有机质对细颗粒泥沙静水絮凝沉降特性的影响

在CaCl2 和MgCl2 浓度为 0～ 1.0mmol L ,泥沙浓度为 10g L时 ,本文用吸管法研究了有机质对细颗粒泥沙絮凝沉降的影响 ,结果表明 :在液面下同一深度 ,有机质并不影响泥沙浓度随时间呈指数衰减的变化规律。但去除有机质后 ,细颗粒泥沙絮凝的最佳电解质浓度降低 ;对于相同的电解质浓度 ,其絮凝沉降加快 ,泥沙平均沉速明显增大

东海悬沙浓度垂向分布规律研究

细颗粒泥沙运动及冲淤变化在深水航道整治工程中至关重要，研究细颗粒悬沙运动，悬沙浓度是一个关键。研究悬沙浓度，首先要研究悬沙浓度的水平和垂向分布，其中，垂向浓度又是海水中悬沙三维分布研究的核心。 本文以2006年8月的长江口外海域的悬沙数据资料为基础，把经典的泥沙扩散理论模型和两相流颗粒浓度分布的运动理论模型的关于垂向含沙分布的理论，作为本研究的回归模型的理论依据，通过观测获得的悬沙浊度资料对应求出观测垂向剖面浓度，采用相关分析和多元线性回归的方法，分析了长江口外海域的悬沙浓度垂向分布特点，回归出悬沙垂向浓度分布模型，为了更好的揭示水动力条件对浅海陆架区悬浮物的影响，本文还用短期资料的潮流准调和分析方法，对东海三定点分表中底三层的25小时连续海流资料进行分析，计算了三测站六个主要分潮的北、东分量潮流调和常数，由于原始记录带有扰动信息，经过预处理计算出来常规每小时一次的海流观测结果，把海流加入了悬沙垂向分布模型。并在整个研究区域验证了悬沙垂向浓度分布模型。结果表明：垂向浓度的大小与相对水深相关性良好，而水深对其的影响则表现在梯度变化方面。通过悬沙垂向浓度模型，由海水底层浓度和海流可以计算得到不同水层的悬沙浓度；有效性检验和拟合结果检验表明，该模型置信度较高，且能够较为有效的预测海水中、上层水体的悬沙浓度值。

Understanding and modelling hydrological and soil erosion processes in burnt forest catchments

Forest fires implications in overland flow and soil erosion have been researched for several years. Therefore, is widely known that fires enhance hydrological and geomorphological activity worldwide as also in Mediterranean areas. Soil burn severity has been widely used to describe the impacts of fire on soils, and has being recognized as a decisive factor controlling post-fire erosion rates. However, there is no unique definition of the term and the relationship between soil burn severity and post-fire hydrological and erosion response has not yet been fully established. Few studies have assessed post-fire erosion over multiple years, and the authors are aware of none which assess runoff. Small amount of studies concerning pre-fire management practices were also found. In the case of soil erosion models, the Revised Universal Soil Loss Equation (RUSLE) and the revised Morgan–Morgan–Finney (MMF) are well-known models, but not much information is available as regards their suitability in predicting post-fire soil erosion in forest soils. The lack of information is even more pronounced as regards post-fire rehabilitation treatments. The aim of the thesis was to perform an extensive research under the post fire hydrologic and erosive response subject. By understanding the effect of burn severity in ecosystems and its implications regarding post fire hydrological and erosive responses worldwide. Test the effect of different pre-fire land management practices (unplowed, downslope plowed and contour plowed) and time-since-fire, in the post fire hydrological and erosive response, between the two most common land uses in Portugal (pine and eucalypt). Assess the performance of two widely-known erosion models (RUSLE and Revised MMF), to predict soil erosion rates during first year following two wildfires of distinctive burn severity. Furthermore, to apply these two models considering different post-fire rehabilitation treatments in an area severely affected by fire. Improve model estimations of post-fire runoff and erosion rates in two different land uses (pine and eucalypt) using the revised MMF. To assess these improvements by comparing estimations and measurements of runoff and erosion, in two recently burned sites, as also with their post fire rehabilitation treatments. Model modifications involved: (1) focusing on intra-annual changes in parameters to incorporate seasonal differences in runoff and erosion; and (2) inclusion of soil water repellency in runoff predictions. Additionally, validate these improvements with the application of the model to other pine and eucalypt sites in Central Portugal. The review and meta-analysis showed that fire occurrence had a significant effect on the hydrological and erosive response. However, this effect was only significantly higher with increasing soil burn severity for inter-rill erosion, and not for runoff. This study furthermore highlighted the incoherencies between existing burn severity classifications, and proposed an unambiguous classification. In the case of the erosion plots with natural rainfall, land use factor affected annual runoff while land management affected both annual runoff and erosion amounts significantly. Time-since-fire had an important effect in erosion amounts among unplowed sites, while for eucalypt sites time affected both annual runoff and erosion amounts. At all studied sites runoff coefficients increase over the four years of monitoring. In the other hand, sediment concentration in the runoff, recorded a decrease during the same period. Reasons for divergence from the classic post-fire recovery model were also explored. Short fire recurrence intervals and forest management practices are viewed as the main reasons for the observed severe and continuing soil degradation. The revised MMF model presented reasonable accuracy in the predictions while the RUSLE clearly overestimated the observed erosion rates. After improvements: the revised model was able to predict first-year post-fire plot-scale runoff and erosion rates for both forest types, these predictions were improved both by the seasonal changes in the model parameters; and by considering the effect of soil water repellency on the runoff, individual seasonal predictions were considered accurate, and the inclusion of the soil water repellency in the model also improved the model at this base. The revised MMF model proved capable of providing a simple set of criteria for management decisions about runoff and erosion mitigation measures in burned areas. The erosion predictions at the validation sites attested both to the robustness of the model and of the calibration parameters, suggesting a potential wider application.

Variação espacial e sazonal de elementos maiores e traços no estuários do Rio Curimataú (RN), através de dados geoquímicos e de sensoriamento remoto

The Curimataú estuary is located in the oriental coast of Rio Grande do Norte State in Brazil. Its importance resides in the fact that this region possesses one of the last portions of preserved mangrove in the Rio Grande do Norte State. Nevertheless, it has been severely affected by many anthropogenic activities, as sugarcane monoculture and shrimp farming. Former works demonstrated that an accumulation of heavy metals is occurring in oysters in this estuary, and perhaps it could be explained by the input of metals in this ecosystem deriving from the shrimp farming. To better understanding the origin of these metals, bottom sediment samples, cores and suspended particulate matter were collected for a characterization of metal concentrations (Al, Ba, Cd, Cu, Cr, Fe, Mn, Ni, Pb, Zn) and to determine the potentially bioavailable metals. Additionally, the enrichment ratio for each element analyzed was calculated. The mineralogical composition of sediment samples and cores were obtained by X-ray diffraction. Moreover, data of orbital remote sensing were used in order to detect and quantify suspended matter by applying a logarithmic algorithm. Geochemical data of bottom sediments and cores revealed that, excepting Ba and Pb, the elements analyzed presented concentrations characteristic of an unpolluted ecosystem (Al: 0,25 - 8,76 %; Ba: 3,03 - 870 µg.g-1; Cd: < 0,25 µg.g-1; Cr: 1,72 - 82,4 µg.g-1; Cu: 0,12 -25,3 µg.g-1; Pb: 0,38 - 23,7 µg.g-1; Fe: 0,10 - 5,82 %; Mn: 15,1 - 815 µg.g-1; Ni: 0,14 - 36,1 µg.g-1; Zn: 1,37 - 113 µg.g-1). During the dry season a distribution pattern was observed, with higher metal concentrations in the margins, decreasing toward the central portion of the channel. These metal concentrations were well correlated with mineralogical compositions, with clay minerals prevailing at the margins, and quartz and feldspar in the center. However, this pattern was not observed during the wet season, probably because of the high water flux that disturbed bottom sediments. But, as observed for the dry season, a good correlation between metal concentrations and mineralogical composition was also observed for the wet season, with high metal concentrations where there were high quantities of clay minerals. Low enrichment ratios were obtained for the majority of elements analyzed, excepting for Mn, Ba and Pb. Manganese presented the higher ratios downstream for both seasons, and it can be an evidence of anthropogenic impact by shrimp farming. As barium and lead concentrations in sediment samples presented analytical problems during the total sample digestion, one cannot be sure that the ratios obtained correspond to the reality. The highest metal concentrations in particulate matter were obtained in the portion dominated by fluvial transport for all metals analyzed, excepting for copper. Barium and zinc were the only elements that presented elevated concentrations that are not common of unpolluted ecosystems (Ba: 5730 - 8355 µg.g-1; Zn: 3899 - 4348 µg.g-1). However, these high concentrations could not be related to the shrimp farming and waste waters from the town of Canguaretama, once they were obtained from the fluvial particulate matter, that is upstream from the activities above mentioned. The application of the logarithmic algorithm to the processed LANDSAT image was well succeeded, although the acquired image does not correspond exactly to the field campaigns. The IKONOS image provided very detailed views of the suspended sediment concentration at the estuary, as the mixture of distinct water flows at the confluence of Cunhaú and Curimataú rivers, with more turbid waters from Cunhaú river, that is directly affected by effluents from shrimp farming and urban waste waters deriving from the town of Canguaretama

Caracterização Morfodinâmica e Sedimentologia da Plataforma Continental Rasa na APA Estadual dos Recifes de Corais - RN

This study had to aimed to characterize the sediments of shallow continental shelf and realize the mapping of features visible for satellite images by using remote sensing techniques, digital image processing and analysis of bathymetry between Maxaranguape and Touros - RN. The study s area is located in the continental shallow shelf of Rio Grande do Norte, Brazil, and is part of the Environmental Protection Area (APA) of Coral Reefs. A total of 1186 sediment samples were collected using a dredge type van veen and positioning of the vessel was made out with the aid of a Garmin 520s. The samples were treated In the laboratory to analyze particle size of the sediment, concentration of calcium carbonate and biogenic composition. The digital images from the Landsat-5 TM were used to mapping of features. This stage was used the band 1 (0,45-1,52 μm) where the image were georeferenced, and then adjusting the histogram, giving a better view of feature bottom and contacts between different types of bottom. The results obtained from analysis of the sediment showed that the sediments of the continental shelf east of RN have a dominance of carbonate facies and a sand-gravelly bottom because the region is dominated by biogenic sediments, that are made mainly of calcareous algae. The bedform types identified and morphological features found were validated by bathymetric data and sediment samples examined. From the results obtained a division for the shelf under study is suggested, these regions being subdivided, in well characterized: (1) Turbid Zone, (2) Coral Patch Reefs Zone, (3) Mixed Sediments Carbonates Zone, ( 4) Algae Fouling Zone, (5) Alignment Rocky Zone, (6) Sand Waves Field (7) Deposit siliciclastic sands

Characterization of Soil Surface Roughness Effects on Runoff and Soil Erosion Rates under Simulated Rainfall

This study aims at identifying the influence of soil surface roughness from small to large aggregates (random roughness) on runoff and soil loss and to investigate the interaction with soil surface seal formation. Bulk samples of a silty clay loam soil were sieved to four aggregate-size classes of 3 to 12, 12 to 20, 20 to 45, 45 to 100 mm, and packed in soil trays set at a 5% slope. Rainfall simulations using an oscillating nozzle simulator were conducted for 90 min at an average rainfall intensity of 50.2 mm h(-1). Soil surface roughness was measured using an instantaneous profile laser scanner and surface sealing was studied by macroscopic analysis of epoxy impregnated soil samples. The rainfall simulations revealed longer times to initiate runoff with increasing soil surface roughness. For random roughness levels up to 6 mm, a decrease in final runoff rate with increasing roughness was observed. This can be attributed to a decreased breakdown of the larger roughness elements on rougher surfaces, thus keeping infiltration rate high. For a random roughness larger than 6 mm, a greater final runoff rate was observed. This was caused by the creation of a thick depositional seal in the concentrated flow areas, thus lowering the infiltration rates. Analysis of impregnated soil sample blocks confirmed the formation of a structural surface seal on smooth surfaces, whereas thick depositional seals were visible in the depressional areas of rougher surfaces. Therefore, from our observations it can be learned that soil surface roughness as formed by the presence of different aggregate sizes reduces runoff but that its effect diminishes due to aggregate breakdown and the formation of thick depositional seals in the case of rough soil surfaces. Sediment concentration increased with increasing soil surface roughness, due to runoff concentration in flow paths. Nevertheless, final soil loss rates were comparable for all soil roughness categories, indicating that random roughness is only important in influencing runoff rates and the time to initiate runoff, but not in influencing sediment export through soil loss rates.

Analysis and mathematical modeling of wave-structure interaction

The aim of this thesis, included within the THESEUS project, is the development of a mathematical model 2DV two-phase, based on the existing code IH-2VOF developed by the University of Cantabria, able to represent together the overtopping phenomenon and the sediment transport. Several numerical simulations were carried out in order to analyze the flow characteristics on a dike crest. The results show that the seaward/landward slope does not affect the evolution of the flow depth and velocity over the dike crest whereas the most important parameter is the relative submergence. Wave heights decrease and flow velocities increase while waves travel over the crest. In particular, by increasing the submergence, the wave height decay and the increase of the velocity are less marked. Besides, an appropriate curve able to fit the variation of the wave height/velocity over the dike crest were found. Both for the wave height and for the wave velocity different fitting coefficients were determined on the basis of the submergence and of the significant wave height. An equation describing the trend of the dimensionless coefficient c_h for the wave height was derived. These conclusions could be taken into consideration for the design criteria and the upgrade of the structures. In the second part of the thesis, new equations for the representation of the sediment transport in the IH-2VOF model were introduced in order to represent beach erosion while waves run-up and overtop the sea banks during storms. The new model allows to calculate sediment fluxes in the water column together with the sediment concentration. Moreover it is possible to model the bed profile evolution. Different tests were performed under low-intensity regular waves with an homogeneous layer of sand on the bottom of a channel in order to analyze the erosion-deposition patterns and verify the model results.

Catastrophic Flooding In North-Central Pennsylvania: Geomorphic Findings From The September 2011 Event And Their Significance To

Tropical Storm Lee produced 25-36 cm of rainfall in north-central Pennsylvania on September 4th through 8th of 2011. Loyalsock Creek, Muncy Creek, and Fishing Creek experienced catastrophic flooding resulting in new channel formation, bank erosion, scour of chutes, deposition/reworking of point bars and chute bars, and reactivation of the floodplain. This study was created to investigate aspects of both geomorphology and sedimentology by studying the well-exposed gravel deposits left by the flood, before these features are removed by humans or covered by vegetation. By recording the composition of gravel bars in the study area and creating lithofacies models, it is possible to understand the 2011 flooding. Surficial clasts on gravel bars are imbricated, but the lack of imbrication and high matrix content of sediments at depth suggests that surface imbrication of the largest clasts took place during hyperconcentrated flow (40-70% sediment concentration). The imbricated clasts on the surface are the largest observed within the bars. The lithofacies recorded are atypical for mixed-load stream lithofacies and more similar to glacial outburst flood lithofacies. This paper suggests that the accepted lithofacies model for mixed-load streams with gravel bedload may not always be useful for interpreting depositional systems. A flume study, which attempted to duplicate the stratigraphy recorded in the field, was run in order to better understand hyperconcentrated flows in the study area. Results from the study in the Bucknell Geology Flume Laboratory indicate that surficial imbrication is possible in hyperconcentrated conditions. After flooding the flume to entrain large amounts of sand and gravel, deposition of surficially imbricated gravel with massive or upward coarsening sedimentology occurred. Imbrication was not observed at depth. These experimental flume deposits support our interpretation of the lithofacies discovered in the field. The sizes of surficial gravel bar clasts show clear differences between chute and point bars. On point bars, gravels fine with increasing distance from the channel. Fining also occurs at the downstream end of point bars. In chute deposits, dramatic fining occurs down the axis of the chute, and lateral grain sizes are nearly uniform. Measuring the largest grain size of sandstone clasts at 8-11 kilometer intervals on each river reveals anomalies in the downstream fining trends. Gravel inputs from bedrock outcrops, tributaries, and erosion of Pleistocene outwash terraces may explain observed variations in grain size along streams either incised into the Appalachian Plateau or located near the Wisconsinan glacial boundary. Atomic Mass Spectrometry (AMS) radiocarbon dating of sediment from recently scoured features on Muncy Creek and Loyalsock Creek returned respective ages of 500 BP and 2490 BP. These dates suggest that the recurrence interval of the 2011 flooding may be several hundred to several thousand years. This geomorphic interval of recurrence is much longer then the 120 year interval calculated by the USGS using historical stream gauge records.

Sliding of Ice Past an Obstacle at Engabreen, Norway

At Engabreen, Norway, an instrumented panel containing a decimetric obstacle was mounted flush With the bed surface beneath 210 m of ice. Simultaneous measurements of normal and shear stresses, ice velocity and temperature were obtained as dirty basal ice flowed past the obstacle. Our measurements were broadly consistent with ice thickness, flow conditions and bedrock topography near the site of the experiment. Ice speed 0.45 m above the bed was about 130 mm d(-1), much less than the surface velocity of 800 mm d(-1) Average normal stress on the panel was 1.0-1.6 MPa, smaller than the expected ice overburden pressure. Normal stress was larger and temperature was lower on the stoss side than on the lee side, in accord with flow dynamics and equilibrium thermodynamics. Annual differences in normal stresses were correlated with changes in sliding speed and ice-flow direction. These temporal variations may have been caused by changes in ice rheology associated with changes in sediment concentration, water content or both. Temperature and normal stress were generally correlated, except when clasts presumably collided with the panel. Temperature gradients in the obstacle indicated that regelation was negligible, consistent with the obstacle size. Melt rate was about 10% of the sliding speed. Despite high sliding speed, no significant ice/bed separation was observed in the lee of the obstacle. Frictional forces between sediment particles in the ice and the panel, estimated from Hallet's (1981) model, indicated that friction accounted for about 5% of the measured bed-parallel force. This value is uncertain, as friction theories are largely untested. Some of these findings agree with sliding theories, others do not.

Settling velocity of sediments at high concentrations

New data on the settling velocity of artificial sediments and natural sands at high concentrations are presented. The data are compared with a widely used semiempirical Richardson and Zaki equation (Trans. Inst. Chem. Eng. 32 (1954) 35), which gives an accurate measure of the reduction in velocity as a function of concentration and an experimentally determined empirical power n. Here, a simple method of determining n is presented using standard equations for the clear water settling velocity and the seepage flow within fixed sediment beds. The resulting values for n are compared against values derived from new and existing laboratory data for beach and filter sands. For sands, the appropriate values of n are found to differ significantly from those suggested by Richardson and Zaki for spheres, and are typically larger, corresponding to a greater reduction in settling velocity at high concentrations. For fine and medium sands at concentrations of order 0.4, the hindered settling velocity reduces to about 70% of that expected using values of n derived for spheres. At concentrations of order 0.15, the hindered settling velocity reduces to less than half of the settling velocity in clear water. These reduced settling velocities have important implications for sediment transport modelling close to, and within, sheet flow layers and in the swash zone.

Desenvolvimento e caracterização de sensores óticos de qualidade de líquidos

A necessidade de controlar de forma rápida, eficaz e precisa a qualidade de líquidos, principalmente a água, um bem essencial para os seres humanos, conduziu ao desenvolvimento de dispositivos capazes de relacionar a medição de parâmetros físicos com a qualidade da água. Estes dispositivos devem ser capazes de monitorizar os inúmeros parâmetros necessários para aferir a qualidade do líquido, como a turvação, índice de refração, concentração de sedimentos e propriedades cromáticas. Desta forma devem-se recorrer a sensores multiparâmetros. A tecnologia baseada em POF (fibra ótica polimérica) tem sido apontada com elevado potencial no desenvolvimento de sensores óticos nas mais variadas aplicações dado o seu baixo custo, imunidade a interferências eletromagnéticas e flexibilidade. Neste trabalho é proposto um sensor POF multiparâmetro capaz de reunir num único dispositivo a capacidade de medição de altos e baixos valores de turvação, assim como ter a capacidade de medir vários parâmetros em simultâneo e em tempo real. Os resultados permitem avaliar o aumento da capacidade de gama dinâmica de turvação e concentração de sedimentos face aos sensores multiparâmetros já comercializados, uma vez que houve uma boa resposta por parte do sensor para altos e para baixos valores. Um método utilizado para descorrelacionar os diferentes parâmetros foi aplicado com sucesso. A WATGRID LDA. pretende, partindo deste tipo de sensores, disponibilizar aos seus clientes soluções (plataformas) inteligentes e integradas para avaliação e gestão da qualidade dos líquidos para consumo (e.g. água e vinho). Estas soluções irão permitir que os clientes da WATGRID LDA. aumentem a sua eficiência, a qualidade do seu produto e tenham um maior controlo do processo ao mesmo tempo que reduzem custos.

Pelagic molybdenum concentration anomalies and the impact of sediment resuspension on the molybdenum budget in two tidal systems of the North Sea

The seasonal dynamics of molybdenum (Mo) were studied in the water column of two tidal basins of the German Wadden Sea (Sylt-Rømø and Spiekeroog) between 2007 and 2011. In contrast to its conservative behaviour in the open ocean, both, losses of more than 50% of the usual concentration level of Mo in seawater and enrichments up to 20% were observed repeatedly in the water column of the study areas. During early summer, Mo removal by adsorption on algae-derived organic matter (e.g. after Phaeocystis blooms) is postulated to be a possible mechanism. Mo bound to organic aggregates is likely transferred to the surface sediment where microbial decomposition enriches Mo in the pore water. First δ98/95Mo data of the study area disclose residual Mo in the open water column being isotopically heavier than MOMo (Mean Ocean Molybdenum) during a negative Mo concentration anomaly, whereas suspended particulate matter shows distinctly lighter values. Based on field observations a Mo isotope enrichment factor of ε = −0.3‰ has been determined which was used to argue against sorption on metal oxide surfaces. It is suggested here that isotope fractionation is caused by biological activity and association to organic matter. Pelagic Mo concentration anomalies exceeding the theoretical salinity-based concentration level, on the other hand, cannot be explained by replenishment via North Sea waters alone and require a supply of excess Mo. Laboratory experiments with natural anoxic tidal flat sediments and modelled sediment displacement during storm events suggest fast and effective Mo release during the resuspension of anoxic sediments in oxic seawater as an important process for a recycling of sedimentary sulphide bound Mo into the water column.

Methane concentration in sediment cores during METEOR cruise M92

We studied the concurrence of methanogenesis and sulfate reduction in surface sediments (0-25 cm below sea floor, cmbsf) at six stations (70, 145, 253, 407, 770 and 1024 m) along the Peruvian margin (12° S). This oceanographic region is characterized by high carbon export to the seafloor, creating an extensive oxygen minimum zone (OMZ) on the shelf, both factors that could favor surface methanogenesis. Sediments sampled along the depth transect traversed areas of anoxic and oxic conditions in the bottom-near water. Net methane production (batch incubations) and sulfate reduction (35S-sulfate radiotracer incubation) were determined in the upper 0-25 cmbsf of multicorer cores from all stations, while deep hydrogenotrophic methanogenesis (> 30 cmbsf, 14C-bicarbonate radiotracer incubation) was determined in two gravity cores at selected sites (78 and 407 m). Furthermore, stimulation (methanol addition) and inhibition (molybdate addition) experiments were carried out to investigate the relationship between sulfate reduction and methanogenesis. Highest rates of methanogenesis and sulfate reduction in the surface sediments, integrated over 0-25 cmbsf, were observed on the shelf (70-253 m, 0.06-0.1 and 0.5-4.7 mmol m-2 d-1, respectively), while lowest rates were discovered at the deepest site (1024 m, 0.03 and 0.2 mmol m-2 d-1, respectively). The addition of methanol resulted in significantly higher surface methanogenesis activity, suggesting that the process was mostly based on non-competitive substrates, i.e., substrates not used by sulfate reducers. In the deeper sediment horizons, where competition was probably relieved due to the decline of sulfate, the usage of competitive substrates was confirmed by the detection of hydrogenotrophic activity in the sulfate-depleted zone at the shallow shelf station (70 m). Surface methanogenesis appeared to be correlated to the availability of labile organic matter (C / N ratio) and organic carbon degradation (DIC production), both of which support the supply of methanogenic substrates. A negative correlation of methanogenesis rates with dissolved oxygen in the bottom-near water was not obvious, however, anoxic conditions within the OMZ might be advantageous for methanogenic organisms at the sediment-water interface. Our results revealed a high relevance of surface methanogenesis on the shelf, where the ratio between surface to deep (below sulfate penetration) methanogenic activity ranged between 0.13 and 105. In addition, methane concentration profiles indicate a partial release of surface methane into the water column as well as a partial consumption of methane by anaerobic methane oxidation (AOM) in the surface sediment. The present study suggests that surface methanogenesis might play a greater role in benthic methane budgeting than previously thought, especially for fueling AOM above the sulfate-methane transition zone.

Element concentration and GDGT fractional abundances of sediment core GeoB3910-2

In dieser Arbeit wurde das Zeitintervall zwischen 20 und 10 ka vor heute einschließlich des Heinrichevent 1 und der Younger Dryas am Kern GeoB 3910-2 neu untersucht. An organischen Parametern, basierend auf der Verteilung von bakteriellen GDGTs, und Elementkonzentrationen wurde eine Rekonstruktion der klimatischen Bedingungen und Veränderungen im Hinterland von NO Brasilien durchgeführt. Es zeigt sich, dass sich die durchschnittliche Landtemperatur gleich der Oberflächenwassertemperatur verhält und im Gegensatz zu den Phasen von H6 bis H2 dem antarktischen Erwärmungstrend ab 17 ka vor heute folgt. Weiterhin konnte gezeigt werden, dass durch die südwärts Verlagerung der ITCZ während H1 und der YD die Niederschläge in NO Brasilen intensiviert wurden, was eine Ausbreitung der Flüsse und Änderung der Erosionsgebiete zur Folge hatte.