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221.
The first post‐injection seismic monitor survey at the Ketzin pilot CO2 storage site: results from time‐lapse analysis
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Fei Huang Peter Bergmann Christopher Juhlin Monika Ivandic Stefan Lüth Alexandra Ivanova Thomas Kempka Jan Henninges Daniel Sopher Fengjiao Zhang 《Geophysical Prospecting》2018,66(1):62-84
The injection of CO2 at the Ketzin pilot CO2 storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO2 was injected into a saline aquifer. A third repeat three‐dimensional seismic survey, serving as the first post‐injection survey, was acquired in 2015, aiming to investigate the recent movement of the injected CO2. Consistent with the previous two time‐lapse surveys, a predominantly west–northwest migration of the gaseous CO2 plume in the up‐dip direction within the reservoir is inferred in this first post‐injection survey. No systematic anomalies are detected through the reservoir overburden. The extent of the CO2 plume west of the injection site is almost identical to that found in the 2012 second repeat survey (after injection of 61 kt); however, there is a significant decrease in its size east of the injection site. Assessment of the CO2 plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO2 dissolution, and CO2 migration into thin layers, in addition to the effects of ambient noise. Four‐dimensional seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO2 after the second repeat survey and the CO2 migrating into thin layers and being dissolved was reached by the time of the first post‐injection survey. In view of the significant uncertainties in CO2 mass estimation, both patchy and non‐patchy saturation models for the Ketzin site were taken into consideration. 相似文献
222.
Alexandra Gross Jeremy Kiszka Olivier Van Canneyt Pierre Richard Vincent Ridoux 《Estuarine, Coastal and Shelf Science》2009,84(3):367
Mayotte in the southwest Indian Ocean is characterized by high dolphin diversity. They may coexist within a fairly small area around the island because they exploit neither the same preferential habitats nor the same resources. This preliminary study aimed to investigate ecological niche segregation among these delphinid communities: the Indo-Pacific bottlenose dolphin, Tursiops aduncus, the pantropical spotted dolphin, Stenella attenuata, the spinner dolphin, Stenella longirostris, and the melon-headed whale, Peponocephala electra. Two approaches were used. Habitat preferences were investigated by analysing dolphin sighting data and associated physiographical characteristics. Resource partitioning was explored by analysing C and N stable isotopes in skin and blubber biopsies. Only T. aduncus, which showed clear association with coastal habitats in the lagoon, differed from the others in terms of habitat preferences, characterised by shallow depth and slope, and proximity to the coast. All other species shared similar oceanic habitats immediately outside the lagoon, these being of higher depth and slope, greater distance from the coast and were not discernable by discriminant analysis. The two Stenella species and the melon-headed whale displayed very high overlap in habitat physiographic variables. The analysis of stable isotopes confirmed the ecological isolation of T. aduncus and revealed a clear segregation of P. electra compared to the two Stenella that was not apparent in the habitat analysis. This may reflect ecological differences that were not observable from diurnal surface observations. 相似文献
223.
Aymeric Dabrin Jrg Schfer Grard Blanc Emilie Strady Matthieu Masson Ccile Bossy Sabine Castelle Naïg Girardot Alexandra Coynel 《Estuarine, Coastal and Shelf Science》2009,84(4):429-439
Dissolved Cd (CdD) concentrations along the salinity gradient were measured in surface water of the Gironde Estuary during 15 cruises (2001–2007), covering a wide range of contrasting situations in terms of hydrology, turbidity and season. During all situations dissolved Cd concentrations displayed maximum values in the mid-salinity range, reflecting Cd addition by chloride-induced desorption and complexation. The daily net CdD fluxes from the Gironde Estuary to the coastal ocean were estimated using Boyle's method. Extrapolating CdD concentrations in the high salinity range to the freshwater end member using a theoretical dilution line produced 15 theoretical Cd concentrations (CdD0), each representative of one distinct situation. The obtained CdD0 concentrations were relatively similar (201 ± 28 ng L−1) when freshwater discharge Q was >500 m3 s−1 (508 ≤ Q ≤ 2600 m3 s−1), but were highly variable (340 ± 80 ng L−1; 247–490 ng L−1) for low discharge situations (169 ≤ Q ≤ 368 m3 s−1). The respective daily CdD net fluxes were 5–39 kg day−1, mainly depending on freshwater discharge. As this observation invalidates the existing method of estimating annual CdD net fluxes, we proposed an empirical model, using representative CdD0 values and daily freshwater discharges for the 2001–2007 period. Subsequent integration produced reliable CdD net flux estimates for the Gironde Estuary at the annual timescale that ranged between 3.8–5.0 t a−1 in 2005 and 6.0–7.2 t a−1 in 2004, depending on freshwater discharge. Comparing CdD net fluxes with the incoming CdD fluxes suggested that the annual net CdD addition in the Gironde Estuary ranged from 3.5 to 6.7 t a−1, without any clear temporal trend during the past seven years. The annual CdD net fluxes did not show a clearly decreasing trend in spite of an overall decrease by a factor 6 in Cd gross fluxes during the past decade. Furthermore, in six years out of seven (except 2003), the annual CdD net fluxes even exceeded river borne total (dissolved + particulate) gross Cd fluxes into the estuary. These observations were attributed to progressive Cd desorption from both suspended particles and bottom sediment during various sedimentation–resuspension cycles induced by tidal currents and/or continuous dredging (navigation channel) and diverse intra-estuarine sources (wet deposition, urban sources, and agriculture). Provided that gross fluxes remain stable over time, dissolved Cd exportation from the Gironde Estuary to the coastal ocean may remain at the present level for the coming decade and the estuarine sedimentary Cd stock is forecast to decrease slowly. 相似文献
224.
Emilie Strady Grard Blanc Jrg Schfer Alexandra Coynel Aymeric Dabrin 《Estuarine, Coastal and Shelf Science》2009,83(4):550-560
Understanding trace metal behaviour in estuarine environments requires sampling strategies and analytical methods adapted to strong physical and geochemical gradients. In this study, we present a specific sampling strategy covering a wide range of hydrological conditions during nine cruises in 2003–2007 to characterise the behaviour of three dissolved metals (uranium, vanadium and molybdenum) in surface and bottom water along the salinity gradient of the highly turbid macrotidal Gironde Estuary using a solid–liquid extraction. Uranium behaved conservatively whatever the water discharges observed. The slight dissolved U depletion compared to the theoretical dilution line between the fluvial and marine end-members occasionally observed in the low salinity range (0–3) was attributed to the mixing of different water bodies of the Gironde tributaries. In contrast, dissolved V behaviour was largely influenced by the hydrological conditions, showing increasingly pronounced addition with decreasing freshwater discharges, (i.e. increasing residence times of water and particles in the estuary). This addition of dissolved V in the low- to mid-salinity range was attributed to desorption processes observed in the Maximum Turbidity Zone (MTZ). The distribution of dissolved Mo concentrations along the salinity gradient was highly variable. Apparent conservative, and non-conservative behaviours were observed and were related to the concomitance of desorption from SPM, inputs from sediments for additive distribution and biological uptake and removal into sediments for subtractive distribution. Based on the whole database (2003–2007), annual net fluxes to the coastal ocean were estimated for dissolved U (15.5–16.6 t yr−1) and V (31.3–36.7 t yr−1). 相似文献
225.
Tomáš Bešta Jan Novák Dagmar Dreslerová Vlasta Jankovská Alexandra Bernardová Lenka Lisá Daniela Valentová 《Boreas: An International Journal of Quaternary Research》2015,44(3):563-574
Palaeolimnological reconstruction of the aquatic environment in Lake Komo?any, based on sedimentology, geochemistry, and diatom and macrofossil analyses in the littoral part of the basin, reflects the mid‐Holocene history of the profile from its origin c. 9100 cal. a BP to its final transformation into an alder carr c. 4100 cal. a BP. The existence of the littoral zone can be best explained by increased precipitation during the studied interval. A stable diatom community, diatom‐inferred total phosphorus (50–80 μg L?1) and pH (~7.6), along with stable concentrations of elements associated with changes in its watershed indicate a long‐lasting, balanced aquatic environment with no major shifts attributable to external factors, including climate change. From c. 4700 cal. BP, there started a transition to terrestrial conditions, caused by either natural infilling processes or decreased precipitation. Alternation of remarkable dry/wet phases was not detected, in contrast to numerous analogous central European and supraregional records. Potential human impact was revealed through increases of Corylus and Populus pollen in the Neolithic. These anthropogenic changes in the lake surroundings had no detectable influence on the lacustrine environment. The gathered data suggest undramatic, balanced mid‐Holocene environmental and climatic settings for this central European locality, in direct contrast to numerous analogous studies from the region emphasizing fluctuations and shifts found in the sediment record. 相似文献
226.
227.
Sally Thompson Gabriel Katul Alexandra KoningsLuca Ridolfi 《Advances in water resources》2011,34(8):1049-1058
Lateral redistribution of surface water in patchy arid ecosystems has been hypothesized to contribute to the maintenance of vegetation patches through the provision of a water subsidy from bare sites to vegetated sites. Such runon-runoff processes occur during Hortonian runoff events on topographically sloping ground. Surface flow redistribution may also occur on topographically flat ground if the presence of the vegetation patch creates a contrast in infiltration rate, leading to a free-surface gradient in ponded water. The precise dynamics and the eco-hydrologic role of this process has resisted complete theoretical treatment to date. Here the overland flow equations are modified to account for the presence of vegetation situated over a flat surface. The resulting model is solved numerically to determine whether this mechanism could influence the spatial partitioning of water in patchy arid ecosystems. Assumptions made about infiltration processes and overland flow in existing eco-hydrologic models of patchy and patterned arid ecosystems are evaluated in comparison to the solution of the ‘full’ coupled Saint-Venant equations with various infiltration models. The results indicate that the optimization of vegetation spatial patch scales with respect to water redistribution may be determined by the size of the infiltration redistribution length L over which the presence of an infiltration contrast perturbs baseline infiltration behavior. 相似文献
228.
Marta Rodrigues Anabela Oliveira Martha Guerreiro André Bustorff Fortunato José Menaia Luís Mesquita David Alexandra Cravo 《Ocean Dynamics》2011,61(6):841-856
This study aims at understanding the fecal contamination behavior in a small coastal stream (Aljezur, Portugal), which has
significant economic and ecological values. Like in most small coastal systems, circulation and water renewal in the Aljezur
stream exhibit a strong variability due to their dependence on tides, waves, intermittent river flows, and a highly variable
morphology. Hence, the problem was approached through a combination of field surveys and the development and application of
a hard-coupled three-dimensional hydrodynamic and fecal contamination model. Salinity and temperature results have shown that
mixing and transport in the stream are very sensitive to the river flow and wind forcing. The model is able to represent the
main patterns and trends observed in Escherichia coli and fecal enterococcus concentrations along the stream, for different environmental and contamination conditions, suggesting
die-off rates on the order of 0.50–0.55 day−1. Die-off rate and the representation of the sediment-associated processes were identified as the major remaining sources
of uncertainty in the model. Results show that, owing to the processes that occur along the stream, fecal bacteria reach the
beaches water in numbers that comply with the European Bathing Waters Directive, even during the summer periods when the upstream
concentrations are larger. In particular, results suggest a direct relation between the tidal propagation upstream and the
reduction of the fecal bacteria concentrations along the stream that can be relevant for the development of a strategy for
the management of the system’s water safety. 相似文献
229.
230.
Evaluating the anthropogenic impacts on groundwaters; a methodology based on the determination of natural background levels and threshold values 总被引:1,自引:0,他引:1
Alexandra Gemitzi 《Environmental Earth Sciences》2012,67(8):2223-2237
The present work investigates the long-term effects of human intervention on groundwaters based on the determination of natural background levels (NBLs) and threshold values (TVs) for groundwater electrical conductivity, chloride, ammonium, sulphates and nitrates. The methodology adopted is the one proposed in the 6th Framework European Project ??BRIDGE??, which was applied with some adjustments in Rhodope area (Northern Greece). The study area was especially selected because it incorporates two distinct subareas: the northern one which can be safely considered as a pristine area, where NBLs for groundwaters were assessed from; the southern part which forms a typical Mediterranean region, intensively cultivated for the last 40?years. Groundwater TVs were determined considering two types of groundwater receptors: (a) groundwater ??itself?? and (b) groundwater dependent lagoons in the coastal part of the study area. Results showed that groundwater quality is altered seriously from its natural background composition indicating how human activities have affected groundwater quality and showed that chemical status of groundwater has been seriously aggravated. The number and the spatial distribution of monitoring locations exceeding TVs revealed that chloride and nitrates are the most serious threats for groundwater in the study area. 相似文献