The origin of high sulfate concentrations and hydrochemistry of the Upper Miocene–Pliocene–Quaternary aquifer complex of Jifarah Plain,NW Libya     

Nawal Alfarrah  Gebremedhin Berhane  Ibrahimu Chikira Mjemah  Marc Van Camp  Kristine Walraevens 《Environmental Earth Sciences》2016,75(20):1388

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Using stable water isotopes to identify spatio-temporal controls on groundwater recharge in two contrasting East African aquifer systems     

Samson Oiro  Jean-Christophe Comte  Chris Soulsby  Kristine Walraevens 《水文科学杂志》2018,63(6):862-877

Understanding the spatio-temporal variability in groundwater recharge is a prerequisite to sustainable management of aquifers. Spatial analysis of groundwater stable isotopes uncovered predominant controls on groundwater recharge in the Nairobi aquifer system (NAS) and the South Coast aquifer (SC), two exemplar East African aquifers relied upon by 7 million people. We analysed 368 samples for stable isotopes and basic physico-chemical parameters. The NAS groundwater isotopes are controlled by precipitation orographic effects and enriched recharge from impounded lakes/wetlands; the SC isotopes are correlated with water-table depth influencing evapotranspiration. Global Network of Isotopes in Precipitation (GNIP) data revealed groundwater recharge during months of heavy rains in the NAS, whilst the SC experiences spatio-temporally diffuse recharge. Inferred “isoscapes” show: in the NAS, (1) direct, rapid recharge favoured by faults, well-drained soils and ample rainfall in uplands, (2) delayed recharge from impounded lakes and wetlands in mid-lands, and (3) focused, event-based recharge in floodplains; and in the SC, diffuse recharge complicated by significant water-table evapotranspiration processes.  相似文献   

Traits of Volunteer Water Monitoring Programs that Influence Natural Resource Management and Policy Impacts     

Kristine F. Stepenuck  Kenneth D. Genskow 《社会与自然资源》2019,32(3):275-291

As citizens take on expanded roles in gathering and reporting environmental data, their potential impact may relate to organizational traits. This study sought to understand the relationship through a survey that identified traits and impacts of U.S. volunteer water monitoring programs on natural resource policy and management. A multiple regression model tested the influence of nine traits on an index of impact, addressing eight a priori hypotheses related to natural resource management outcomes. Seven traits were significantly related to impacts. Significant positive relationships included: the objective to address an environmental crisis; an EPA and/or state-approved quality assurance plan; support of external decision makers who may use or benefit from data; larger budget; volunteers playing more roles in the research process. Fewer impacts were expected from programs operating within schools. Understanding these relationships can help guide citizen science programs or other types of citizen engagement efforts.  相似文献   

Effects of multi-annual climate variability on the hydrodynamic evolution (1833 to present) in a shallow aquifer system in northern Belgium     

Marc Van Camp  Marleen Coetsiers  Kristine Martens  Kristine Walraevens 《水文科学杂志》2013,58(5):763-779

Abstract

Using a groundwater flow model and long historical meteorological time series data, the evolution of the groundwater flow regime in a multi-layered groundwater flow basin in northern Belgium during the last one and a half centuries (since 1833) is reconstructed. Model output parameters such as piezometric levels, depth to water table, seepage fluxes in the valleys and calculated baseflow to the river system are presented and inter-annual and decadal variations are evaluated against seasonal fluctuations. The main time-varying boundary condition in the model is the aquifer recharge which was estimated using the method of Thornthwaite and Mather based on precipitation and temperature data. The model does not take into account changes in boundary conditions due to changes in land use (deforestation, drainage of cultivated land) or groundwater exploitation. Variations in model output parameters are therefore only due to climatological forcing. Only the natural non-exploited state of the aquifer is considered. Although few historical piezometric measurements are available to verify model output, the results give an indication of the natural hydrodynamic variations on a time scale of decades.

Citation Van Camp, M., Coetsiers, M., Martens, K. & Walraevens, K. (2010) Effects of multi-annual climate variability on the hydrodynamic evolution (1833 to present) in a shallow aquifer system in northern Belgium. Hydrol. Sci. J. 55(5), 763–779.  相似文献   

Geological and geotechnical constraints for urban planning and natural environment protection: a case study from Mekelle City, Northern Ethiopia     

Gebremedhin Berhane  Kristine Walraevens 《Environmental Earth Sciences》2013,69(3):783-798

The study was conducted in the rapidly expanding city of Mekelle located in the northern part of Ethiopia, East Africa. An integrated approach including geomorphological, geological and engineering geological, geotechnical and hydrogeological methods were used to characterize the natural urban environment to be used as a baseline for protection and rational planning of development. Conventional field observation, test pits and drilled boreholes were used to collect soil, rock and water samples and standard laboratory procedures were applied. The results revealed that the main geologic constraints to sustainable development of the city are active erosion, instability of slopes, flood hazard, cyclic/alternating hard and weak rock layers, high swelling–shrinkage soils, shallow and unconfined groundwater with variable composition and high susceptibility to corrosion and pollution. It is recommended to avoid development and expansion of the city in areas of steep land forms, at the foot of steep slopes and in areas covered by black alluvial soil deposits. Development of a systematic multidisciplinary database aided by GIS, with continuous monitoring and updating is also highly recommended and will be useful for further refined geotechnical microzonation. It is the authors’ belief that this study highlights the basic constraints and hazards the city is facing, and provides baseline information and awareness to the city planners, decision makers, geo-environmentalists, engineers and the community for future expansion and rehabilitation plans and to tackle the existing hazards.  相似文献   

Consequences of Water Level Drops for Soft Sediment Deformation and Vertical Fluid Leakage     

Christian Hermanrud  Jon Marius Venstad  Joe Cartwright  Lars Rennan  Kristine Hermanrud  Hege M. Nordgård Bolås 《Mathematical Geosciences》2013,45(1):1-30

Both water level drops and erosion have previously been suggested as causes of fluid overpressures in the subsurface. Quantification of the relevance of these processes to supra-lithostatic fluid pressure formation with a wide selection of input parameters is lacking, and thus desired. The magnitudes and drop times that are required for water level drops to result in supra-lithostatic pore pressures in a variety of situations are calculated. Situations with pore fluids consisting of water, water with dissolved methane, water with a gas hydrate layer and dissolved methane in the underlying sediments, and water with dissolved methane, a gas hydrate layer, and free gas accumulation below the hydrate layer are separately addressed. The overpressure formation from reservoir gas expansion is also simulated. The simulation results demonstrate that high fluid overpressures can develop in a rock as a response to a water level drop without the presence of gas, provided that the rock has a sufficiently low compressibility. The contribution to fluid overpressuring is however dramatically increased if the pore water is saturated with methane prior to the water level drop, and is further amplified by the presence of gas hydrates and free gas accumulations beneath such hydrates. Gas expansion in reservoirs should be expected to significantly increase the fluid overpressures in shallow, sealed pressure compartments that experience erosion or water level drops, even if the water level drop duration exceeds one million years. Enough relationships between the calculated overpressure formation and the main controlling factors are provided in order to enable readers to make inferences about a variety of geological settings. Analyses of simulation results prompt us to suggest that pockmarks are likely to be triggered by gas expansion in vertical fluid migration pathways, that the giant craters at the seabed west of Albatross South in the Barents Sea result from hydrate dissociation, and that overpressure build-up due to gas expansion has contributed to reservoir overpressuring in many eroded basins, including the Hammerfest Basin in the Barents Sea.  相似文献   

Condemning the public: Design and New York's new 42nd Street     

Kristine Miller 《GeoJournal》2002,58(2-3):139-148

This paper examines the redevelopment of Times Square in New York City and brings together two discourses, the discourse of design and the discourse of eminent domain case law. I argue that both were inextricable parts of the Times Square redevelopment process and served similar functions: defining a public for The New Times Square. By determining what was `in the public interest', eminent domain case law set out two opposing publics: the criminal Times Square public and an idealized general public. By selectively editing the Times Square public's desires and behaviors, design helped define and represent new moral norms.  相似文献   

A new correction model for C ages in aquifers with complex geochemistry – Application to the Neogene Aquifer,Belgium     

Marleen Coetsiers  Kristine Walraevens 《Applied Geochemistry》2009

The objective of this paper is to build a general correction model that takes into account all the different radiocarbon-dilution reactions and resolving the processes that are geochemically “aging” the groundwater in the Neogene Aquifer. For this, δ¹³C and radiocarbon in groundwater are investigated with their relationship to other chemical components in groundwater. The δ¹³C values in the Neogene Aquifer are influenced by various geochemical reactions like calcite dissolution, oxidation of organic matter and methanogenesis. Calcite dissolution and CH₄ production increase δ¹³C while the oxidation of organic matter decreases δ¹³C in the groundwater. The reactions that modify δ¹³C also influence the ¹⁴C activity. Due to the complex geochemical environment, existing correction models are not applicable to this situation. A correction model for initial ¹⁴C activity is formulated in which the different C sources that influence ¹⁴C activity are taken into account. It is observed that recent dissolved organic matter plays an important role in redox reactions. The corrected ¹⁴C ages lie between −0.792 and 6.425 ka representing the maximum age. If a part of the organic matter that oxidises is fossil, the determined age will represent an overestimated age.  相似文献   

Late glacial palaeoceanography of Hinlopen Strait, northern Svalbard   总被引：3，自引：0，他引：3  

Nalân Koç  Dorthe Klitgaard-Kristensen  Kristine Hasle  Carl Fredrik Forsberg  ers Solheim 《Polar research》2002,21(2):307-314

Timing and structure of the Late and post-glacial development of the northern Svalbard margin, together with the initial influx of Atlantic water into the Arctic Ocean are still very poorly constrained. We investigated a sediment core (NP94-51) from a high accumulation area on the continental shelf north of Hinlopen Strait with the purpose of resolving the timing and structure of the last deglaciation. Detailed analyses of ice-rafted detritus, benthic and planktonic foraminiferal fauna, diatom flora, grain size and radiocarbon dates are used to reconstruct the palaeoceanographic evolution of the area. Our results indicate that the disintegration of Hinlopen Strait ice and possibly the northern margin of the Svalbard Ice Sheet commenced between 13.7 and 13.9 ¹⁴C Ky BP. Influx of subsurface Atlantic waters into the area (12.6 ¹⁴C Ky BP) and the retreat of the sea ice cover, with the accompanying opening of the surface waters (10.8 ¹⁴C Ky BP), happened at different times and both much later than the disintegration of the ice sheets. The transition into the Holocene shows a two-step warming.  相似文献   

High Precision Ru, Pd, Ir, Pt, Re and REE Determinations in the Stevns Klint Cretaceous-Tertiary Boundary Reference Material (FC-1) by Isotope Dilution Multiple Collector Inductively Coupled Plasma-Mass Spectrometry   总被引：1，自引：0，他引：1  

Kristine Krogh Jensen  Joel Baker  Tod Waight  Robert Frei  David W. Peate 《Geostandards and Geoanalytical Research》2003,27(1):59-66

We present high precision Ir, Ru, Pt, Pd, Re and rare earth element (REE) determinations by isotope dilution multiple collector-ICP-MS on the Cretaceous-Tertiary boundary sedimentary reference material FC-1. Samples for platinum-group element measurements were digested in Carius tubes followed by acid digestion. The platinum-group elements were subsequently separated by anion exchange chemistry and determined by multiple collector-ICP-MS. The accuracy of the platinum-group element analyses have been verified by comparative analyses of the reference materials WITS-1 and GP13 (sample size 0.5-1 g). Replicate analyses of FC-1 (sample size 0.2 g) exhibit good reproducibility (RSD < 5%) for all the analysed platinum-group elements. REE data also exhibit excellent reproducibility (RSD < 0.5%), which indicates that this sample is homogeneous for the determination of the platinum-group elements and REE at the 0.2 g level.  相似文献