Flow in the unsaturated zone around a shallow subsurface radioactive waste trench: Interpretation of an infiltration–drainage test at the Chernobyl Pilot Site     

N. Van Meir  J.P. Gaudet  V. Phrommavanh  J.P. Laurent  D. Bugai  R. Biron 《Applied Geochemistry》2012

This article describes an infiltration–drainage test carried out in the unsaturated zone (UZ) at the Chernobyl Pilot Site during October 2008; this is an international radioecology study site and is the subject of several papers in this special issue. The test has to be seen in the larger context of radionuclide transport from a waste trench. The conducted experiment consisted of infiltrating a layer of 9.5 cm of water in a circular area of 5.51 m² over 5 h. Its main objective was to create a larger range of water content values (and hence suction pressure values), not only at the top of the soil profile but also at greater depths, in this case up to 1.50 m. Observations of water content and suction pressure were carried out continuously at seven different depths during infiltration, drainage and during the return to natural conditions over a period of several months. This allowed deriving UZ parameter values with greater confidence than those derived from monitoring small natural water content changes over periods of years.  相似文献   

Limitations in the use of compound-specific stable isotope analysis to understand the behaviour of a complex BTEX groundwater contamination near Brussels (Belgium)     

Ilse Van Keer  Jan Bronders  Jeroen Verhack  Jan Schwarzbauer  Rudy Swennen 《Environmental Earth Sciences》2012,66(2):457-470

The application of compound-specific stable isotope analysis (CSIA) was evaluated to characterise a complex groundwater contamination. For this purpose, δ¹³C and δ²H analysis of benzenes and alkylated derivatives were used to interpret both the impact of different sources on a contaminant plume and the presence of degradation processes. The different contaminant sources could be distinguished based on their combined δ¹³C–δ²H signature of the benzene, toluene, ethylbenzene and xylenes (BTEX) dissolved in the groundwater. Despite this source differentiation, plume characterisation was not possible due to the complex mixing of the respective contaminant plumes. Furthermore, the original isotope signatures of the sources were not preserved across these plumes. To estimate the level of in situ biodegradation independently from concentration data, the Rayleigh equation was used. Although current literature identifies the application of CSIA as very promising in the frame of characterising organic groundwater pollution, this study has indicated that this approach can be limited with respect to successfully distinguish the different plumes and their relation to the known source zones.  相似文献   

Thermal Impact on Damaged Boom Clay and Opalinus Clay: Permeameter and Isostatic Tests with μCT Scanning     

G. J. Chen  T. Maes  F. Vandervoort  X. Sillen  P. Van Marcke  M. Honty  M. Dierick  P. Vanderniepen 《Rock Mechanics and Rock Engineering》2014,47(1):87-99

Within the framework of the TIMODAZ project, permeameter tests and isostatic tests were performed on Boom Clay and Opalinus Clay in order to assess the impact of temperature, pore water composition, and confining stress on the sealing of damaged samples of Boom Clay and Opalinus Clay. A microfocus X-ray computed tomography technique was used to visualize the evolution of the sealing process. Compared to the fast sealing of Boom Clay, the sealing of Opalinus Clay was much slower. The heating showed a significant, favorable impact on the sealing behavior of Opalinus Clay under permeameter test conditions, while the sealing behavior of Boom Clay appeared to be unaffected. Tests performed under isostatic conditions did not reveal a significant influence of a heating–cooling cycle on the sealing behavior of these clays. The reappearance of the fractures or holes in the samples after dismantling confirms earlier observations which showed that after sealing, the original mechanical properties are not recovered. In other words, a heating cycle does not seem to induce healing.  相似文献   

Utilization of palm oil mill effluent for polyhydroxyalkanoate production and nutrient removal using statistical design     

M. F. Md. Din  M. Ponraj  M. Van Loosdrecht  Z. Ujang  S. Chelliapan  V. Zambare 《International Journal of Environmental Science and Technology》2014,11(3):671-684

The optimization for poly-β-hydroxyalkanoate production was carried out with nutrient removal efficiency for total organic carbon (TOC), phosphate, and nitrate from palm oil mill effluent waste. The experiment was conducted in a fabricated fed-batch reactor and the data obtained was analyzed using central composite rotatable design and factorial design for response surface methodology as a systematic approach for designing the experiment statistically to obtain valid results with minimum effort, time, and resources. The analysis of numerical optimization with propagation of error showed that 66 % of poly-β-hydroxyalkanoate production can be obtained with nutrient removal of TOC and nitrate by 19 and 3 %, respectively. However, phosphate removal efficiency was not found to be much effective. More over, the chemical oxygen demand: nitrogen phosphate (509 g/g N), chemical oxygen demand: phosphate (200 g/g P), air flow rate (0.59 L/min), substrate feeding rate (20 mL/min), and cycle length (20 h) were the optimized variables for maximum poly-β-hydroxyalkanoate production and nutrient removal.  相似文献   

Characterisation of rapid infiltration flows and vulnerability in a karst aquifer using a decomposed fluorescence signal of dissolved organic matter     

Marine Quiers  Christelle Batiot-Guilhe  Cristina C. Bicalho  Yves Perrette  Jean-Luc Seidel  Sandra Van Exter 《Environmental Earth Sciences》2014,71(2):553-561

The fluorescent properties of dissolved organic matter (DOM) have been used as natural tracers in various water systems. However, only few studies have focused on groundwater systems, specifically, on karst systems. The aim of this study was to develop the use of the DOM fluorescence signal as a natural tracer, considering the multiple compartments of a karst system. This method was applied to the Lez hydrosystem, which supplies the city of Montpellier with drinking water. The hydrodynamics and hydrochemistry of the spring were monitored beginning March 2006. The DOM fluorescence was measured by the excitation–emission matrix spectroscopy technique. The analysis of the total fluorescence signal confirms the efficiency of this tool to trace rapid infiltration flows. Moreover, the decomposition of the signal into different fluorophores complements the information provided by the total signal. Indeed, the fluorescence emitted by the humic compounds seems to be the ideal tool for identifying rapid infiltration flows. Nevertheless, the fluorescence of protein-like compounds is better correlated with the inflow of faecal bacteria at the outlet. This decomposition of the fluorescence signal is an interesting way to provide information on both the rapid infiltration flow as well as the vulnerability of the karst aquifers.  相似文献   

Physical and chemical steady-state compaction in deep-sea sediments: Role of mineral reactions     

Parisa Jourabchi  Ivan L’Heureux  Philippe Van Cappellen 《Geochimica et cosmochimica acta》2010,74(12):3494-3513

Marine sediments typically exhibit steep porosity gradients in their uppermost centimeters. Although the decrease in porosity with depth below the sediment-water interface is primarily due to compression arising from the accumulation of overlying sediment, early diagenetic mineral dissolution and precipitation reactions may potentially also affect the porosity gradient. Here, we present a steady state compaction model, based on the mass and momentum conservation of total fluid and solid phases, in order to quantify the relative contributions of mineral reactions and physical compaction on porosity changes. The compaction model is applied to estimate hydraulic conductivity and compressive response coefficients of deep-sea sediments from measured porosity depth profiles. The results suggest an inverse relation between the compressive response coefficient and the lithogenic content of marine sediments. For deep-sea sediments exhibiting high rates of dissolution of siliceous shell fragments, the compaction model ignoring mineral reactions overestimates the hydraulic conductivity and compressive response coefficients. In contrast to non-compacting porous media, mineral dissolution in surficial sediments can lead to lower porosity. However, as illustrated for a deep-sea sediment in the equatorial Atlantic characterized by extensive dissolution of calcareous shell fragments, the effect of mineral dissolution and precipitation reactions on porosity gradients is, in most cases, negligible.  相似文献   

Collapsing volcanoes: the sleeping giants' threat     

Thomas Shea  Benjamin Van Wyk de Vries 《Geology Today》2010,26(2):72-77

Dormant volcanoes are typically thought of as relatively safe environments to live around. However, under certain geological conditions, such volcanoes can be prone to collapse and may generate massive rockslide avalanches reaching tens of kilometres from the volcano.  相似文献   

Sensitivity of two psychrophilic diatoms to crude oil and fuel oil     

Chase Van Baalen  Rita O&#x;Donnell 《Marine environmental research》1984,12(1):63-68

Two pure cultures of diatoms, a Nitzschia sp. and a Chaetoceros sp., were grown at 0°C or 10°C in the presence of two crude oils and two fuel oils. The petroleum samples were absorbed onto filter paper discs and added directly to the algal cultures. In all cases the organisms were much more sensitive to the crude oils or fuel oils when growing at 0°C than at 10°C. The rate of photosynthesis measured by an oxygen electrode for Nitzschia sp. grown and tested at 0°C was not affected during 3 hours' incubation with some four times the amount of a crude oil or fuel oil that blocked growth. The experiments lead to the cautious suggestion that psychrophilic algae will prove some fivefold more sensitive than mesophilic algae to petroleum pollution.  相似文献   

Containment of groundwater pollution (methyl tertiary butyl ether and benzene) to protect a drinking-water production site in Belgium     

Pieter Jan Haest  Richard Lookman  Ilse Van Keer  Johan Patyn  Jan Bronders  Marjan Joris  Jan Bellon  Florimond De Smedt 《Hydrogeology Journal》2010,18(8):1917-1925

The subsurface migration of methyl tertiary butyl ether (MTBE) and benzene towards a drinking-water production site in Belgium was monitored for 9 years. A large gasoline spill at a nearby fuel station had caused a 500-m long and 50-m-wide pollution plume of MTBE (10?30 mg/L) and benzene (2?10 mg/L). In order to prevent any intrusion of pollutants into the drinking-water supply, a conceptual model was used to design a pump-and-treat system that intercepted the gasoline-contaminated groundwater emanating from the spill. The contaminated soil in the spill zone was excavated. A numerical mass transport model was developed to evaluate the ongoing plume containment. The model describes the subsurface MTBE migration and was regularly updated, based on groundwater monitoring data and the measured mass of MTBE extracted with the pump-and-treat system. With continued interception pumping, the MTBE plume can be remediated in 14 years. Without it, MTBE and benzene concentrations up to 600 μg/L could have reached the drinking-water production site and the plume would persist for 9 years longer. Source zone treatment combined with plume interception pumping is a suitable risk-based remediation strategy for the containment of MTBE and benzene groundwater pollution.  相似文献   

The nature of MIS 3 stadial–interstadial transitions in Europe: New insights from model–data comparisons     

C.J. Van Meerbeeck  H. Renssen  D.M. Roche  B. Wohlfarth  S.J.P. Bohncke  J.A.A. Bos  S. Engels  K.F. Helmens  M.F. Sánchez-Goñi  A. Svensson  J. Vandenberghe 《Quaternary Science Reviews》2011,30(25-26):3618-3637

15 abrupt warming transitions perturbed glacial climate in Greenland during Marine Isotope Stage 3 (MIS 3, 60–27 ka BP). One hypothesis states that the 8–16 °C warming between Greenland Stadials (GS) and Interstadials (GI) was caused by enhanced heat transport to the North Atlantic region after a resumption of the Atlantic Meridional Overturning Circulation (AMOC) from a weak or shutdown stadial mode. This hypothesis also predicts warming over Europe, a prediction poorly constrained by data due to the paucity of well-dated quantitative temperature records. We therefore use a new evidence from biotic proxies and a climate model simulation to study the characteristics of a GS–GI transition in continental Europe and the link to enhanced AMOC strength. We compare reconstructed climatic and vegetation changes between a stadial and subsequent interstadial – correlated to GS15 and GI14 (～55 ka BP) – with a simulated AMOC resumption using a three-dimensional earth system model setup with early-MIS 3 boundary conditions. Over western Europe (12°W–15°E), we simulate twice the annual precipitation, a 17 °C warmer coldest month, a 8 °C warmer warmest month, 1300 °C-day more growing degree days with baseline 5 °C (GDD5) and potential vegetation allowing tree cover after the transition. However, the combined effect of frequent killing frosts, <20 mm summer precipitation and too few GDD5 after the transition suggest a northern tree limit lying at ～50°N during GI14. With these 3 climatic limiting factors we provide a possible explanation for the absence of forests north of 48°N during MIS 3 interstadials with mild summers. Finally, apart from a large model bias in warmest month surface air temperatures, our simulation is in reasonable agreement with reconstructed climatic and vegetation changes in Europe, thus further supporting the hypothesis.  相似文献