Fluid–Rock Interactions in Geothermal Reservoirs,Germany: Thermal Autoclave Experiments Using Sandstones and Natural Hydrothermal Brines     

Schäffer  Rafael  Götz  Emilia  Schlatter  Nils  Schubert  Gabriela  Weinert  Sebastian  Schmidt  Stefanie  Kolb  Ute  Sass  Ingo 《Aquatic Geochemistry》2022,28(2):63-110

As renewable energy, geothermal can contribute substantially to the energy transition. To generate electricity or to harvest heat, high-saline fluids are tapped by wells of a few kilometres and extracted from hydrothermal reservoirs. After the heat exchanger units have been passed by, these fluids are reinjected into the reservoir. Due to the pressure and temperature differences between the subsurface and the surface, as well as the cooling of the fluids in the power plant, unwanted chemical reactions can occur within the reservoir, in the borehole, and within the power plant itself. This can reduce the permeability of the reservoir as well as the output of the geothermal power plant. This study aims to simulate real subsurface reactions using batch and leaching experiments with sandstone or sandstone powder as solid phase, and deionised water or natural brine as liquid phase. It is demonstrated that fluid composition changes after only a few days. In particular, calcite, aragonite, clay minerals, and zinc phases precipitate from the natural brine. In contrast, in particular minerals containing potassium, arsenic, barium, and silica are dissolved. Due to the experimental set-up, these mineral reactions mainly took place on the surface of the samples, which is why no substantial changes in petrophysical properties could be observed. However, it is assumed that the observed reactions on the reservoir scale have a relevant influence on parameters such as permeability.

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Geology,permafrost, and lake level changes as factors initiating landslides on Olkhon Island (Lake Baikal,Siberia)     

Sebastian Tyszkowski  Halina Kaczmarek  Michał Słowiński  Elena Kozyreva  Dariusz Brykała  Artiom Rybchenko  Viktoria A. Babicheva 《Landslides》2015,12(3):573-583

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Carbonate drifts as marine archives of aeolian dust (Santaren Channel,Bahamas)     

Sebastian Lindhorst  Christian Betzler  Marco Wunsch  Thomas Lüdmann  Gerhard Kuhn 《Sedimentology》2019,66(4):1386-1409

Sediment data from the Bahamian Santaren carbonate drift reveal the variability of trans‐Atlantic Saharan dust transport back to about 100 ka bp (Marine Isotope Stage 5·3) and demonstrate that carbonate drifts are a valuable pelagic archive of aeolian dust flux. Carbonate drift bodies are common around tropical carbonate platforms; they represent large‐scale accumulations of ocean‐current transported material, which originates from the adjacent shallow‐water carbonate factory as well as from pelagic production, i.e. periplatform ooze. Subordinately, there is a clay‐size to silt‐size non‐carbonate fraction, which typically amounts to less than 10% of the sediment volume and originates from aeolian and fluvial input. Sedimentation rates in the 5·42 m long core GeoHH‐M95‐524 recovered 25 km west of Great Bahama Bank in the Santaren Channel ranges from 1·5 to 24·5 cm ka^?1 with lowest values during the last glacial lowstand and highest values following platform re‐flooding around 8 ka bp . These sedimentation rates imply that carbonate drifts have not only the potential to resolve long‐term environmental changes on orbital timescales, but also millennial to centennial fluctuations during interglacials. The sediment core has been investigated with the aim of characterizing the lithogenic dust fraction. Laboratory analyses included X‐ray fluorescence core scanning, determination of carbonate content and grain‐size analyses (of bulk and terrigenous fraction), as well as visual inspections of the lithogenic residue; the age model is based on oxygen isotopes and radiocarbon ages. Data show that the input of aeolian dust in the periplatform ooze as indicated by Ti/Al and Fe/Al element ratios abruptly increases at 57 ka bp , stays elevated during glacial times, and reaches a Holocene minimum around 6·5 ka bp , contemporary to the African Humid Period. Subsequently, there is a gradual increase in dust flux which almost reaches glacial levels during the last centuries. Grain‐size data show that the majority of dust particles fall into the fine silt range (below 10 μm); however, there is a pronounced coarse dust fraction in the size range up to 63 μm and individual ‘giant’ dust particles are up to 515 μm in size. Total dust flux and the relative amounts of fine and coarse dust are decoupled. The time‐variable composition of the grain‐size spectrum is interpreted to reflect different dust transport mechanisms: fine dust particles are delivered by the trade winds and the geostrophic winds of the Saharan Air Layer, whereas coarse dust particles travel with convective storm systems. This mode of transport ensures continuous re‐suspension of large particles and results in a prolonged transport. In this context, grain‐size data from the terrigenous fraction of carbonate drifts provide a measure for past coarse dust transport, and consequently for the frequency of convective storm systems over the dust source areas and the tropical Atlantic.  相似文献   

Lack of association between color morphs of the Jellyfish Cassiopea andromeda and zooxanthella clade     

Kathrin P. Lampert  Patrick Bürger  Sebastian Striewski  Ralph Tollrian 《Marine Ecology》2012,33(3):364-369

Understanding the ecology and evolution of the cnidarian-algal symbiosis is of major scientific interest as it is sensitive to temperature and strong light and may therefore be susceptible to climate change. The stability of this mutualism is often mediated by host color pigments that influence photosynthetic activity in symbiotic dinoflagellates either by providing the photosystem with irradiance of suitable wavelength or by protecting it from much too much and potentially damaging light. Like scleractinian corals, the upside-down jellyfish, Cassiopea andromeda, relies heavily on the nutrients provided by its symbionts of the dinoflagellate genus Symbiodinium. It occurs in several conspicuously different color morphs and is found in habitats with high levels of irradiation. We tested whether the color morphs of Cassiopea were correlated with the Symbiodinium distribution in the host and whether host color was associated with different clades of Symbiodinium. We found that the presence of color pigment did not correlate with the distribution of Symbiodinium in the host. Symbiodinium was found in both the colored tentacles of the jellyfish and the colorless feeding tentacles. At least six different color morphs co-occurred in the very shallow waters of the Red Sea, but they all hosted a single Symbiodinium clade (clade A1). Therefore, no correlation of host color morph and Symbiodinium clade could be found. Photoaccumulative or photoprotective functions of host pigments, as proposed for some scleractinian corals, thus seem unlikely in the colored tentacles (vesicles) of the upside-down jellyfish Cassiopea andromeda.  相似文献   

A Recent Shellfish Toxin Investigation in China   总被引：30，自引：0，他引：30  

Mingjiang Zhou  Jun Li  Bernd Luckas  Rencheng Yu  Tian Yan  Christian Hummert  Sebastian Kastrup 《Marine pollution bulletin》1999,39(1-12):331-334

A shellfish toxin investigation along the Chinese coast has recently been conducted using both HPLC and mouse assay methods. The results showed that DSP was widely distributed in different shellfish species in China. 26 out of 89 samples had DTX1 (dinophysistoxin-1) or OA (okadaic acid) but the DSP content in most shellfish samples did not reach the regulatory limit for human consumption adopted in many countries (20 μg/100 g soft tissue). PSP was also found in 5 out of 96 samples along the coast. One sample, Chlamys nobilis from Hong Kong contained high levels of PSP (320 μg STX equivalent/100 g soft tissue), compared to the regulatory limit (80 μg STX equivalent/100 g soft tissue). After the recent outbreak of red tide in Hong Kong waters, three further shellfish samples were collected within 40 days to investigate the impacts of this event. It was shown that high levels of PSP continued to exist in Hong Kong waters. This report provides the first report of DSP and PSP distribution along the Chinese coast.  相似文献   

Nordic Landscapes: Region and Belonging on the Northern Edge of Europe – Edited by Michael Jones and Kenneth R Olwig
The Nordic Model: Scandinavia since 1945 – By Mary Hilson     

Sebastian  Eiter 《The Geographical journal》2009,175(4):320-321

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The influence of great earthquakes on volcanic eruption rate along the Chilean subduction zone     

Sebastian F.L. Watt  David M. Pyle  Tamsin A. Mather 《Earth and Planetary Science Letters》2009,277(3-4):399-407

Seismic activity has been postulated as a trigger of volcanic eruption on a range of timescales, but demonstrating the occurrence of triggered eruptions on timescales beyond a few days has proven difficult using global datasets. Here, we use the historic earthquake and eruption records of Chile and the Andean southern volcanic zone to investigate eruption rates following large earthquakes. We show a significant increase in eruption rate following earthquakes of M_W > 8, notably in 1906 and 1960, with similar occurrences further back in the record. Eruption rates are enhanced above background levels for ~ 12 months following the 1906 and 1960 earthquakes, with the onset of 3–4 eruptions estimated to have been seismically influenced in each instance. Eruption locations suggest that these effects occur from the near-field to distances of ~ 500 km or more beyond the limits of the earthquake rupture zone. This suggests that both dynamic and static stresses associated with large earthquakes are important in eruption-triggering processes and have the potential to initiate volcanic eruption in arc settings over timescales of several months.  相似文献   

Health, sustainability and equity: global trade in the brave new world     

Carolyn Stephens  Simon Lewin  Giovanni Leonardi  Miguel San Sebastian Chasco  Richard Shaw 《Global Change & Human Health》2000,1(1):44-58

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Drought and its effects on spring discharge regimes in Poland and Germany during the 2015 drought     

Stanisław Staśko  Sebastian Buczyński 《水文科学杂志》2018,63(5):741-751

Areas of Western and Central Europe were severely affected by devastating droughts in 2003 and 2015. A sharp decrease in annual atmospheric precipitation led to diminished spring discharges. Analysis of the fluctuations in discharge from three groups of springs in the south of Poland, namely in the Sudetes and Carpathian mountains, and in the German province of Bavaria revealed an average discharge reduction ranging from 52 to 4%. The study proved the existence of a relationship between diminished groundwater recharge from precipitation and the type of rock forming the reservoir as well as the parameters of the rock in the drained catchment. Spring discharge regime was compared for various periods to show that a decline in the regime correlates with a decline in river flow rate; considering the continually changing weather patterns, this correlation is arguably a key factor in sustainable water management.  相似文献   

Robustness of simplified analysis methods for rocking structures on compliant soil     

Max Sieber  Sebastian Klar  Michalis F. Vassiliou  Ioannis Anastasopoulos 《地震工程与结构动力学》2020,49(14):1388-1405

Recognizing the beneficial effect of nonlinear soil–foundation response has led to a novel design concept, termed ‘rocking isolation’. The analysis and design of such rocking structures require nonlinear dynamic time history analyses. Analyzing the entire soil–foundation–structure system is computationally demanding, impeding the application of rocking isolation in practice. Therefore, there is an urgent need to develop efficient simplified analysis methods. This paper assesses the robustness of two simplified analysis methods, using (i) a nonlinear and (ii) a bilinear rocking stiffness combined with linear viscous damping. The robustness of the simplified methods is assessed by (i) one-to-one comparison with a benchmark finite element (FE) analysis using a selection of ground motions and (ii) statistical comparison of probability distributions of response quantities, which characterize the time history response of rocking systems. A bridge pier (assumed rigid) supported on a square foundation, lying on a stiff clay stratum, is used as an illustrative example. Nonlinear dynamic FE time history analysis serves as a benchmark. Both methods yield reasonably accurate predictions of the maximum rotation θ_max. Their stochastic comparison with respect to the empirical cumulative distribution function of θ_max reveals that the nonlinear and the bilinear methods are not biased. Thus, both can be used to estimate probabilities of exceeding a certain threshold value of θ. Developed in this paper, the bilinear method is much easier to calibrate than the nonlinear, offering similar performance.  相似文献