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61.
The impact of low water periods on inland navigation and companies is well known by ship-operators and companies that rely on this mode of transport but it is rarely a topic of climate impact research. As climate change might affect the frequency and intensity of low water periods, quantifying the impact of climate change on companies and the effects of possible adaptation measures is vital. In this study, we present a model for quantifying the impact of low water events on companies which rely on inland navigation and apply that model to three anonymous iron and steel companies along the River Rhine. The deviation of optimal storage, the storage level that evens out risk vs. fixed capital, is used in the model to measure the vulnerability of companies. The results show that, depending on the climate scenario, the companies might have to deal with either one or five additional days of empty storage in the near future (2021–2050) and up to nine more days by the 2071–2100 period. Seasonal analysis shows that, consistent with the change in the river discharge, the biggest deviations from optimal storage level occur in the late summer/early autumn. Analysis of adaptation options shows that companies would need to increase storage capacity by 2.5 % for the 2021–2050 period, and by 25 % by the 2071–2100 period. A reduction of ship sizes is not an adaptation option for the three companies in this study, because these companies already use relatively small vessels. This is however an efficient adaptation option for companies which employ larger vessels for transport. Another adaptation option would be to reduce the share of transportation via inland waters, but the feasibility of this option depends on the availability and cost of other modes of transport. 相似文献
62.
Quantitative archaeoseismological investigation of the Great Theatre of Larissa, Greece 总被引:1,自引:0,他引:1
R. Caputo K.-G. Hinzen D. Liberatore S. Schreiber B. Helly A. Tziafalias 《Bulletin of Earthquake Engineering》2011,9(2):347-366
Larissa, the capital of Thessaly, is located in the eastern part of Central Greece, at the southern border of a Late Quarternary
graben, the Tyrnavos Basin. Palaeoseismological, morphotectonic, and geophysical investigations as well as historical and
instrumental records show evidences for seismic activity in this area. Previous investigations documented the occurrence of
several moderate to strong earthquakes during Holocene time on active faults with recurrence intervals of a few thousand years.
The historical and instrumental records suggest a period of seismic quiescence during the last 400–500 years. The present
archaeoseismological research, based on a multidisciplinary approach is devoted to improve the knowledge on past earthquakes,
which occurred in the area. This study focuses on damages observed on the walls of the scene building of the Great Theatre of Larissa. The Theatre was built at the beginning of the third century BC and consists of
a semicircular auditorium, an almost circular arena and a main scene building. Archaeological and historical investigations document a partial destruction of the theatre during the second to
first century BC. Recent excavations show that the building complex after it was repaired suffered additional structural damages,
probably from seismic loading. The damages investigated in detail are displacements, rotations and ruptures of numerous blocks
at the walls of the scene building. In order to test the earthquake hypothesis as cause of the damages a simplified seismotectonic model of the Tyrnavos
Basin and its surroundings was used with a composite earthquake source model to calculate synthetic seismograms at the Larissa
site for various earthquake scenarios. Horizontal to vertical seismic ratio (HVSR) measurements in the theatre and its vicinity
were used to estimate local site effects. The synthetic seismograms are then used as input accelerations for a finite element
model of the walls, which simulates seismically induced in-plane sliding within the walls. Results show that some of the surrounding
faults have the potential to produce seismic ground motion that can induce in-plane sliding of blocks. Model calculations
were used to constrain the characteristics of the ground acceleration and infer the causative fault and earthquake by comparing
the calculated and observed distribution of the displacements of the blocks. Ground motions with a PGA at the site of 0.62–0.82 g,
which could be induced by an M 5.8–6.0 earthquake on the nearby Larissa Fault, would be sufficient to explain the damage. 相似文献
63.
Sources of fluids and gases expelled at cold seeps offshore Georgia, eastern Black Sea 总被引:1,自引:0,他引:1
Anja Reitz Thomas Pape Mark Schmidt Florian Scholz Giovanni Aloisi Stephan M. Weise 《Geochimica et cosmochimica acta》2011,75(11):3250-46
Four seep sites located within an ∼20 km2 area offshore Georgia (Batumi seep area, Pechori Mound, Iberia Mound, and Colkheti Seep) show characteristic differences with respect to element concentrations, and oxygen, hydrogen, strontium, and chlorine isotope signatures in pore waters, as well as impregnation of sediments with petroleum and hydrocarbon potential. All seep sites have active gas seepage, near surface authigenic carbonates and gas hydrates. Cokheti Seep, Iberia Mound, and Pechori Mound are characterized by oil-stained sediments and gas seepage decoupled from deep fluid advection and bottom water intrusion induced by gas bubble release. Pechori Mound is further characterized by deep fluid advection of lower salinity pore fluids. The Pechori Mound pore fluids are altered by mineral/water reactions at elevated temperatures (between 60 and 110 °C) indicated by heavier oxygen and lighter chlorine isotope values, distinct Li and B enrichment, and K depletion. Strontium isotope ratios indicate that fluids originate from late Oligocene strata. This finding is supported by the occurrence of hydrocarbon impregnations within the sediments. Furthermore, light hydrocarbons and high molecular weight impregnates indicate a predominant thermogenic origin for the gas and oil at Pechori Mound, Iberia Mound, and Colkheti Seep. C15+ hydrocarbons at the oil seeps are allochtonous, whereas those at the Batumi seep area are autochthonous. The presence of oleanane, an angiosperm biomarker, suggests that the hydrocarbon source rocks belong to the Maikopian Formation. In summary, all investigated seep sites show a high hydrocarbon potential and hydrocarbons of Iberia Mound, Colkheti Seep, and Pechori Mound are predominantly of thermogenic origin. However, only at the latter seep site advection of deep pore fluids is indicated. 相似文献
64.
Mirko Dreßler Anja Schwarz Thomas Hübener Sven Adler Burkhard W. Scharf 《Journal of Paleolimnology》2011,45(2):223-241
Fossil diatoms from lake sediments have been used to infer both past trophic state and climate conditions. In Europe, climate
reconstructions focused on northern and alpine regions because these areas are climatically sensitive and anthropogenic impact
was low. In contrast, anthropogenic impact was often high in the central European lowlands, such as northern Germany, beginning
in the Neolithic Age, ~3700 BC. Since that time, trophic state change was the main factor that affected diatom assemblages
in central European lowland lakes. Therefore, it was considered difficult or impossible to identify climate changes in the
region using sedimented diatoms. We used diatom assemblage changes, diatom-inferred total phosphorus concentrations and the
relative abundance of planktonic diatoms from sediments of three lakes that differ in their location, size, morphology, catchment
area and current trophic state to test whether we could distinguish between trophic state and climate signals over the past
5,000 years in northern Germany. In this study, changes in trophic state and climate were well differentiated. In the study
lakes, relative abundance of planktonic diatoms seems to be linked to the length of lake mixing phases. Planktonic diatom
abundance decreased during years with shorter mixing duration, and these shorter mixing times probably reflect colder winters.
The diatom-inferred periods of short mixing phases from 1000 BC to AD 500 and from AD 1300 to 1800 coincide well with two
known cooling phases in Europe and the North Atlantic region. 相似文献
65.
66.
Michael H. POELCHAU Thomas KENKMANN Klaus THOMA Tobias HOERTH Anja DUFRESNE Frank SCHÄFER 《Meteoritics & planetary science》2013,48(1):8-22
Abstract– The MEMIN research unit (Multidisciplinary Experimental and Modeling Impact research Network) is focused on analyzing experimental impact craters and experimental cratering processes in geological materials. MEMIN is interested in understanding how porosity and pore space saturation influence the cratering process. Here, we present results of a series of impact experiments into porous wet and dry sandstone targets. Steel, iron meteorite, and aluminum projectiles ranging in size from 2.5 to 12 mm were accelerated to velocities of 2.5–7.8 km s?1, yielding craters with diameters between 3.9 and 40 cm. Results show that the target’s porosity reduces crater volumes and cratering efficiency relative to nonporous rocks. Saturation of pore space with water to 50% and 90% increasingly counteracts the effects of porosity, leading to larger but flatter craters. Spallation becomes more dominant in larger‐scale experiments and leads to an increase in cratering efficiency with increasing projectile size for constant impact velocities. The volume of spalled material is estimated using parabolic fits to the crater morphology, yielding approximations of the transient crater volume. For impacts at the same velocity these transient craters show a constant cratering efficiency that is not affected by projectile size. 相似文献
67.
68.
Interpretation of single-well tests with the Cooper-Jacob method remains more reasonable than most alternatives. Drawdowns from 628 simulated single-well tests where transmissivity was specified were interpreted with the Cooper-Jacob straight-line method to estimate transmissivity. Error and bias as a function of vertical anisotropy, partial penetration, specific yield, and interpretive technique were investigated for transmissivities that ranged from 10 to 10,000 m(2)/d. Cooper-Jacob transmissivity estimates in confined aquifers were affected minimally by partial penetration, vertical anisotropy, or analyst. Cooper-Jacob transmissivity estimates of simulated unconfined aquifers averaged twice the known values. Transmissivity estimates of unconfined aquifers were not improved by interpreting results with an unconfined aquifer solution. Judicious interpretation of late-time data consistently improved estimates where transmissivity exceeded 250 m(2)/d in unconfined aquifers. 相似文献
69.
In the Earth's upper crust, where aqueous fluids can circulate freely, most mineral transformations are controlled by the coupling between the dissolution of a mineral that releases chemical species into the fluid and precipitation of new minerals that contain some of the released species in their crystal structure, the coupled process being driven by a reduction of the total free-energy of the system. Such coupled dissolution-precipitation processes occur at the fluid-mineral interface where the chemical gradients are highest and heterogeneous nucleation can be promoted, therefore controlling the growth kinetics of the new minerals. Time-lapse nanoscale imaging using Atomic Force Microscopy (AFM) can monitor the whole coupled process under in situ conditions and allow identifying the time scales involved and the controlling parameters. We have performed a series of experiments on carbonate minerals (calcite, siderite, dolomite and magnesite) where dissolution of the carbonate and precipitation of a new mineral was imaged and followed through time. In the presence of various species in the reacting fluid (e. g. antimony, selenium, arsenic, phosphate), the calcium released during calcite dissolution binds with these species to form new minerals that sequester these hazardous species in the form of a stable solid phase. For siderite, the coupling involves the release of Fe2+ ions that subsequently become oxidized and then precipitate in the form of FeIII oxyhydroxides. For dolomite and magnesite, dissolution in the presence of pure water (undersaturated with any possible phase) results in the immediate precipitation of hydrated Mg-carbonate phases. In all these systems, dissolution and precipitation are coupled and occur directly in a boundary layer at the carbonate surface. Scaling arguments demonstrate that the thickness of this boundary layer is controlled by the rate of carbonate dissolution, the equilibrium concentration of the precipitates and the kinetics of diffusion of species in a boundary layer. From these parameters a characteristic time scale and a characteristic length scale of the boundary layer can be derived. This boundary layer grows with time and never reaches a steady state thickness as long as dissolution of the carbonate is faster than precipitation of the new mineral. At ambient temperature, the surface reactions of these dissolving carbonates occur on time-scales of the order of seconds to minutes, indicating the rapid surface rearrangement of carbonates in the presence of aqueous fluids. As a consequence, many carbonate-fluid reactions in low temperature environments are controlled by local thermodynamic equilibria rather than by the global equilibrium in the whole system. 相似文献
70.
Anja Bretzler Lucien Stolze Julien Nikiema Franck Lalanne Elaheh Ghadiri Matthias S.Brennwald Massimo Rolle Mario Schirmer 《地学前缘(英文版)》2019,10(5):1685-1699
The semi-arid Sahel regions of West Africa rely heavily on groundwater from shallow to moderately deep(100 m b.g.l.)crystalline bedrock aquifers for drinking water production.Groundwater quality may be affected by high geogenic arsenic(As)concentrations(10μg/L)stemming from the oxidation of sulphide minerals(pyrite,arsenopyrite)in mineralised zones.These aquifers are still little investigated,especially concerning groundwater residence times and the influence of the annual monsoon season on groundwater chemistry.To gain insights on the temporal aspects of As contamination,we have used isotope tracers(noble gases,~3H,stable water isotopes(~2 H,~(18)O))and performed hydrochemical analyses on groundwater abstracted from tube wells and dug wells in a small study area in southwestern Burkina Faso.Results revealed a great variability in groundwater properties(e.g.redox conditions,As concentrations,water level,residence time)over spatial scales of only a few hundred metres,characteristic of the highly heterogeneous fractured underground.Elevated As levels are found in oxic groundwater of circum-neutral pH and show little relation with any of the measured parameters.Arsenic concentrations are relatively stable over the course of the year,with little effect seen by the monsoon.Groundwater residence time does not seem to have an influence on As concentrations,as elevated As can be found both in groundwater with short(50 a)and long(10~3 a)residence times as indicated by ~3He/~4He ratios spanning three orders of magnitude.These results support the hypothesis that the proximity to mineralised zones is the most crucial factor controlling As concentrations in the observed redox/pH conditions.The existence of very old water portions with residence times10~3 years already at depths of50 m b.g.l.is a new finding for the shallow fractured bedrock aquifers of Burkina Faso,suggesting that overexploitation of these relatively low-yielding aquifers may be an issue in the future. 相似文献