A field survey was undertaken in Central Kalimantan, Indonesia (Borneo) to assess the extent and practices of Artisanal and Small-scale Gold Mining (ASGM), and to measure sediment and mercury flows in the provinces’ rivers. More than forty mining operations were visited in six of the provinces largest river basins during June, July and August of 2008. Based on the survey results, this thesis estimates that 43,000 small-scale gold miners in Central Kalimantan produced 13.3 tonnes of gold in 2008 (426,000 troy ounces - ozt) worth approximately 362 million CAD (based on 2008 international gold price of 850 CAD/ozt). Mercury use was ubiquitous for leaching gold from ores in the province. Approximately 65.3 tonnes was used for this purpose in 2008, with the majority of consumption- 80% by whole-ore amalgamation operations exploiting hard-rock deposits, but producing only 13% of the gold. These estimates have been interpolated using (i) measurements and detailed observations at more than forty ASGM operations surveyed in five different regencies; (ii) numerous interviews with miners, gold shops owners and officials across these regencies; and (iii) mapping of ASGM operations using satellite imagery. Hydraulic mining methods mobilize enormous volumes of sediment and native sediment-bound mercury. Sediment and mercury fluxes associated with ASGM activities were estimated based on a river sediment sampling campaign carried out in conjunction with the ASGM survey, and on subsequent modelling of river sediment transport. On streams and tributaries, mining activities increased sediment transport by factors between 100 and 1500, resulting in a net doubling of sediment loads on large first order river channels, on which the effects of mining are diluted in space and time by channels without mining. Particulate mercury flux sampled on six of Central Kalimantan’s largest river channels averaged 60ng/L ±33%, a high figure relative to most global rivers, despite average suspended sediment concentrations of only 75mg/L ±58%. Based on a hydrological and sediment transport model, 19.4 tonnes of mercury (±30%) transits these river systems annually, dominantly transported as suspended sediment load (95%), with the remaining 5% transported as bedload. Acute mercury exposure by inhalation during the burning of mercury-gold amalgam represents an important health concern at ASGM camps and gold shops. In relation to mercury, sector improvements should focus on eradicating whole ore amalgamation, and open burning of amalgam. Eliminating whole ore amalgamation requires technological improvements at the gold liberation (crushing and milling) and concentration stages of ore processing. Elimination of open-air burning can be achieved through education, and the use of retorts, fumehoods, and mercury re-activation cells– each of these basic technologies provide mercury users with economic incentives by reducing mercury consumption. / Graduate

Shippagan Gully is a tidal inlet located near Shippagan, New Brunswick on the Gulf of Saint Lawrence. It is a particularly complex tidal inlet due to the fact that its tidal lagoon transects the Acadian peninsula and is open to the Bay des Chaleurs at its opposite end. As such, two open boundaries with phase lagged tidal cycles drive flow through the inlet, alternating direction with each tide and reaching velocities in excess of 2m/s. Hydrodynamic and morphological processes at the site are further complicated by the presence of a highly variable wave climate. Presently, shipping practices through the inlet are limited due to continual sedimentation within and immediately offshore from Shippagan Gully. As such, an extensive field study, desktop analysis and numerical and morphological modeling of Shippagan Gully have been conducted in order to provide guidance for future works. Modeling was conducted using the CMS-Wave and CMS-Flow numerical modeling system.

In this study, a numerical model is developed to determine shoreline changes due to wind wave induced longshore sediment transport, by solving sediment continuity equation and taking one line theory as a base, in existence of seawalls, groins, T-groins, offshore breakwaters and beach nourishment projects, whose dimensions and locations may be given arbitrarily. The model computes the transformation of deep water wave characteristics up to the surf zone and eventually gives the result of shoreline changes with user-friendly visual outputs. A method of representative wave input as annual average wave characteristics is presented. Compatibility of the currently developed tool is tested by a case study and it is shown that the results, obtained from the model, are in good agreement qualitatively with field measurements. In the scope of this study, input manner of long term annual wave data into model in miscellaneous ways is also discussed.

[Truncated abstract] Most of Australia, and large areas of many other continents, is drained by intermittent rivers and streams, however comparatively few biogeochemical studies have been completed for these systems. Intermittent, dryland streams are highly dynamic environments subject to unpredictable and sporadic flow. Natural disturbance from lengthy drought periods and sudden floods are typical for these systems. Without adequate baselines for natural disturbances, it is difficult to quantify other effects from anthropogenic disturbance such as dewatering, land clearing, and urbanisation, or climate change. This thesis presents work from a four-year study examining the biogeochemistry of nitrogen (N), phosphorus (P) and carbon (C) in soils and sediments of two intermittent streams (Barnett Creek and Pirraburdoo Creek) in the Pilbara region of north-west Australia. The Pilbara is an area of ancient geology and highly weathered environments that is undergoing rapid development yet is poorly understood from an ecological perspective. The principal objectives of this thesis were to determine: i) how flooding affects the spatiotemporal patterns of nutrients in intermittent stream landscapes; ii) the role of flooding in N and C mineralisation and microbial dynamics; and iii) the connections between benthic algae, microbes and nutrient availability in channel sediments. To address these objectives, three field studies and two incubation experiments were conducted. Field studies at Barnett Creek indicated that flooding reduced the spatial heterogeneity of available soil nutrients and microbes in the stream landscape, and that topography (relative elevation) in the stream landscape was of less importance in influencing nutrient and microbial patterns than flooding or landscape position. ... Field studies at Pirraburdoo Creek indicated that microbial biomass and activity increased in benthic algal mats during mat senescent stages, and decreased after flooding when mat biomass peaked. Benthic algae grew rapidly in gravel run environments after flooding, while declining in pools, and demonstrated moderate N limitation and strong P limitation. Pools had two to eight times greater NO3-N, three to five times more total N, and two to three times more labile P, OC and total C than either pools after flooding, or runs before or after flooding. Hence, the pools at Pirraburdoo Creek represented a local, interflood store of nutrients in otherwise nutrient-poor landscape, when connectivity to upstream reaches or upland environments was weak or non-existent. This thesis provides the first detailed analysis of soil and sediment biogeochemical responses to flooding for intermittent streams in the Pilbara region and for semi-arid Australia. Further pressing questions raised by this work include: What is the key pulse size and frequency for maintaining Pilbara riparian communities as well as soil microbial function? How do the spatio-temporal nutrient and microbial patterns observed persist over (i) multi-decadal scales, (ii) mega-spatial (larger landscape to regional) scales, (iii) different flood frequency-magnitude regimes, and (iv) different stream sizes? Stream biogeochemistry is a burgeoning field, and it is therefore reasonable to expect such existing gaps in knowledge may be addressed in the near future.

Sediment diagenesis in aquatic systems is usually understood to be controlled by the concentrations of both organic carbon and the oxidant. However, the concept that sediment respiration may be limited by the supply of organic carbon, even in systems with moderate concentrations of organic carbon in the water column, has yet to be fully explored. Typically we assume that a direct coupling between water column and sediment diagenesis processes occurs and the chemical evolution of porewater and surface water are linked through fluxes of chemical species across the sediment-water interface. While the dynamics of supply of particulate organic carbon (POC) to the sediments via plankton deposition and resuspension, has previously been examined, the fate of dissolved organic carbon (DOC) once in the sediments, has rarely been investigated. A series of experiments comprising batch tests, microcosms and sediment cores were conducted on sediment and water from four diverse field sites in which sediment respiration was considered to be carbon limited. Three sites were oligotrophic, acidic lakes and the fourth an oligotrophic coastal embayment. During each experiment dissolved organic carbon was added and measurements were undertaken of solutes that were considered participants in diagenetic processes. While each system differed in its chemical, biological and geological makeup, a key commonality was the rapid onset of anoxic conditions in the sediments irrespective of the overlying water oxygen concentrations, indicating lack of direct coupling between biogeochemical processes in the water column and sediments. Also, similar apparent DOC remineralisation rates were observed, measured solute fluxes after the addition of DOC indicated adherence to the ecological redox sequence, and increased ammonium concentrations were measured in the overlying waters of the acidic microcosms. In marine system experiments it was noted that diagenetic respiration, as indicated by decreasing concentrations of oxygen in the overlying water, increased rapidly after labile DOC was added. To explore the influence of geochemical processes on sediment respiration, a diagenetic model was tested against the laboratory data. The model was able to capture the rapid changes observed in the microcosms after addition of DOC in both the marine and acidic systems experiments. The model has the potential to serve as an essential tool for quantifying sediment organic matter decomposition and dissolved chemical fluxes. This work has focussed our attention on the control of DOC availability on sediment respiration and thus its ultimate control on solute fluxes across the sediment water interface. The results highlight the need to understand and quantify the supply of DOC to the sediment (as POC or already as the dissolved form), its transport through the sediment and its eventual remineralisation. This understanding is critical for improved management of aquatic systems, possibly even in systems where water column organic carbon is plentiful but sediment respiration is constrained by high organic carbon turnover rates in the water column and a resulting low flux of organic carbon to the sediment.

Thesis (doctoral)--Universität Bremen, 2003. / Includes bibliographical references.

A program for selecting the optimal wave conditions for morphodynamically accelerated simulations of coastal evolution (‘OPTIWAVE’) has been constructed using a novel Genetic Algorithm approach. The optimization routine iteratively reduces the complexity of an incident wave climate by removing the events that contribute least to a target sediment transport pattern, and then ‘evolving’ a new set of weights for the remaining wave conditions such that the target sediment transport pattern (and magnitude) is optimally maintained. The efficacy of OPTIWAVE to satisfactorily reduce the incident wave climate is tested against three coastal modeling paradigms of increasing complexity: (a) A simple 1-D beach profile model (no tides); (b) A 2-D micro-tidal beach; (c) A tidal inlet, where the interaction between waves, tides, and wave-current interaction, adds significant complexity. The simple test case for a beach profile shows that OPTIWAVE is successfully capable of maintaining a target profile-integrated long-shore sediment transport rate. The calculated skill and RMSE of the reduced wave climate is a good indicator of its ability to reproduce the target sediment transport pattern. The optimal number of wave conditions is identified by an ‘inflection point’ at a critical number of wave conditions, where less complex a wave climate results in substantially reduced skill (increased error). The assumption that the ability of OPTIWAVE to reproduce a target sediment transport field is a valid proxy for the potential skill of a morphologically accelerated simulation is assessed for the case of a 2D micro-tidal beach. The skill of the accelerated models, which use a state-of-the-art ‘event-parallel’ method of simulating bed evolution from multiple wave conditions in parallel, is tested against a ‘brute force’ reference simulation that considers the full wave forcing. A strong positive correlation is found between the skill of the reduced wave climate to reproduce a target sediment transport pattern, and the resultant skill of the accelerated morphodynamic model against the ‘brute force’ reference simulation. Finally, the ability to combine reduced wave and tide climates for simulations that must consider both wave and tidal forcing, is assessed against a ‘brute force’ reference simulation of the seasonal evolution Ancao inlet, Algarve, Portugal. The reference simulation is validated against a comprehensive field dataset collected in 1999, and is shown to qualitatively reproduce key features of inlet behavior over a seasonal period. The combination of reduced wave and tidal climates in accelerated ‘event-parallel’ models did not successfully reproduce the reference seasonal morphological evolution of Ancao inlet. Assessing the model Brier Skill Score showed that the model was more successful in reproducing the reference morphology in areas dominated by tidal forcing, but did not have any predictive power in regions where morphological evolution is due to some combination of both wave and tidal processes.

Les particules en suspension transportées dans les réseaux hydrographiques résultent des processus de rivière et des apports depuis les versants. Nous avons étudié dans cette thèse la dynamique des tailles de particules le long du continuum versant-rivière afin d'apporter des éléments de réponse à la réflexion aujourd'hui menée sur les distances de transport et sur le concept de connectivité sédimentaire. Des observations de terrain sont menées à l'exutoire d'un bassin versant de tête (~20 km²). Elles mettent en évidence une corrélation positive entre débit liquide et taille des particules. L'établissement et la mise en oeuvre d'un protocole de mesure original montre que les particules sont agrégées. A cette échelle, les apports des versants semblent importants pour expliquer les variations de taille des particules. Des expériences de laboratoire utilisant un canal annulaire sont menées et indiquent qu'une partie de ces variations peut être attribuée à la désagrégation ou à la floculation des particules dans l'écoulement. Des variations de taille notables sont dues au type de sol. Elles sont moindres à la fin des évènements schématiques simulés en canal, suggérant que l'écoulement prend une part prépondérante pour expliquer les variations de taille des particules. Cet effet du type de sol a motivé l'étude des processus de versant, et en particulier ceux de la pluie. Des expériences de simulations de pluie menées en laboratoire (~1 m²) sur deux sols révèlent que l'augmentation de l'énergie cinétique de la pluie a tendance à générer des agrégats plus fins. Une paramétrisation du détachement par la pluie par fraction granulométrique est développée sur la base de ces expériences et implémentée au sein de deux modèles numériques d'érosion hydrique à base physique. Les simulations numériques confirment que cette tendance a des impacts sur les exports à l'échelle du versant. Enfin, des variations de granulométrie en lien avec l'énergie cinétique de la pluie sont perceptibles lors d'observations de terrain à l'échelle du versant (~ 100 m²), confirmant l'importance d'une description correcte du forçage pluviométrique. / The suspended particles of catchment networks are dependent on both river and hillslope erosion processes. During this thesis, the particle size dynamics was studied along this continuum in order to improve the understanding of particle delivery from hillslopes to the outlets of headwater catchments. Field measurements were conducted at the headwater catchment scale (~20 km²). The discharge displayed a positive correlation with the particle size. An original measurement protocol has been set up and it demonstrated that particles were mostly aggregated. The inputs from hillslopes were possibly involved in some of the variations of the measured particle size. Laboratory experiments carried out using an annular flume demonstrated that a part of these variations could be explained by disaggregation or flocculation within the flow. Important variations due to the soil type were observed. However, they were less pronounced in the falling limbs of the schematic flood events, suggesting that flow conditions progressively became more important than the soil signature. The latter encouraged the analysis of hillslope processes, among which a special attention was given to the rainfall effects. Rainfall simulation experiments (~1 m²) demonstrated for two soils that an increase in the rainfall kinetic energy resulted in smallest aggregates detached from the soil matrix. The importance of this mecanism at the hillslope scale (~ 100 m²) with regard to runoff selectivity was demonstrated developing a size-dependent detachment parametrisation included in two physically based numerical models. Finally, the effects of the rainfall kinetic energy on the particle size were observed during field measurements made at the plot scale as well, underlining the need to adequatly describe the rainfall forcing field at this scale.

O presente trabalho visa caracterizar, através de experimentos numéricos, a hidrodinâmica e o transporte de sedimentos em suspensão no sistema estuarino de Caravelas e Peruípe sob diferentes condições forçantes. O sistema é formado por canais que estabelecem a conexão entre os rios Caravelas e Peruípe. Dados de nível de água e velocidade de correntes, obtidos em coletas de campo foram utilizados para aplicar e calibrar o modelo numérico MOHID. Diferentes experimentos numéricos, simulando condições de maré de sizígia e de quadratura com diferentes condições de descarga fluvial, foram realizados. A partir destas simulações foram obtidas distribuições espaciais e pontuais da concentração de sedimentos em suspensão e das correntes forçadas pela maré integradas verticalmente. Em condições de sizígia o estuário é caracterizado por correntes mais intensas e assimétricas, com dominância de vazante. As maiores concentrações médias de sedimento em suspensão ocorreram em condições de sizígia e o transporte de sedimentos resultante foi em direção ao oceano, em função do domínio das correntes de maré vazante. Os experimentos numéricos mostram que os canais que conectam os dois estuários têm papel relevante na dinâmica local. Eles possuem influência na dinâmica sedimentar do sistema estuarino. A hidrodinâmica e o balanço sedimentar do sistema são principalmente modulados pela altura da maré, com pouca contribuição do aporte de água doce. / The aim of this work is to characterize, through numerical modeling experiments, the hydrodynamics and suspended sediment transport dynamics in the Caravelas ? Peruípe estuarine system under different forcing conditions. The system comprises channels that connect the Caravelas and Peruípe rivers. Water level and current velocity data obtained through field campaigns were used to apply and calibrate the MOHID numerical model. Different numerical experiments simulating spring and neap tides with different river discharge conditions have been conducted. Based on these simulations, the hydrodynamics and spatial and temporal distributions of suspended sediment concentrations have been analyzed. During spring tide the estuary is characterized by intense and asymmetric currents (ebb dominated). The highest average suspended sediment concentration occurred during spring tide conditions, with net sediment transport being seaward. The numerical experiments show that the connecting channels play a relevant role in the local suspended sediment dynamics. The hydrodynamic and sediment balance in the system are modulated mainly by the tidal range, with little influence from the freshwater supply.

Submitted by GUILHERME HENRIQUE FIOROT null (ghfiorot@aluno.feis.unesp.br) on 2016-08-31T16:48:18Z No. of bitstreams: 1 GHFiorot-tese-unesp.pdf: 21279930 bytes, checksum: f08d052fded3d144bcad4b9a9f1c007f (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-01T17:08:21Z (GMT) No. of bitstreams: 1 fiorot_gh_dr_ilha.pdf: 21279930 bytes, checksum: f08d052fded3d144bcad4b9a9f1c007f (MD5) / Made available in DSpace on 2016-09-01T17:08:21Z (GMT). No. of bitstreams: 1 fiorot_gh_dr_ilha.pdf: 21279930 bytes, checksum: f08d052fded3d144bcad4b9a9f1c007f (MD5) Previous issue date: 2016-07-01 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Dentro da temática de riscos naturais, mais precisamente no contexto das corridas de lama, esta tese surge da necessidade que existe na literatura em melhor se conhecer as características temporais destes eventos. A chuva, fonte da vazão liquida, conduz aos escoamentos superficiais, responsáveis pela redução da coesão do material sedimentar do solo (areia e argila) e seu consequente transporte. Em locais de topografia íngreme, de montante a jusante, a vazão sólida do escoamento principal pode, eventualmente, evoluir devido às contribuições laterais de pequenos escoamentos, alterando não só as propriedades reológicas do fluido e dinâmicas do escoamento, como se manter até que o transporte sólido atinja elevada concentração na composição do fluido. Na primeira parte desta tese, um experimento de superfície livre foi projetado para reproduzir escoamentos superficiais sobre um fundo móvel, com o objetivo de estudar propriedades não-permanentes do transporte de sedimentos. Um sistema de medição foi projetado e construído com o intuito de medir quase instantaneamente a vazão sólida e suas correlações com as propriedades hidráulicas do escoamento. Este aparato é também utilizado para observar a influência de instabilidades de superfície livre sobre o transporte. Um conjunto de resultados é apresentado e analisado e mostra que a presença de ondas pode, em média, reduzir a quantidade total de sedimentos transportada. Na segunda parte desta tese, a dinâmica de escoamentos com elevada concentração de sedimentos é estudada. Neste trabalho, executa-se a aplicação de um modelo de primeira ordem de roll waves para fluidos de reologia Herschel-Bulkley para simular um evento natural registrado na literatura. Os resultados apresentados mostram que roll waves poderiam, de fato, ser identificadas no evento e que a amplitude média observada poderia ter sido estimada com 8% de incerteza. Assim, um modelo mais complexo para a solução do perfil de velocidade é proposto, adicionando a porosidade do solo ao problema. Resultados do modelo são comparados com simulações numéricas. Uma análise paramétrica é efetuada e o caso de estudo é novamente avaliado. Como conclusão geral do trabalho, a presença de fenômenos não-estacionários durante a evolução escoamento superficial - corrida de lama afeta a dinâmica global do sistema acoplado hidráulica-transporte de sedimentos, quando comparado ao caso permanente e uniforme. Assim, a verificação de que tais fenômenos podem aparecer deve constituir parte de projetos engenharia, especialmente quando estes, em situações de catástrofes, envolvem danos a infraestruturas civis e quase sempre perdas de vidas, como é o caso das corridas de lama. / This thesis was motivated by the need to better understand time-dependent features related to mudflow evolution on natural sloped channels. Basically, the research is focused on events that are confined in channels formed due to the topography. The rain, source of the liquid discharge, generates the runoff flow which is responsible for wetting the soil surface, promoting reduction of soil cohesiveness and erosion of small particles such as clay and sand. From this point, the sediment transport can increase as small water flows merge and form greater streams. The scenario keeps its evolution until it reaches high concentration of particles in the fluid mixture. In the first part, to study the non-permanent feature of sediment transport, an open-channel experiment was designed for simulating runoff flow over a mobile bed. A measurement system was designed and constructed to instantaneously inspect the solid discharge of particles and the flow friction at the bed. This apparatus is further used to explore the influence of free-surface waves on the sediment transport. Hydraulic properties of flows are qualitatively and quantitatively studied and data are used to correlate characteristics of flow and sediment transport. A set of experimental runs is presented and explored. Analysis of results shows that for fixed flow conditions, waves induce an overall smaller quantity of transported sediment. In a second part, the dynamics of high concentrated flows is addressed and this thesis attempts to apply a first-order roll-wave model for Herschel-Bulkley laminar fluid flow to a registered natural event. Results presented point out that roll waves could have occurred during this already published case-study event. Simulations could predict wave heights within 8% on uncertainty with respect to the mean amplitude of measured waves. Finally a new theoretical solution for the velocity profile is proposed taking into account the porosity of the bed. Results are then compared with numerical simulation performed in FLUENT. A parametric analysis is employed and the case-study is once again evaluated. As general conclusion, the non-permanent phenomena that can appear during the evolution of a mudflow event affect the overall dynamics of the coupled system (hydraulic-sediment transport) in comparison to the steady and uniform case. Verifying that such phenomena could appear should indeed be an important part in hydraulic engineering projects, especially when dealing with lives, which is the case of mudflows. / CNPq: 201557/2012-6