Anlagda våtmarker i avrinningsområden från jordbruksmarker mottar ofta vatten med höga halter av partikelbunden fosfor. Den viktigaste processen för avskiljning av inkommande partikelbunden fosfor är sedimentation. Resuspension är en process som motverkar netto-sedimentationen av partiklar och kan således minska våtmarkers förmåga att hålla kvar fosfor. Syftet med den här studien var att undersöka om A. aquaticus påverkar resuspensionen av partiklar, och om större tätheter av A. aquaticus orsakar större turbiditet i vattenmassan. Två försök genomfördes i plastakvarier med sediment insamlat från våtmarker anlagda på lerjord. Varje försöksuppställning bestod av en behandling och en kontroll utan några djur. I det första försöket innehöll behandlingen A. aquaticus motsvarande en täthet på 2083 individer m-2 och i det andra försöket en täthet på 500 individer m-2. Turbiditeten mättes med en turbidimeter en gång per dag under sju dygn. Aktiviteten hos A. aquaticus orsakade en signifikant högre turbiditet i vattenmassan i behandlingen än i kontrollen. Turbiditeten var i genomsnitt 161 NTU i akvarier med 2083 individer m-2 och 37 NTU i akvarier med 500 individer m-2. Slutsatsen som drogs är att förekomst av A. aquaticus skulle kunna öka resuspensionen av partiklar i våtmarker. Detta kan i sin tur ha en påverkan på våtmarkers förmåga att hålla kvar fosfor som är bundet till lerpartiklar. / Constructed wetlands in agricultural catchments with clay soils often receive water with high concentrations of particle-bound phosphorus. Sedimentation of particle-bound phosphorus is the main retention process. Resuspension is a process that counteracts net sedimentation of the particles and can therefore reduce phosphorus retention in wetlands. The aim of this study was to investigate if A. aquaticus through bioturbation affects the resuspension of particles, and if a larger density of A. aquaticus causes a larger turbidity in the water column. The experimental design included plastic aquariums with sediment collected from wetlands constructed on clay soils. There were two experiments, each with a treatment and a control with no animals. In the first experiment, the treatment contained A. aquaticus at a density of 2083 individuals m-2. In the second experiment the treatment contained A. aquaticus at a density of 500 individuals m-2. Turbidity was measured with a turbidimeter once a day over the course of seven days. The bioturbation activity of the A. aquaticus caused a significantly larger turbidity in the water column in the treatment than in the control. The turbidity was on average 161 NTU in the presence of 2083 individuals m-2 and 37 NTU in the presence of 500 individuals m-2. The conclusion was that the presence of A. aquaticus can increase resuspension of particles in wetlands. This could have a negative impact on the ability of wetlands to retain phosphorus that is bound to particles.

Fosfor (P) är ofta det begränsande ämnet i akvatiska system och kan i höga mängder bidra till övergödning i sjöar och hav. För att minska tillförseln av partikelbunden fosfor som läcker från jordbruksmark kan våtmarker anläggas i avrinningsområdet. För en effektiv avskiljning är det viktigt att partiklar sedimenterar i våtmarken och stannar i sedimentet. Studier har visat att vissa karpfiskar och märlkräftor genom bioturbation kan orsaka resuspension av partiklar, samt att effekten ökar med ökad täthet. Syftet med denna studie var att undersöka om även makroevertebraten Asellus aquaticus (sötvattensgråsugga) kan orsaka resuspension av partiklar. Två hypoteser undersöktes: (i) A. aquaticus orsakar resuspension av sedimenterade partiklar; (ii) ökad täthet av A. aquaticus ger ökad resuspension. Två försök genomfördes och varje försöksuppställning bestod av 15 akvarier, varav finpartikulärt sediment och bäckvatten tillsattes till tio stycken medan fem innehöll endast bäckvatten. I hälften av akvarierna med sediment tillsattes A. aquaticus i olika täthet för försöken. Försöken pågick i sju dygn med dagliga mätningar av vattnets grumlighet. Resultat från försöken bekräftade båda hypoteserna. Genomsnittlig grumlighet efter sju dygn var 161 NTU (143 mg L-1 TSS) vid en täthet på 2083 A. aquaticus m-2 och 37 NTU (26 mg L-1 TSS) vid 500 A. aquaticus m-2. Studiens resultat indikerar att A. aquaticus kan ha en negativ påverkan på retentionen av partikelbunden fosfor i våtmarker. / Phosphorus (P) is often the limiting nutrient in aquatic systems and can in excessive quantities cause eutrophication in lakes and seas. To reduce the input of particle-bound phosphorus leaking from agricultural land, wetlands can be constructed as traps for particles. It is important that particles settle in the wetland and remain in the sediment. Studies have shown that bioturbation by e.g. common carp and amphipods can cause resuspension of settled particles, and that the effect increases with an increasing density of organisms. The purpose of this study was to examine if the macroinvertebrate Asellus aquaticus can also cause resuspension of particles. Two hypotheses were tested: (i) bioturbation by A. aquaticus will cause resuspension of particles; (ii) an increased density of A. aquaticus increases the resuspension of particles. This was tested in two experiments, each of which included 15 aquaria. In ten of these, sediment and stream water were added. To five of the aquaria with sediment, A. aquaticus were added in different densities for the two experiments. Water turbidity was measured daily for seven days. The results confirmed both hypotheses. Average turbidity after seven days was 161 NTU (143 mg L-1 TSS) at a density of 2083 m-2 and 37 NTU (26 mg L-1 TSS) at 500 m-2. The results indicate that the presence of A. aquaticus may have a negative impact on the retention of particle-bound phosphorus in wetlands.

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

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 (Ph.D.)--Mississippi State University. Department of Civil and Environmental Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Sept. 23, 2009). Thesis advisor: John S. Schwartz. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Depuis la fin du Petit Age Glaciaire, les glaciers du massif du Mont-Blanc se retirent et libèrent ainsi d’importants volumes de sédiments. La fourniture sédimentaire grossière, qui est l’un des éléments de contrôle principaux de l’activité géomorphologique des torrents proglaciaires, peut être profondément modifiée. Dans le contexte de la vallée de Chamonix, où la pression urbaine est très forte, l’accélération du retrait glaciaire soulève des questionnements de la part à la fois des gestionnaires et des scientifiques sur l’évolution des risques et de la gestion des flux solides.L’objectif de ce travail de thèse est d’étudier le couplage sédimentaire entre les espaces libérés des glaces et les torrents jusqu’en fond de vallée, avec un double niveau de réponse. Le premier niveau permet de comprendre les trajectoires géomorphologiques des systèmes glacio-torrentiels depuis la fin du Petit Age Glaciaire et à l’échelle de la vallée. Il est étayé par une analyse géomorphologique et par l’étude de l’évolution du réseau hydrographique, qui s’appuie sur une modélisation et sur de nombreux documents d’archive. Cette étape souligne la diminution du potentiel du système torrentiel à remobiliser des sources sédimentaires. En conséquence, l’activité des torrents a fortement baissée depuis 150 ans. La seconde approche concerne l’étude des dynamiques récentes basée sur la comparaison diachronique de MNT LiDAR à haute résolution. Elle se focalise sur les trois systèmes glacio-torrentiels les plus grands de la vallée (Argentière, Mer de Glace et Bossons) dont les activités morphogènes ont pu être interprétées sous le prisme de crues d’occurrence décennale survenues en août 2014. Cette partie montre l’efficacité des processus de stockage sédimentaire au sein même des espaces désenglacés, ainsi que l’importance du forçage humain sur la morphogénèse torrentielle qui prime désormais sur l’influence du retrait glaciaire. L’état de la fourniture sédimentaire résulte actuellement de l’impact des différentes infrastructures, telles que les captages sous-glaciaires ou l’autoroute d’accès au Tunnel du Mont Blanc.Nos résultats montrent donc une première phase de diminution de l’activité torrentielle, principalement causée par le retrait des glaciers de 1850 à 1950, puis les conséquences pression des activités humaines sur les évolutions hydromorphologiques. La baisse de la torrentialité est toutefois ponctuée de quelques évènements, comme la crue du septembre 1920 sur l’Arveyron de la Mer de Glace, dont nous avons reconstitué les conséquences géomorphologiques. Malgré leur intensité, les effets de ces crues restent néanmoins relativement limités à l’aval immédiat des glaciers.Contrairement donc aux hypothèses initialement soulevées, le retrait glaciaire n’implique pas une augmentation de la fourniture sédimentaire, mais au contraire une diminution des apports du fait de la déconnexion entre les espaces désenglacés et les systèmes torrentiels. / Since the end of Little Ice Age, glaciers of the Mont blanc massif are retreating and large sediment volume are releasing from the ice. Thus, sediment supply, which is a main control factor of the proglacial stream geomorphic activity, could be deeply modified. Therefore, the consequences on the sediment fluxes and the risk management need to be understanding because of the present acceleration of glacier retreat and urban sprawl in the Chamonix valley. The goal of this thesis is to study the sediment coupling between stream systems and areas released by glaciers. A first approach allows understanding the geomorphic trajectory of proglacial system at the Chamonix scale since the end of the Little Ice Age. Our results supported by modelling and archives analyses, show the decreasing capacity of the hydrographic pattern to be connected with sediment sources. The second approach is lead on the LiDAR DEM multi-temporal comparison. It focuses on the three main proglacial systems: Argentière, Mer de Glace and Bossons, whom occurred a decennal flood during the 2014 summer. This part of our study underlines the storage efficiency into deglaciated areas and the increasing role of anthropic forcing. Present sediment yield to proglacial stream is leaded by facilities such as the Mont Blanc Tunnel substructure or the subglacial harnessing. Our results show that the decreasing geomorphic activity of proglacial stream in the Chamonix valley is mainly caused by glacier retreat from the early 18th Century to the middle 20th century, then it is leaded by the increasing human pressure. Nevertheless, the fall of stream activity is punctuated by extreme events, such as the 1920 flood in the Arveyron of the Mer de Glace that we reconstructed the geomorphic consequences. Despite their intensity, effects of that king of events are limited close to the glacier downstream. Contrary to our initial hypotheses, glacier retreat in the Chamonix Valley, is not follow by a geomorphic crisis of proglacial streams because of the disconnectivity between sediment released from the ice and stream systems.

L’érosion et la redistribution des particules détachées représentent un enjeu environnemental, sociétal et économique majeur. Afin de mettre en place des mesures de protection, il est nécessaire d’identifier et quantifier les sources et puits de sédiments ainsi que leur dynamique spatiale et temporelle. L’objectif de cette thèse est donc de dresser le bilan sédimentaire d’un large bassin versant (Loire Bretagne, 155 000 km2) aux paysages contrastés. Sur les versants, les particules détachées issues des différentes sources (érosion diffuse, concentrée, mouvements de masse) représentent un apport de 1.5 * 107 t.an−1 (contribution respective au stock : 82.4%, 12.9%, 4.7%). La prise en compte de la distribution spatiale des processus mis en jeu dans le transfert particulaire et des caractéristiques du site d’étude (ruissellement par saturation en zone de plaine et présence de haies) dans un indice qualitatif permet d’évaluer la connectivité des versants. L’érosion de berge contribue également au stock sédimentaire à hauteur de 6.9 * 105 t.an−1. Au final, seuls 5% des particules détachées, toutes sources confondues, sont transportées jusqu’à l’exutoire du bassin versant et témoignent du fort taux de dépôt au sein du bassin. En parallèle, une valorisation de la base de données des éléments dissous permet de montrer l’importance des flux sédimentaires exportés sous forme dissoute (~ 90% des exports totaux). La représentation de l’ensemble de ces résultats à différentes résolutions spatiales permet de développer une approche qualitative du transfert particulaire et d'identifier les zones à risque. / Erosion and particles redistribution represent major environmental, societal and economic issues. To adopt protection measures, it is essential to identify and quantify sources and sinks of sediment and their spatial and temporal dynamic. The aim of this work is thus to establish a sediment budget for a large river basin (Loire and Brittany river basin 155,000 km2) with contrasted landscapes. On hillslopes, detached particles from the miscellaneous form of erosion (sheet and rill erosion, gullies and mass movements) represent a supply of 1.5 * 107 t.yr−1 (contribution to the stock of 82.4%, 12.9%, and 4.7% respectively). The consideration of the spatial distribution of processes involved in sediment transport and the characteristics of the study site (soil saturation and presence of hedgerows) in a qualitative landscape-based index allows us to assess the hillslope connectivity. Bank erosion also participates in the sediment budget with 6.9 * 105 t.yr−1 of material provided to the river network. In the end, only 5% of detached particles, from all sources of sediment, reach the basin outlet indicating a substantial deposition on the way from source to outlet. In parallel, the use of the database of dissolved elements allows us to highlight the importance of the dissolved sediment fluxes ( 90% of the total exports of the Loire river). The presentation of all results at different spatial scales permits to provide a qualitative approach of sediment source-to-sink transfers and to identify hotspots of erosion and transfers.

Rapporten ämnar undersöka bottensediment bärgade från ett område i västraGotlandsbassängen i Östersjön. Östersjön är ett ansträngt bräckvattenhav medutbredda övergödningsproblem, döda bottnar och hotad biologisk fauna. Söktaresultat berör fosforhalt, förekommande metaller, mineralsammansättning,kornstorleksfraktioner samt organisk halt för ett projekt där målet ärsedimentbärgning för betongindustrin och brytning av fosfor som arbetar motövergödning med kretslopp och cirkulär ekonomi. Detta uppnås med följandeanalysmetoder: ICP-MS, XRD, TGA och laserdiffraktometer tillsammans med RISE CBI. Analyserna visade att sedimentet är ett finsediment med en hög organisk halt ochkan klassificeras som postglacial siltgyttja och innehåller 1,63 mg/kg TS fosfor.Förekommande mineral är albit, kvarts och glimmer. Metaller som påträffades var,men inte uteslutande kisel, 214000 mg/kg TS, aluminium 80600 mg/kg torrt sediment(TS) och järn 49900 mg/kg TS. Under diskussionen hanteras renings-ochseparationsprocesser för fosfor och metaller, av vilka Bio-P metoden ochhyperackumulerande växter tas upp. / This project aimed to investigate sediment salvaged from an area in the westernGotland basin of the Baltic Sea. The Baltic Sea is a stressed brackish water sea withextensive eutrophication problems, so-called dead zones and threatened fauna. Theresults relate to phosphorus content, prevalent metals, mineral composition, grainsize distribution, and organic content. This work is part of a project where the goal isphosphorous recovery for concrete and phosphorus mining with circulation andcircular economics to better the current situation in the Baltic sea. The physical andchemical properties of the sediments were investigated using the following analyticalmethods: ICP-MS, XRD, TGA and laser diffractometer together with RISE CBI.The results show that the sediment is a postglacial silt gyttja, with a phosphorouscontent of 1.63 mg / kg of dry sediment (DS). Existing minerals are albite, quartz andmica. Elements found were, but not exclusively silica, 214000 mg/kg DS, aluminium80600 mg/kg DS and iron 49900 mg/kg DS. Relevant purification and separation processes for phosphorus and metals, of which the Bio-P method and hyper-accumulating plants are two, are discussed.