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Eva Leitholdt Christoph Zielhofer Stefanie Berg‐Hobohm Katharina Schnabl Britta Kopecky‐Hermanns Jens Bussmann Joachim W. Hrtling Klaus Reicherter Katrin Unger 《Geoarchaeology》2012,27(1):88-104
The Central European watershed passes through the southern Franconian Jura in Bavaria, Germany. This principal watershed divides the Rhine/Main catchment and the Danube catchment. In the early Middle Ages, when ships were an important means of transportation, Charlemagne decided to connect these catchments by the construction of a canal known as the Fossa Carolina. In this paper, we present for the first time 14C data from the Fossa Carolina fill and document a high‐resolution stratigraphic record of the Carolingian and post‐Carolingian trench infilling. Our results provide clear evidence for peat layers in different levels of the trench infill, suggesting a chain of ponds. However, the majority of these peat layers yield mid‐Medieval and younger ages. The period of major peat growth was during the Medieval climatic optimum. Therefore, our preliminary results do not prove the use of the trench during Carolingian times. However, first results from the reconstruction of the Carolingian trench bottom support the hypothesis that the Fossa was primarily planned as a navigable chain of ponds and not as a continuous canal. In the eastern part of the trench, a dam is located that was postulated in former studies to be part of a barrage for supplying the Carolingian canal with water. New 14C data indicate much younger ages and do not support the Carolingian barrage concept. 相似文献
44.
Dedong Li Sebastian Bauer Katharina Benisch Bastian Graupner Christof Beyer 《Acta Geotechnica》2014,9(1):67-79
Sequestration of CO2 into a deep geological reservoir causes a complex interaction of different processes such as multiphase flow, phase transition, multicomponent transport, and geochemical reactions between dissolved CO2 and the mineral matrix of the porous medium. A prognosis of the reservoir behaviour and the feedback from large-scale geochemical alterations require efficient process-based numerical models. For this purpose, the multiphase flow and multicomponent transport code OpenGeoSys-Eclipse have been coupled to the geochemical model ChemApp. The newly developed coupled simulator was successfully verified for correctness and accuracy of the implemented reaction module by benchmarking tests. The code was then applied to assess the impact of geochemical reactions during CO2 sequestration at a hypothetical but typical Bunter sandstone formation in the Northern German Basin. Injection and spreading of 1.48 × 107 t of CO2 in an anticline structure of the reservoir were simulated over a period of 20 years of injection plus 80 years of post-injection time. Equilibrium geochemical calculations performed by ChemApp show only a low reactivity to the geochemical system. The increased acidity of the aqueous solution results in dissolution of small amounts of calcite, anhydrite, and quartz. Geochemical alterations of the mineral phase composition result in slight increases in porosity and permeability, which locally may reach up to +0.02 and 0.1 %, respectively. 相似文献
45.
Schubert H Feuerpfeil P Marquardt R Telesh I Skarlato S 《Marine pollution bulletin》2011,62(9):1948-1956
Remane’s species-minimum concept, which states that the lowest number of taxa occurs at the horohalinicum (5-8 psu), was tested by investigating macroalgal diversity on hard substrates along the natural salinity gradient in the Baltic Sea. Field data on species occurrence and abundance were collected by SCUBA diving along 10 transects of the Finnish, Swedish and German coasts, covering a salinity range from 3.9 to 27 psu. Macroalgal species numbers declined steadily with salinity, decreasing until 7.2 psu was reached, but in the horohalinicum, a marked reduction of species number and a change in diversity were indicated by the Shannon index and evenness values. The non-linear decrease in macroalgal diversity at 5-8 psu and the lack of increase in species numbers at salinities below 5 psu imply a restricted applicability of Remane’s species-minimum concept to macroalgae. 相似文献
46.
Oliver Montenbruck André Hauschild Yago Andres Axel von Engeln Christian Marquardt 《GPS Solutions》2013,17(2):199-209
The processing of GPS radio occultation measurements for use in numerical weather predictions requires a precise orbit determination (POD) of the host satellite in near-real-time. Making use of data from the GRAS instrument on Metop-A, the performance of different GPS ephemeris products and processing concepts for near-real-time and real-time POD is compared. While previous analyses have focused on the achievable along-track velocity accuracy, this study contributes a systematic comparison of the resulting estimated bending angles. This enables a more rigorous trade-off of different orbit determination methodologies in relation to the end-user needs for atmospheric science products. It is demonstrated that near-real-time GPS orbit and clock products have reached a sufficient quality to determine the Metop-A along-track velocity with an accuracy of better than 0.05 mm/s that was formerly only accessible in post-processing. The resulting bending angles are shown to exhibit standard deviation and bias differences of less than 0.3 % compared with post-processed products up to altitudes of at least 40 km, which is notably better than 1 % accuracy typically assumed for numerical weather predictions in this height regime. Complementary to the analysis of ground-based processing schemes, the potential of autonomous on-board orbit determination is investigated for the first time. Using actual GRAS flight data, it is shown that a 0.5 m 3D rms position accuracy and a 0.2 mm/s along-track velocity accuracy can in fact be obtained in real-time with the currently available GPS broadcast ephemeris quality. Bending angles derived from the simulated real-time processing exhibit a minor performance degradation above tangent point heights of 40 km but negligible differences with respect to ground-based products below this altitude. Onboard orbit determination and, if desired, bending angle computation, can thus enable a further simplification of the ground segment in future radio occultation missions and contribute to reduced product latencies for radio occultation data assimilation in numerical weather predictions. 相似文献
47.
Bayden D. Russell Sean D. Connell Sven Uthicke Nancy Muehllehner Katharina E. Fabricius Jason M. Hall-Spencer 《Marine pollution bulletin》2013
While carbon capture and storage (CCS) is increasingly recognised as technologically possible, recent evidence from deep-sea CCS activities suggests that leakage from reservoirs may result in highly CO2 impacted biological communities. In contrast, shallow marine waters have higher primary productivity which may partially mitigate this leakage. We used natural CO2 seeps in shallow marine waters to assess if increased benthic primary productivity could capture and store CO2 leakage in areas targeted for CCS. We found that the productivity of seagrass communities (in situ, using natural CO2 seeps) and two individual species (ex situ, Cymodocea serrulata and Halophila ovalis) increased with CO2 concentration, but only species with dense belowground biomass increased in abundance (e.g. C. serrulata). Importantly, the ratio of below:above ground biomass of seagrass communities increased fivefold, making seagrass good candidates to partially mitigate CO2 leakage from sub-seabed reservoirs, since they form carbon sinks that can be buried for millennia. 相似文献
48.
Melanie Shaw Miles J. Furnas Katharina Fabricius David Haynes Steve Carter Jochen F. Mueller 《Marine pollution bulletin》2010,60(1):113-122
Pesticide runoff from agriculture poses a threat to water quality in the world heritage listed Great Barrier Reef (GBR) and sensitive monitoring tools are needed to detect these pollutants. This study investigated the utility of passive samplers in this role through deployment during a wet and dry season at river mouths, two near-shore regions and an offshore region. The nearshore marine environment was shown to be contaminated with pesticides in both the dry and wet seasons (average water concentrations of 1.3-3.8 ng L−1 and 2.2-6.4 ng L−1, respectively), while no pesticides were detected further offshore. Continuous monitoring of two rivers over 13 months showed waters flowing to the GBR were contaminated with herbicides (diuron, atrazine, hexazinone) year round, with highest average concentrations present during summer (350 ng L−1). The use of passive samplers has enabled identification of insecticides in GBR waters which have not been reported in the literature previously. 相似文献
49.
Jenő Reiczigel Katharina Brugger Franz Rubel Norbert Solymosi Zsolt Lang 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):455-462
The Usutu virus is an arbovirus transmitted by mosquitoes and causing disease in birds. The virus was detected in Austria
for the first time in 2001, while a major outbreak occurred in 2003. Rubel et al. (2008) developed a nine-compartment deterministic SEIR model to explain the spread of the disease. We extended this to a hierarchical
Bayes model assuming random variation in temperature data, in reproduction data of birds, and in the number of birds found
to be infected. The model was implemented in R, combined with the FORTRAN subroutine for the original deterministic model.
Analysis was made by MCMC using a random walk Metropolis scheme. Posterior means, medians, and credible intervals were calculated
for the parameters. The hierarchical Bayes approach proved to be fruitful in extending the deterministic model into a stochastic
one. It allowed for Bayesian point and interval estimation and quantification of uncertainty of predictions. The analysis
revealed that some model parameters were not identifiable; therefore we kept constant some of them and analyzed others conditional
on them. Identifiability problems are common in models aiming to mirror the mechanism of the process, since parameters with
natural interpretation are likely to exhibit interrelationships. This study illustrated that Bayesian modeling combined with
conditional analysis may help in those cases. Its application to the Usutu model improved model fit and revealed the structure
of interdependencies between model parameters: it demonstrated that determining some of them experimentally would enable estimation
of the others, except one of them, from available data. 相似文献
50.
Hauke Marquardt Steffen Ganschow Frank R. Schilling 《Physics and Chemistry of Minerals》2009,36(2):107-118
Knowledge of heat transport properties as a function of mineral- and rock-composition and temperature is of major relevance
to understand and model heat transfer in the Earth’s interior. A systematic study on 13 natural and 4 synthetic garnets was
carried out in an attempt to obtain a better systematic understanding of the processes that affect the heat transport in minerals,
especially the effect of chemical substitution in solid solution series. It is found that substitution significantly lowers
the thermal diffusivity from end-member values for both synthetic and natural garnets with a minimum of thermal diffusivity
at an intermediate composition. The thermal diffusivity as a function of the degree of substitution can be described by the
approach of Padture and Klemens (J Am Ceram Soc 80 (4):1018–1020, 1997). With increasing temperature the thermal diffusivity decreases due to phonon-phonon-scattering effects. A quantitative analysis
of the high-temperature behaviour was carried out by using the model of Roufosse and Klemens (J Geophys Res 79 (5):703–705,
1974), which takes a lower limit of thermal diffusivity at elevated temperatures into account. The model allows for an extrapolation
of the deduced room temperature thermal diffusivities to higher temperatures. Furthermore, the model was modified to determine
the high temperature limit of the thermal diffusivity for all investigated natural garnets D
min to be 0.64 ± 0.03 mm2/s. 相似文献