A review of analogues of alkaline alteration with regard to long-term barrier performance

2011 ◽  
Vol 75 (4) ◽  
pp. 2401-2418 ◽  
Author(s):  
D. Savage
Keyword(s):  
Mineral Dissolution ◽  
Time Intervals ◽  
Barrier Materials ◽  
Disturbed Zone ◽  
Natural Analogues ◽  
Zeolite Formation ◽  
Hydraulic Gradients ◽  
Short Time

AbstractCement and concrete will be used as fracture grouts, shotcrete, tunnel and borehole seals, and as matrices for waste encapsulationinter aliain geological repositories for radioactive wastes. Alteration of the host rock and/or swelling clay in waste package buffers and tunnel backfills by hyperalkaline solutions from cement/concrete may be deleterious to system performance through changes in the physicochemical properties of these barrier materials.Analogue systems (and timescales) relevant to the understanding of the alkaline disturbed zone include: industrial analogues, such as alkaline flooding of hydrocarbon reservoirs (up to 30 y), cement-aggregate reactions (up to 100 y) and the Tournemire tunnel (up to 125 y); and natural analogues, including the hyperalkaline springs at Maqarin, Jordan (more than 100,000 y), saline, alkaline lakes (more than 1,000,000 y) and certain fracture fillings in granites (more than 1,000,000 y).These systems show that alkaline alteration can be observed for thousands of years over distance scales of hundreds of metres under extreme conditions of hydraulic gradients in fractured rocks (Maqarin), but may be limited to a few centimetres over tens to a hundred years in mudstone (Tournemire). Important reaction mechanisms for retardation of alkaline fluids include: fluid mixing (alkaline oil floods, Maqarin), ion exchange (alkaline oil floods, Tournemire) and kinetic mineral dissolution-precipitation reactions (all systems studied). Qualitative and quantitative kinetic data for mineral reactions are available from cement aggregate reactions and the Searles Lake analogue, respectively. Short-term alteration observed in cement-aggregates is characterized by calcium silicate hydrate (C-S-H) minerals and incipient zeolite formation, whereas evidence from the Tournemire tunnel shows the growth of K-feldspar after relatively short time intervals (tens to a hundred years). There is a tendency for alkaline alteration to result in porosity decreases, but locally, porosity may be enhanced (e.g. near-injection well interactions in alkaline oil floods, or at fracture margins at Maqarin, Jordan). Data from industrial and natural analogues may thus supply some key data for bridging time and space scales between laboratory andin situexperiments on one hand and the requirements for safety assessment on the other.

Modeling of an in-situ diffusion experiment in granite at the Grimsel Test Site

2014 ◽  
Vol 1665 ◽  
pp. 85-91 ◽  
Author(s):  
Josep M. Soler ◽  
Jiri Landa ◽  
Vaclava Havlova ◽  
Yukio Tachi ◽  
Takanori Ebina ◽  
...  
Keyword(s):  
Effective Diffusion ◽  
Test Site ◽  
Diffusion Experiment ◽  
Bulk Rock ◽  
Disturbed Zone ◽  
Mean Grain Size ◽  
Grimsel Test Site ◽  
In Situ Diffusion

ABSTRACTMatrix diffusion is a key process for radionuclide retention in crystalline rocks. Within the LTD project (Long-Term Diffusion), an in-situ diffusion experiment in unaltered non-fractured granite was performed at the Grimsel Test Site (www.grimsel.com, Switzerland). The tracers included 3H as HTO, 22Na+, 134Cs+ and 131I- with stable I- as carrier.The dataset (except for 131I- because of complete decay) was analyzed with different diffusion-sorption models by different teams (NAGRA / IDAEA-CSIC, UJV-Rez, JAEA, Univ. Poitiers) using different codes, with the goal of obtaining effective diffusion coefficients (De) and porosity (ϕ) or rock capacity (α) values. A Borehole Disturbed Zone (BDZ), which was observed in the rock profile data for 22Na+ and 134Cs+, had to be taken into account to fit the experimental observations. The extension of the BDZ (1-2 mm) was about the same magnitude as the mean grain size of the quartz and feldspar grains.De and α values for the different tracers in the BDZ are larger than the respective values in the bulk rock. Capacity factors in the bulk rock are largest for Cs+ (strong sorption) and smallest for 3H (no sorption). However, 3H seems to display large α values in the BDZ. This phenomenon will be investigated in more detail in a second test starting in 2013.

scholarly journals Airborne surface profiling of glaciers: a case-study in Alaska

1996 ◽  
Vol 42 (142) ◽  
pp. 538-547 ◽  
Author(s):  
Κ. A. Echelmeyer ◽  
W. D. Harrison ◽  
C. F. Larsen ◽  
J. Sapiano ◽  
Mitchell J. E. ◽  
...  
Keyword(s):  
Time Intervals ◽  
Glacier Surface ◽  
Alaska Range ◽  
Thickness Change ◽  
Surface Profiling ◽  
Bear Lake ◽  
South Central ◽  
Short Time

AbstractA relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested. The aircraft position is determined by kinematic global positioning system (GPS) methods. The distance to the glacier surface is determined with a laser ranger. The accuracy is about 0.3 m, sufficient to permit future changes to be observed over short time intervals. Long-term changes can be estimated by comparison of profiles with existing maps. Elevation profiles obtained in 1993–94 from three glaciers in central and south-central Alaska are compared with maps made about 1950. The resulting area-averaged, seasonally corrected thickness changes during the interval are: Gulkana Glacier (central Alaska Range)–11 m, Worthington Glacier (central Chugach Mountains) +7 m, and Bear Lake Glacier (Kenai Mountains) −12 m. All three glaciers retreated during the interval of comparison. The estimated uncertainty in the average thickness change is ±5 m. which is mainly due to errors in the existing maps. Constraints on the accuracy of the maps are obtained by profiling in proglacial areas.

scholarly journals Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic

2015 ◽  
Vol 112 (41) ◽  
pp. 12604-12609 ◽  
Author(s):  
Mathieu Martinez ◽  
Guillaume Dera
Keyword(s):  
Carbon Cycle ◽  
Orbital Forcing ◽  
Time Intervals ◽  
Sea Level Fluctuations ◽  
The Past ◽  
Paleoenvironmental Changes ◽  
Chaotic Diffusion ◽  
Orbital Cycles ◽  
Short Time

Eccentricity, obliquity, and precession are cyclic parameters of the Earth’s orbit whose climatic implications have been widely demonstrated on recent and short time intervals. Amplitude modulations of these parameters on million-year time scales induce ‟grand orbital cycles,” but the behavior and the paleoenvironmental consequences of these cycles remain debated for the Mesozoic owing to the chaotic diffusion of the solar system in the past. Here, we test for these cycles from the Jurassic to the Early Cretaceous by analyzing new stable isotope datasets reflecting fluctuations in the carbon cycle and seawater temperatures. Our results document a prominent cyclicity of ∼9 My in the carbon cycle paced by changes in the seasonal dynamics of hydrological processes and long-term sea level fluctuations. These paleoenvironmental changes are linked to a great eccentricity cycle consistent with astronomical solutions. The orbital forcing signal was mainly amplified by cumulative sequestration of organic matter in the boreal wetlands under greenhouse conditions. Finally, we show that the ∼9-My cycle faded during the Pliensbachian, which could either reflect major paleoenvironmental disturbances or a chaotic transition affecting this cycle.

scholarly journals Airborne observations of newly formed boundary layer aerosol particles under cloudy conditions

2018 ◽  
Vol 18 (11) ◽  
pp. 8249-8264 ◽  
Author(s):  
Barbara Altstädter ◽  
Andreas Platis ◽  
Michael Jähn ◽  
Holger Baars ◽  
Janine Lückerath ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ultrafine Particles ◽  
Aerosol Particles ◽  
Inversion Layer ◽  
Time Intervals ◽  
Flight Duration ◽  
Airborne Measurements ◽  
Stratocumulus Clouds ◽  
Short Time

Abstract. This study describes the appearance of ultrafine boundary layer aerosol particles under classical “non-favourable” conditions at the research site of TROPOS (Leibniz Institute for Tropospheric Research). Airborne measurements of meteorological and aerosol properties of the atmospheric boundary layer (ABL) were repeatedly performed with the unmanned aerial system ALADINA (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) during three seasons between October 2013 and July 2015. More than 100 measurement flights were conducted on 23 different days with a total flight duration of 53 h. In 26 % of the cases, maxima of ultrafine particles were observed close to the inversion layer at altitudes between 400 and 600 m and the particles were rapidly mixed vertically and mainly transported downwards during short time intervals of cloud gaps. This study focuses on two measurement days affected by low-level stratocumulus clouds, but different wind directions (NE, SW) and minimal concentrations (< 4.6 µg m−3) of SO2, as a common indicator for precursor gases at ground. Taken from vertical profiles, the onset of clouds led to a non-linearity of humidity that resulted in an increased turbulence at the local-scale and caused fast nucleation (e.g. Bigg, 1997; Wehner et al., 2010), but in relation to rapid dilution of surrounding air, seen in sporadic clusters of ground data, so that ultrafine particles disappeared in the verticality. The typical “banana shape” (Heintzenberg et al., 2007) of new particle formation (NPF) and growth was not seen at ground and thus these days might not have been classified as NPF event days by pure surface studies.

scholarly journals Gamma-Ray Orbital Modulation of the Transitioning Millisecond Pulsar Binary XSS J12270–4859

2022 ◽  
Vol 924 (2) ◽  
pp. 91
Author(s):  
Hongjun An
Keyword(s):  
Gamma Ray ◽  
Optical Data ◽  
Large Area ◽  
Time Intervals ◽  
Optical Telescope ◽  
X Ray ◽  
Low Mass ◽  
Orbital Modulation ◽  
Short Time

Abstract We report on gamma-ray orbital modulation of the transitioning MSP binary XSS J12270–4859 detected in the Fermi Large Area Telescope (LAT) data. We use long-term optical data taken with the XMM-Newton OM and the Swift UltraViolet Optical Telescope to inspect radio timing solutions that are limited to relatively short time intervals and find that extrapolation of the solutions aligns well with the phasing of the optical data over 15 yr. The Fermi-LAT data folded on the timing solutions exhibit significant modulation (p = 5 × 10−6) with a gamma-ray minimum at the inferior conjunction of the pulsar. Intriguingly, the source seems to show similar modulation in both the low-mass X-ray binary and the MSP states, implying that mechanisms for gamma-ray emission in the two states are similar. We discuss these findings and their implications using an intrabinary shock scenario.

scholarly journals How to cross the sea: testing the dispersal mechanisms of the cosmopolitan earthworm Pontodrilus litoralis

2021 ◽  
Vol 8 (8) ◽  
pp. 202297
Author(s):  
Shiao-Yin Chen ◽  
Chia-Hsuan Hsu ◽  
Keryea Soong
Keyword(s):  
Body Parts ◽  
Evolutionary Time ◽  
The West ◽  
Low Latitudes ◽  
The World ◽  
Dispersal Capability ◽  
Phase Out ◽  
Short Time

Dispersal capability often decides the geographical distribution and long-term success of a species. In this investigation, Pontodrilus litoralis , a widely distributed species along shores throughout mid- and low latitudes of the world, was investigated. We tested three hypotheses explaining its dispersal: helped by humans, transported by birds and carried by currents. Although the earthworms seemed to be associated with artificially planted wind-breaking woods and mangroves along the west coast of Taiwan, they were also found on isolated beaches in the Pescadores Islands without such plantings. They are approximately 2 mm wide, making them too small for use as fishing bait. These two mechanisms invoking human help were not supported. In a laboratory experiment, we moved the earthworms to the plumage of various body parts of pigeons, and they dropped off or died within a short time, a result incompatible with the bird hypothesis. The earthworms stayed alive and grew when immersed in freshwater or seawater for at least a month. They also survived on floating wood in an in situ experiment lasting approximately two months. Thus, the current hypothesis was the only one we were unable to falsify; driftwood and perhaps wooden vessels could provide both food and transport on long journeys. Wood boats exist for a short time on an evolutionary time scale, but it may be long enough to disperse the earthworm around the world. The phase-out of wood boats, thus, may start the divergence of P. litoralis populations around the world.

Thorough Testing of Performance Assessment Models: The Necessary Integration of In Situ Experiments, Natural Analogue Studies, and Laboratory Work

1997 ◽  
Vol 506 ◽  
Author(s):  
W. Russell Alexander ◽  
Andreas Gautschi ◽  
Piet Zuidema
Keyword(s):  
Performance Assessment ◽  
Laboratory Experiments ◽  
Field Experiments ◽  
Laboratory Data ◽  
Short Term ◽  
Natural Analogues ◽  
Long Timescales ◽  
Waste Repositories

ABSTRACTRepositories have to isolate radioactive waste (radwaste) and some toxic wastes from the environment for hundreds to hundreds of thousands of years. For many scientists and engineers, and especially the general public, such time spans are beyond comprehension and, consequently, they have grave doubts as to the safety of any such waste repositories. That repository performance over these long time scales can only be assessed by the use of complex mathematical models (normally called performance assessment, or PA, models) only adds to the mistrust of many. How then can people be convinced that it is possible to assess the performance (and thus ensure the safety) of a repository over the long timescales of interest? One way is to address the robustness of the PA models, by clearly indicating the form and extent of model testing carried out within the repository PA. Not only can this show that the individual component parts of the complex structure which constitutes most PA models have been checked, but also that the ‘mathematical black boxes’ constitute an acceptabe representation of the repository system.Part of the problem undoubtedly lies in the unusual nature of radwaste disposal: in most major engineering projects, such as bridge construction or aerospace engineering, the designs are tested against a range of laboratory experiments backed up by expert judgement based on experience with the same or similar systems. Here repository design deviates from standard engineering practice in that no high-level waste (and only a few low- and intermediate-level waste) repositories yet exist and, even when they do, testing their compliance to design limits will be somewhat difficult due to the time scales involved. In addition, the irrational fear of most things radioactive means that most people require some greater form of ‘proof’ that a repository is safe than they are willing to accept for other engineered systems. This being the case, significant additional effort must be expended within the radwaste industry to make it completely clear that the PA models can adequately predict the long-term behaviour of a repository.Traditionally, PA modellers have placed much weight on laboratory data for the construction and testing of PA models and, with only a few exceptions, have not integrated in their PA reports data from natural analogues and in situ experiments. The over-dependence on laboratory data is understandable in that the information is produced under well understood, fully controlled conditions and thus the modellers feel they can place a high degree of confidence in the results obtained. Unfortunately, the full complexity of a repository cannot be re-created in a laboratory and it is necessary to address processes which are influenced by natural heterogeneities, which include large degrees of uncertainty and which operate over very long timescales. In this case, it is necessary to supplement laboratory data with information from in situ field experiments and natural analogues.The advantage of natural analogues over short-term laboratory experiments is that they enable study of repository-like systems which have evolved over the geological timescales of relevance to a radwaste repository safety assessment (rather than the days to months usual in laboratory tests). However, by their very nature, natural analogues often have ill-defined boundary conditions which may be better assessed under the well constrained (if less relevant) conditions of a laboratory. Well designed, realistic in situ field experiments can bridge the gap between the laboratory and natural analogues by offering repository relevant natural conditions with some of the constraints of the laboratory (and intermediate timescales). In short, combining information from the three sources (long-term and realistic, if poorly defined, natural analogues, medium-term, better constrained, in situ field experiments and short-term, less realistic but well defined laboratory studies) can provide greater confidence in the extrapolation of laboratory derived data to repository relevant timescales and conditions.This paper will concentrate on presenting a model testing scheme which both promotes transparency (for the sake of technical peer reviewers and the general public alike) and which aims at a thorough test of PA models. In addition, several recently published PAs will be critically examined and the form, extent and transparency of testing will be discussed with a view to improving confidence in the robustness of the models and thus the perceived safety of specific radwaste repository designs.

scholarly journals A Parsimonious Stochastic Water Reservoir: Schreiber’s 1904 Equation

2010 ◽  
Vol 11 (2) ◽  
pp. 575-578 ◽  
Author(s):  
Klaus Fraedrich
Keyword(s):  
Soil Moisture ◽  
Water Reservoir ◽  
Rainfall Runoff ◽  
Time Intervals ◽  
Full State ◽  
Parsimonious Model ◽  
Short Time ◽  
Small Capacity ◽  
Energy Surplus

Abstract A parsimonious model is presented, leading to Schreiber’s aridity–runoff relation as equilibrium solution of the rainfall–runoff chain. The chain commences with a fast stochastic water reservoir of small capacity, representing interception and wetted ground in short time intervals. It feeds a slow (almost stationary) soil moisture reservoir of large capacity, balancing its runoff after long-term averaging. Parameterizing the fast reservoir’s capacity by the water equivalent of net radiation available for evaporation leads to a biased coin-flip surrogate for its “full” or “empty” states when rainfall is larger or smaller than the capacity. Rainfall surplus from the fast reservoir’s full state feeds the slow (almost stationary) soil moisture reservoir; with the residual evaporating the fast reservoir starts anew as empty. Rainfall below capacity evaporates completely and, leaving the energy surplus for sensible heat, the fast reservoir also starts anew as empty. Employing coin-flip occurrence probabilities from exponentially distributed precipitation yields Schreiber’s formula.

scholarly journals Estimation of Raindrop Size Distribution Parameters Using Lightning Data over West Sumatra

2021 ◽  
Vol 13 (2) ◽  
pp. 92-100
Author(s):  
Faridah Salma ◽  
Marzuki Marzuki ◽  
Hiroyuki Hashiguchi ◽  
Fadli Nauval
Keyword(s):  
Time Interval ◽  
Short Time Interval ◽  
Time Intervals ◽  
Raindrop Size Distribution ◽  
West Sumatra ◽  
Distribution Parameters ◽  
Raindrop Size ◽  
The Tropics ◽  
Short Time

In situ observations of raindrop size distributions (DSDs) are still limited, especially in the tropics. Therefore, this study develops an alternative method to calculate DSD parameters by utilizing lightning data from the World-Wide Lightning Location Network (WWLLN) observation. DSD data was obtained from Parsivel's observations in the equatorial regions of Indonesia, i.e., Kototabang (100.32◦E, 0.20◦S, 865 m above mean sea level/ASL), Padang (100.46°E, 0.915°S, 200 m ASL), and Sicincin (100.30°E, 0.546°S, 134 m ASL). A gamma distribution parameterized the DSD. Three analysis domains were examined, with a grid of 0.1° x 0.1°, 0.5° x 0.5°, and 1° x 1°.  We examined the possibility to calculate the near-instantaneous DSD parameter, so three short time intervals, namely, one, five and ten minutes, were used. The results showed that the number of lightning strokes does not adequately correlate with DSD parameters. This is observed in all time intervals and analysis domains. Thus, the use of lightning data to calculate DSD parameters is not possible for short time interval of DSD (near instantaneous DSD). However, lightning data can estimate the average DSD parameters for an average time of more than one hour, as recommended by previous studies.

Long-term photometric observations in the field of the star formation region NGC7129

2017 ◽  
Vol 13 (S336) ◽  
pp. 287-288
Author(s):  
Evgeni Semkov ◽  
Stoyanka Peneva ◽  
Sunay Ibryamov ◽  
Asen Mutafov
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Variable Stars ◽  
Time Intervals ◽  
Star Formation Region ◽  
Formation Region ◽  
Photometric Observations ◽  
Pms Stars ◽  
Short Time

AbstractWe present results from long-term optical photometric observations of the Pre-Main Sequence (PMS) stars, located in the star formation region around the bright nebula NGC 7129. Using the long-term light curves and spectroscopic data, we tried to classify the PMS objects in the field and to define the reasons for the observed brightness variations. Our main goal is to explore the known PMS stars and discover new, young, variable stars. The new variable PMS star 2MASS J21403576+6635000 exhibits unusual brightness variations for very short time intervals (few minutes or hours) with comparatively large amplitudes (ΔI = 2.65 mag).

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