a composited, macroinvertebrate reach-scale sample revealed weak relationships between assemblage metrics and sedimentation, which was similar to results of two recent macroinvertebrate studies that found biological ratings of good or excellent with reported physical impact attributed to sedimentation. Those findings and field reconnaissance in the Chattooga River watershed revealed that patchy, coarse sands may be the primary issue of concern regarding sedimentation impact to benthic macroinvertebrates. Therefore, a modified sampling approach was used to investigate relationships of macroinvertebrates and environmental conditions that included micro-habitat patches containing coarse sands, a product of erosion associated with Southern Blue Ridge, silicate parent geology. At the microhabitat, patch scale, flow velocity was the main environmental factor associated with a macroinvertebrate assemblage gradient, and was significantly correlated with percent deposited sediment across 264 samples. The high dominance of just a few macroinvertebrate genera, and the majority lack of individual macroinvertebrate associations with dominant substrate types may suggest that the dominant macroinvertebrates utilize a multi-microhabitat portion of the streambed at any given time, which may be due to the homogenization of streambeds due to sand (providing ease of movement) and its immobility (low bedload volume and sand patch shift). Because flow was the only significantly correlated environmental variable on an assemblage gradient produced by ordination (and was individually correlated with dominant substrate and percent deposited sediment), a subsequent study was conducted to determine macroinvertebrate sensitivity to deposited sediments among two flow-differentiated habitat types. Results showed that more taxa were related to a gradient of percent deposited sediment in fast water habitats, and no taxa were positively correlated with percent deposited sediment. Indicator species analysis found a number of taxa that were associated with a four-level grouping of percent deposited sediment levels. Therefore, a final study involved calculating deposited sediment tolerance values using indicator species associations and individual cumulative abundances across percent deposited sediment levels. The final index developed from cumulative abundances showed a relationship with deposited sediment within the range 0 â 30%, and that low range was due to the low deposited sediment levels at which all 50% cumulative abundances fell (1 - 10%). The sedimentation index produced from indicator species analysis produced a reach-scale index that was related to percent pool embeddedness. Key findings from these studies are: (1) sand is the primary deposited sediment type, with most streambed comprised of cobble-sand substrate, (2) few taxa are associated with deposited sand substrate, (3) there are high numbers of a relatively few dominant taxa across samples and streams, (4) macroinvertebrate response to deposited sediments is greatest in fast water habitats, and (5) the developed sedimentation biotic index is a potential, assemblage-level indicator of increasing sedimentation in these headwater systems. The functional and habit organization of the four most dominant taxa determined in recent studies suggest that they may be utilizing sand patches for crawling and collecting food, therefore structurally adapting to long-term, press disturbances due to historical and contemporary anthropogenic activities and natural erosion. In addition, macroinvertebrate assemblage composition in these streams indicates overall good â healthâ and suggests streambed stability in the presence of a large portion of coarse sand. However, an important question that remains involves sand movement along streambeds and the ecological consequences of continued sediment inputs to these headwater systems.
Ph. D.

Thesis (Ph. D.)--West Virginia University, 2008.
Title from document title page. Document formatted into pages; contains xii, 162 p. : ill. (some col.), maps (some col.). Vita. Includes abstract. Includes bibliographical references.

La pesca d’arrossegament és considerada una de les activitats antròpiques més nocives pel medi marí, degut a la seva extensió global, i l’elevada freqüència i intensitat. Com que aquest art està en contacte continu amb el fons marí, pot modificar la morfologia del fons i resuspendre grans volums de sediment, que poden ser advectats, erosionant els caladors i alterant les propietats del sediment. Amb la expansió global de la pesca d’arrossegament a caladors més profunds des dels anys 1950, s’estima que els impactes ocasionats per aquesta activitat poden ser intensificats, però encara hi ha una manca d’estudis d’aquests. L’objectiu d’aquesta tesi era estudiar els impactes físics i biogeoquímics de la pesca d’arrossegament profunda al marge occidental Mediterrani. Els impactes físics es van estudiar als canyons submarins catalans mitjançant l’anàlisi de més de 30 testimonis de sediment dels flancs i eixos dels sis canyons més importants de la costa. Aquest estudi va observar que els caladors, als flancs dels canyons, estaven erosionats, i aquest sediment és desplaçat als eixos dels canyons, duplicant i quadruplicant els ritmes de sedimentació degut a la expansió dels caladors a ambients més profunds als anys 1960 i 1970. Aquest impacte només s’observa en zones properes als caladors, i els ritmes de sedimentació induïts per la pesca disminueixen a major distància dels caladors. Un segon augment en el ritme de sedimentació va ser identificat en un dels canyons al principi dels 2000 degut a una modernització recent de la flota d’arrossegament, ressaltant la relació entre la tecnificació de la flota i les alteracions en els règims sedimentaris. Aquestes alteracions físiques del fons marí també modifiquen la biogeoquímica dels caladors, disminuint el contingut de matèria orgànica. Al Golf de Castellammare (Sicília), l’acumulació de matèria orgànica fresca i nutritiva en un calador erosionat i empobrit en nutrients (20-60 % menys matèria orgànica) va estimular la resposta microbiana. Tot i això, la elevada freqüència dels vaixells d’arrossegament ràpidament erosiona aquest sediment recent, inhibint la recuperació dels caladors del Golf de Castellammare. Aquest fet ens va suggerir que èpoques de veda podrien mitigar els impactes de la pesca d’arrossegament. No obstant, la comparació de testimonis de sediment agafats en diferents èpoques, incloent al final d’una veda de 2 mesos, als caladors del canyó de Palamós va demostrar que aquesta estratègia és insuficient per mitigar els impactes de la pesca d’arrossegament. El contingut de matèria orgànica als caladors estaven especialment empobrits en els compostos més làbils (52-70 % menys), perjudicant la preservació de matèria orgànica als sediments profunds i reduint la qualitat nutritiva dels caladors, el qual podria tenir impactes transcendentals a les comunitats bentòniques, incloent les espècies comercials. Aquests impactes van persistir durant totes les èpoques de mostreig, fins i tot després de la veda, degut als baixos ritmes de sedimentació en aquesta zona. Aquests resultats ressalten la vulnerabilitat i baixa resiliència d’ambients profunds, i recalca que la pesca d’arrossegament profunda perjudica la integritat dels fons marí més enllà de la seva capacitat de recuperació. Considerant l’expansió global dels caladors de pesca d’arrossegament, aquests impactes podrien ocórrer en talussos continentals a escala global.
La pesca de arrastre es considerada una de las actividades antrópicas más nocivas para el medio marino, debido a su extensión global, y la elevada frecuencia e intensidad. Puesto que este arte de pesca está en contacte continuo con el fondo marino, puede modificar la morfología del fondo y resuspender grandes volúmenes de sedimento, que pueden ser advectados, erosionando los caladeros y alterando las propiedades del sedimento. Con la expansión global de la pesca de arrastre a caladeros más profundos desde los años 1950, se estima que los impactos ocasionados por esta actividad pueden ser intensificados, pero todavía hay una falta de estudios. El objetivo de esta tesis era estudiar los impactos físicos y biogeoquímicos de la pesca de arrastre profunda en el margen occidental Mediterráneo. Los impactos físicos se estudiaron en los cañones submarinos catalanes mediante el análisis de más de 30 testimonios de sedimento de los flancos y ejes de los seis cañones más importantes de la costa. Este estudio observó que los caladeros, en los flancos de los cañones, estaban erosionados, y este sedimento es desplazado a los ejes de los cañones, duplicando y cuadriplicando los ritmos de sedimentación debido a la expansión de los caladeros a ambientes más profundos en los años 1960 y 1970. Este impacto sólo se observó en zonas próximas a los caladeros, y los ritmos de sedimentación inducidos por la pesca disminuyen a mayor distancia de los caladeros. Un segundo aumento en el ritmo de sedimentación fue identificado en uno de los cañones a principio de los 2000 debido a una modernización reciente de la flota de arrastre, resaltando la relación entre la tecnificación de la flota y las alteraciones en los regímenes sedimentarios. Estas alteraciones físicas en el fondo marino también modifican la biogeoquímica de los caladeros, disminuyendo su contenido de materia orgánica. En el Golfo de Castellammare (Sicilia), la acumulación de materia orgánica fresca y nutritiva en un caladero erosionado y empobrecido en nutrientes (20-60 % menos materia orgánica) estimuló la respuesta microbiana. A pesar de esto, la elevada frecuencia de los barcos de arrastre rápidamente erosiona este sedimento reciente, inhibiendo la recuperación de los caladeros del Golfo de Castellammare. Este hecho nos sugirió que épocas de veda podrían mitigar los impactos de la pesca de arrastre. No obstante, la comparación de testimonios de sedimento recuperados en diferentes épocas, incluyendo al final de una veda de 2 meses, en los caladeros del cañón de Palamós demostró que esta estrategia de gestión es insuficiente para mitigar los impactos de la pesca de arrastre. El contenido de materia orgánica en los caladeros estaba especialmente empobrecido en los compuestos más lábiles (52-70 % menor), perjudicando la preservación de materia orgánica en los sedimentos profundos y reduciendo la calidad nutritiva de los caladeros, lo cual podría tener impactos transcendentales en las comunidades bentónicas, incluyendo las especies comerciales. Estos impactos persistieron en todas las épocas de muestreo, incluso después de la veda, debido a los bajos ritmos de sedimentación en esta zona. Estos resultados resaltan la vulnerabilidad y baja resiliencia de ambientes profundos, y recalca que la pesca de arrastre profunda perjudica la integridad del fondo marino más allá de su capacidad de recuperación. Considerando la expansión global de los caladeros de pesca de arrastre, estos impactos podrían ocurrir en taludes continentales a escala global.
Bottom trawling is considered one of the most harmful anthropogenic activities in the marine environment given its widespread occurrence, high frequency, and intensity. Since bottom trawling gear are in continuous contact with the seafloor, it can modify seabed morphology by erasing natural sedimentary structures and resuspend large volumes of sediment, which can be advected from trawling grounds, eroding the seafloor and altering sediment properties. With the global expansion of bottom trawling to deeper fishing grounds since the mid-XXst century, it is expected that the impacts caused by this activity will be intensified, but studies assessing them are still scarce. The aim of this thesis was to study the physical and biogeochemical impacts of deep bottom trawling in the Western Mediterranean margin. The physical impact of bottom trawling in submarine canyons of the Catalan margin was studied through the analyses of over 30 sediment cores collected in canyon flanks and axes of six major submarine canyons incising the continental slope. This study observed that trawling grounds located along the canyon flanks are highly eroded, and this sediment is displaced towards the canyon axis, leading to a two- to four-fold increase in sedimentation rates in their axes since the expansion of bottom trawling grounds to deeper environments during the 1960s and 1970s. Trawling-enhanced sedimentation in these canyons are limited to areas located next to bottom trawling grounds, and trawling-derived sedimentation rates decrease towards the lower canyon axis with greater distance from bottom trawling grounds, leaving deeper areas unaffected. A second increase in sedimentation rates was observed in one of the canyons in the early XXIst century derived from the recent modernization of bottom trawling fleets, highlighting the clear interrelation between fleet technification and the modification of sedimentary regimes. These continuous physical alterations can also modify the biogeochemistry of deep bottom trawling grounds, depleting sedimentary organic matter. In the Gulf of Castellammare (Sícily), the accumulation of fresh and nutritionally rich organic matter in nutrient-deprived (20-60 % less organic matter) and eroded deep bottom trawling stimulated the microbial response, causing high turnover rates of labile organic matter. However, the high trawling frequency quickly erodes freshly-accumulated sediment, inhibiting the recovery of fishing grounds in the Gulf of Castellammare. This initially suggested that temporal trawling closures could mitigate the impacts of bottom trawling. However, the comparison of sediment cores collected during several seasons, including towards the end of a 2-month trawling closure in fishing grounds of Palamós Canyon revealed that this management strategy is insufficient to mitigate the impacts of bottom trawling. Organic matter in the trawled site was especially impoverished in the most labile biomarkers (52-70 % loss), hampering the preservation of organic matter in deep-sea sediments and diminishing the nutritional quality on trawling grounds, which could have transcendental impacts on benthic communities, including the targeted commercial species. These impacts persisted in every sampling season, even after the temporal trawling closure, since the low sedimentation rates of the area is not capable of restoring these fishing grounds. These results highlight the vulnerability and low resiliency of deep-sea environments, and stresses that deep-sea trawling damages the seafloor's integrity beyond repair. Considering the global expansion of bottom trawling grounds, these impacts could be occurring in trawled continental slopes worldwide.

Java, l'île principale de l'archipel indonésien a vu la construction, depuis les années 1960, de nombreux grands barrages. Leurs rôles sont multiples, passant du contrôle des flux liquides (écrêtage des crues et soutien des étiages) à l'approvisionnement en eau des grandes agglomérations urbaines et des terres agricoles. Ils jouent également le rôle important de fournisseur d'énergie. Depuis leur mise en eau, on assiste à un comblement rapide des réservoirs liés à des taux d'érosion qui figurent parmi les plus élevés du monde. La diminution importante de leur efficacité entraîne par conséquent de nombreuses répercussions néfastes sur le milieu et les sociétés. Les objectifs de cette recherche sont ainsi de déterminer, avec des approches multiples (SIG, télédétection, base de données hydro-climatiques, sondages lacustres...), les taux et les rythmes de remplissage de ces réservoirs, agissant comme indicateurs de l'érosion dans leur bassins-versants respectifs. Il s'agira de mettre en évidence les facteurs principaux influant sur cette forte sédimentation et de mettre en place des outils permettant de venir en aide aux organismes chargés de la gestion des bassins-versants javanais
Since the Sixties, a large number of dams have been built in the Indonesian archipelago's main island, Java. Their rôle are multiple, going from liquid flows control (flood – peak shaving and low flow support) to water supply of great urban areas and agricultural lands. They also are an important energy supplier. After their watering, a fast filling of the tanks related to rates of erosion that appear among the highest in the world, has been observed. This significant efficiency decrease involves multiple negative impacts on environment and utilities. Through a multiple approach (GIS, remote sensing, hydroclimatic databases, lake surveys...), the objectives of this research are to determine the sedimentary transfer rates and pace within the studied basins, which act as erosion indicators in their respective basins. The key determinants affecting this high sedimentation will be highlighted and a software will be developed with the aim to provide Javanese river basins authorities with new tools

O processo de sedimentação e assoreamento reduz a profundidade e a capacidade dos lagos de armazenamento de água do Canal do Panamá, obrigando a realizar dragagens periódicas que aumentam os custos de operação. Esses processos são acelerados pela perda de cobertura florestal na bacia. O presente estudo teve por objetivo estimar o valor econômico associado à redução de sedimentos na floresta da bacia do Canal, através do método de custo evitado de dragagem. O efeito físico da cobertura florestal sobre a redução de sedimentos foi estimado a través de regressão linear de dados biofísicos de sete microbacias que dispõem de medições de produção de sedimentos: Chagres, Pequení, Boquerón, Gatún, Trinidad, Cirí Grande e Caño Quebrado. Os resultados mostram que cada hectare de floresta nesta área reduz em 14,76 t.ano-1 de sedimentos em suspensão. Adicionando sedimentos de fundo isso corresponde a 14,32 t.ha-1.ano-1 e a um valor econômico de USD 197,40 por hectare por ano. Concluiu-se que as florestas contribuem significativamente para mitigar o processo de assoreamento dos lagos de armazenamento de água para o funcionamento do Canal do Panamá, e essa contribuição pode ser valorada em USD 39.640.091 por ano, para toda a floresta da bacia.
Sedimentation and siltation reduce the lakes depth and capacity to hold water in the Panama Canal, requiring periodic dredging which increases the operation costs. These processes are accelerated by the loss of forests that cover the basin. This studys objective is to estimate the economic value associated with reduction of sediments in the Canal basin, based on the method of avoided dredging cost. The physical effect of forest on sediment reduction was estimated through linear regression of biophysical data for seven watersheds that have measurements of sediments yield: Chagres, Pequení, Boquerón, Gatún, Trinidad, Cirí Grande and Caño Quebrado. These results shows that each hectare of forest in this area reduces the sediments in suspension. By adding sediments from the bottom of the riverbed, this corresponds to 14.32 m3.ha- 1.year-1 and to an economic value of USD 197.40 per hectare per year. It was concluded that forests contribute significantly to mitigate the process of siltation of lakes water storage for the operation of the Panama Canal, and this contribution may be valued at USD 39,640,091 per year for the entire basin forest.

Tookoonooka and Talundilly are two large meteorite impact structures buried in the sedimentary rocks of central Australia, and are among the largest impact structures known on Earth. They are shown to be a rare example of an ancient marine impact event and are also an extremely rare terrestrial example of a probable binary impact event. A preserved marine impact ejecta horizon, interpreted to span a vast area of the continent and corresponding to the extent of a Cretaceous epicontinental sea, is used to biostratigraphically constrain the impact age to the Barremian-Aptian boundary (125 +/- 1 Ma) in the Lower Cretaceous. Evidence is presented that the Wyandra Sandstone Member petroleum reservoir overlying the horizon is, in part, a binary impact tsunamiite. Analyses of drill core, subsurface drilling data, and geological outcrops over >805,000 km² show that the base of the Wyandra Sandstone Member is an impact horizon: a widespread scour surface that is attributed to impact-related excavation and tsunami scour mechanisms. The impact horizon is underlain by seismites and overlain by very poorly sorted sediment with highly polymictic exotic clasts, imbricated pebbles, and intraformational cobble rip-up clasts. Exotic clasts are predominantly interpreted as impactoclasts, and include complex accretionary and armoured impactoclasts of vapour plume origin, shock-metamorphosed lithic fragments, and altered melt impactoclasts. Some lithic fragments resemble basement lithologies from the Tookoonooka and Talundilly target rock sequences. The stratigraphy of the Wyandra Sandstone Member contains elements characteristic of impact tsunami deposition including ejecta entrained in high flow regime bedforms, pebble to boulder-sized clasts, >16m thick beds, and cyclic sedimentation of tsunami couplets, across five depositional realms. These elements are in stark contrast to the persistently low-energy nature of the ambient sedimentation and overlying quiescent marine shales, but are consistent with the intense seismicity, high energy seiche action and rapid deposition expected from a marine impact in a mostly enclosed basin. A dual impact source is indicated, based on sediment distribution patterns in combination with the proximity of the impact structures in age and location. The Wyandra Sandstone Member records both marine impact depositional processes as well as the waning of the event; the upper part of the Wyandra returns to background depositional energies and intense bioturbation and is conformably overlain by transgressive marine shales. The Tookoonooka-Talundilly impact event may be an extreme prototype, as very few doublet craters, marine craters, impact tsunamiites, or economic impactites are individually known or preserved on Earth, yet this crater pair may represent all four. This impact crater pair provides a model for binary marine impact sedimentation and highlights the significance of ancient impact sediments to petroleum basins. Sedimentation patterns evidence a dual crater source even in a marine impact scenario where reworking and burial complicate the interpretation of depositional indicators; observations suggest that Tookoonooka-Talundilly may be the largest doublet crater discovered on Earth.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, Australian School of Petroleum, 2015.

For certain shellfish species, a mechanical harvester has the potential to greatly reduce harvesting costs. Traditionally, hand rakes are used in shellfish harvesting in British Columbia. In order to determine if it is environmentally feasible to use a mechanical harvester, an environmental assessment on mechanical harvesting and traditional harvesting needs to occur for comparison. In July 2008, a preliminary oceanographic assessment was conducted at three study sites in Baynes Sound. Each of the three study sites contained a mechanical and manual harvest plot and reference stations. Sampling stations were established at fixed positions within each plot and at four positions along a downstream transect (following the dominant current direction.) Surveys were conducted 24 hours pre-harvest, immediately post-harvest, and 24 hours post-harvest. Parameters included in situ sediment sulphides, eH (REDOX), sediment grain size (SGS), visual condition (digital imagery), sedimentation (silt flux) and sediment macro-fauna. Results show only localized environmental effects associated with each harvest approach; with no significant difference documented between the manual and mechanical harvesting methods on the study beaches. These results indicate the use of a mechanical shellfish harvester is as environmentally sound as the traditional method of hand harvesting, and poses no additional environmental risks. Introducing mechanization in shellfish harvesting will allow shellfish producers to reduce costs and increase profits, making the British Columbian shellfish industry more competitive with other suppliers.
Graduate

Christopher Brunner investigated the cumulative impacts of climate change, sedimentation and light attenuation on coral recruits. He found that recruits were twice as sensitive to sediment-induced stress under future climate conditions. His results will be used for revising water-quality management targets in response to a changing climate.

It has long been established that land use disturbances can induce elevated sediment yields in affected drainage basins. This effect is well documented with respect to forestry activities in the Pacific Northwest. A major problem encountered in studying disturbed sediment yields in the Pacific Northwest is putting the forestry impacts in context with the high degree of spatial and temporal variability in the sedimentary system. The analysis of lake sediments is an attractive method for assessing land use impacts on sediment yield at the basin scale, since a long term sedimentary record can be established that reflects all of the integrated upstream watershed effects. In this study, lake sediment records have been utilized to investigate historical sedimentation patterns in Northwestern British Columbia. Core chronologies and sedimentation rates were derived from ²¹³Pb dating techniques. Study catchments have been selected that span a range of spatial scales, physiographic regions, and land use histories, in order to permit a comprehensive regional assessment of lake catchment sediment yield. Study objectives include the assessment of the natural patterns of lake sedimentation, determining the relative impact of forestry on lake sedimentation in context with the naturally observed variability, and the confirmation of lake coring and associated analysis techniques as appropriate methods of assessing land use disturbances. Specific sediment yield, or sediment yield per unit of contributing basin area, is used as an index of primary subareal denudation of the lake catchments. Specific yield in Northwestern British Columbia spans two orders of magnitude, from 0.0015 Mg/km²/day in the Interior Plateau to 0.1434 Mg/km²/day in the North Coast. The higher rates of sediment yield in the North Coast reflects the higher erosion rates, greater transport capacity, and lower storage potential in that region. Specific sediment yield also increases with increasing drainage area in the North Coast. This trend is likely associated with the dominance 6f secondary remobilization of Quaternary sediments from stream banks and valley bottom areas. In the flat-lying plateau and major valley areas specific sediment yield decreases with increasing drainage area, thus fitting the conventional model of sediment delivery where storage efficiency increases downstream. In the Hazelton and Skeena Mountains there is no significant relation between specific yield and drainage area. There is a clear trend towards increasing lacustrine sedimentation rates irrespective of land use change in the lake catchments. This natural trend is a major confounding factor in disentangling land use impacts on sedimentation patterns. This trend may be related to precipitation increases undergone in the whole study area over the last few decades. Natural disturbances, such as mass wasting and other geomorphic events, are important processes of sediment transfer in headwater lake catchments, although specific processes influencing lacustrine sediment yield were undetermined. Superimposed on. all of the observed natural variability are some qualitative and semi-quantitative land use effects on sediment yield. Land use impacts could only be partially separated from natural fluctuations, however, a clear land use signature, in the form of increased sedimentation rates, was observed in some of the study lakes. Most significant recent increases in sedimentation rates have occurred in the Nechako Plateau, Nass Basin and Major Valleys lakes which have been exposed to extensive forestry activities. Lake catchments which have been subject to multiple land use activities also showed a clear land use impact in the sedimentary signatures. Results indicate that lake sediment-based research can be an effective and useful approach to assess the long term impacts of forest harvesting and other land use disturbances on lake catchment yield. Inherent limitations of the lake sediment-based methodology and recommendations for future work are reviewed.

碩士
國立交通大學
環境工程系所
107
Overdosing Al-based coagulants for treating low turbidity raw water has raised concerns about the excessive residual aluminum ions in treated water that could pose a threat to human health. In addition, clogging problem on the filter and the residual color of the treated water frequently occurred when FeCl3 is singly applied. In Taiwan, algogenic organic matter (AOM) in reservoir has always been a critical problem when it enters the treatment process. Intracellular organic matter (IOM) may release from the algal cell lysis during pre-chlorination. The hydrophilicity, low molecular weight (MW) and the protein-like substances of IOM could form soluble complexes with the coagulant and decrease the destabilization performance during the coagulation process. Therefore, this study aimed to clarify mechanism and the performance of IOM removal by different dosing modes including single dosing (e.g., FeCl3 and Alum) and sequence dosing (e.g., Alum→FeCl3 and FeCl3→Alum) under variation of pH. During the jar test, FlocCAM was installed on the jar to monitor the characteristics of floc. Supernatant was sampled for the analysis of dissolved organic carbon (DOC) to evaluate the separation performance of the IOM components by different dosing modes. The results showed that the optimal pH for FeCl3, Alum and sequence dosing (Alum→FeCl3 and FeCl3→Alum) was at 5.0, 5.5 and 6.0-6.5, respectively. Particularly, sequence dosing (55% for both A-F and F-A) showed its advantage over single dosing (48% and 38% for FeCl3 and Alum, respectively) in DOC removal at pH 6.0-6.5 (neutral-acidic pH). The removal of EEM component and the result of MW distribution demonstrated that the removal of large MW aromatic protein-like substances was positively correlated to the DOC removal for all dosing modes. The floc diameter at different pH region also revealed a similar trend with the DOC removal for all dosing modes. In addition, the change of pH during the coagulation process proved that the dominated mechanism for single dosing is complexation and adsorption at acidic (pH 5.0-5.5) and neutral-basic pH region, respectively. However, adsorption becomes the major coagulation mechanism for sequence dosing within the whole pH range (5.0-7.5). Therefore, it is recommended to be applied and operated at neutral-acidic pH for improvement of removing IOM.

Coastal zones are complex and highly productive social-ecological systems (SES), but their resilience is increasingly threatened by a range of human activities including land use change and the expansion of port infrastructure associated with the global movement of minerals, petroleum products and other commodities. Over the last decade, the gas industry has emerged as a key driver of port development as it seeks to rapidly develop unconventional resources such as Coal Seam Gas (CSG). In many cases, unconventional gas developments are accompanied by the construction of coastal infrastructure including gas processing and liquefaction plants, pipelines and shipping facilities, used for export and import of refined gas products. This brings the gas industry into increasingly close contact with marine and coastal ecosystems. Seagrasses (marine flowering plants) are among the habitats most at risk of disturbance associated with port development. Seagrass meadows are critical to the health of marine ecosystems, playing an important role as a coastal filter for sediment and nutrients, acting as foraging and nursery habitats for wildlife, and storing carbon and other greenhouse gases (GHGs) in the oceans. The loss of seagrass meadows can therefore have secondary impacts on the broader ecosystem, including on the wildlife that depend on them for habitat, including fish, benthic invertebrates, marine turtles and sirenians (dugongs and manatees). Many of these fauna species are facing localised declines across the world as a result of multiple pressures including loss of foraging and breeding habitat, an increase in marine pollutants and fishing pressure. Adding to this complexity, infrastructure developments along the coastline are embedded within complex networks of human-environment interactions and as such, their ecological and social impacts are intimately linked. Human communities are affected by the environmental, social and economic changes that are associated with large-scale industrial developments, including a deterioration in ecosystem services, higher living costs, increased burden on healthcare and other community services and public safety concerns, in addition to economic benefits. Because coastal counities are intimately connected to the environment through the exchange of material inputs and ecosystem services, degradation of the local environment also has ramifications for local livelihoods and quality of life. Australia is currently the world’s leading exporter of coal, and is expected to become the largest global exporter of Liquefied Natural Gas (LNG) by 2018-19. Six LNG facilities are currently in operation or development around the country, three of which are located inshore of the Great Barrier Reef (GBR) on the north-eastern coast of Queensland. The GBR is perhaps best known for the natural values that make it one of the great wonders of the world, but it is also home to a number of large industrial ports and the subject of ongoing port development proposals. The proposed expansion of port development in the Great Barrier Reef World Heritage Area (GBRWHA) to support growth in the LNG and coal sectors prompted the World Heritage Council to review Australia’s management of the GBRWHA in 2012, placing the World Heritage status of the GBR in question. The review expressed strong concerns about the capacity of current governance structures to protect the ecosystems of the GBR, given the unprecedented scale and speed of industrial development along its margins, and highlighted the need to better understand the impacts of such developments on the ecology of the GBR and the local communities whose wellbeing and livelihoods depend on its resources. Although there has been much research on the social, economic and environmental impacts of inland CSG infrastructure, this has not been the case for coastal LNG plants and associated port developments. With this in mind, this thesis sought to understand how recent forms of industrial development affect complex SES in the GBRWHA through an in-depth case study of the Port of Gladstone, where recent LNG development has led to concerns over port impacts to the marine environment and social wellbeing among the local community. In so doing, I employed a trandisciplinary methodology comprising a suite of ecological and social research methods, which was subsequently developed into a broader framework for application to other contexts. The first phase of the research involved a survey of local residents in the Gladstone Region, which revealed that impacts of port development on water quality, fish health and seagrass meadows, and the socio-economic impacts associated with rapid LNG development, were of highest concern to local residents. Short-term declines in seagrass cover have been observed in a number of areas of the GBR since 2011, and these are attributed to the interaction of multiple processes including dredging, flooding and cyclones (Great Barrier Reef Marine Park Authority, 2014; McKenna et al., 2015). The research also included a component of ecological field- and laboratory-based research that examined the interactions between elevated event-based sedimentation rates and seagrasses in the Port of Gladstone. Lastly, the research drew together these two components through a critical assessement of the processes of Environmental Impact Assessment (EIA) and Social Impact Assessment (SIA) for the Gladstone LNG projects. These twin processes are designed to predict and provide a framework for managing the impacts of developments at the local scale. The findings of this research relate both to the ecology of seagrass meadows in the port of Gladstone and to the socio-economic changes that are intimately linked to environmental change. The research demonstrates that local attitudes towards LNG development in the GBR are closely linked to perceptions of environmental health before and after port development, as well as the values that local residents associate with the marine environment. The importance of coastal ecosystems to local livelihoods, lifestyles and sense of place, and their vulnerability to port-related disturbance emphasises the need to protect them into the future. Seagrasses in the Port of Gladstone demonstrate resistance to sedimentation, but growth declines significantly when these species are shaded or buried for prolonged periods, such as may occur after flood events or dredging. Additionally, the research found that the coastal setting and specific characteristics of the LNG industry – including the speed and unprecedented scale of development – have led to highly specific, and often cumulative, social and economic impacts that are difficult to predict and manage through current project-based impact assessment processes. Finally, although it is widely acknowledged that both scientific and local knowledges, including the knowledge of local indigenous peoples, play an important role in governance processes, current governance arrangements inhibit effective knowledge sharing and adaptive governance throughout the project lifecycle. This thesis provides evidence for the benefits of a more inclusive, adaptive approach to impact assessment, and also highlights the ways in which transdisciplinary research may be used to improve our understanding of complex social-ecological systems.