Quantifying biologically and physically induced flow and tracer dynamics in permeable sediments

Abstract. Insight in the biogeochemistry and ecology of sandy sediments crucially depends on a quantitative description of pore water flow and the associated transport of various solutes and particles. Here, we compare and analyse existing models of tracer dynamics in permeable sediments. We show that all models can be derived from a generic backbone, consisting of the same flow and tracer equations. The principal difference between model applications concerns the geometry of the sediment-water interface and the pressure conditions that are specified along this boundary. We illustrate this commonality with four different case studies. These include biologically and physically induced pore water flows, as well as simplified laboratory set-ups versus more complex field-like conditions: [1] lugworm bio-irrigation in laboratory set-up, [2] interaction of bio-irrigation and groundwater seepage on a tidal flat, [3] pore water flow induced by rotational stirring in benthic chambers, and [4] pore water flow induced by unidirectional flow over a ripple sequence. To illustrate the potential of the generic model approach, the same two example simulations are performed in all four cases: (a) the time-dependent spreading of an inert tracer in the pore water, and (b) the computation of the steady-state distribution of oxygen in the sediment. Overall, our model comparison indicates that model development is promising, but within an early stage. Clear challenges remain in terms of model development, model validation, and model implementation.

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Quantifying biologically and physically induced flow and tracer dynamics in permeable sediments

Biogeosciences ◽

10.5194/bg-4-627-2007 ◽

2007 ◽

Vol 4 (4) ◽

pp. 627-646 ◽

Cited By ~ 36

Author(s):

F. J. R. Meysman ◽

O. S. Galaktionov ◽

P. L. M. Cook ◽

F. Janssen ◽

M. Huettel ◽

...

Keyword(s):

Water Flow ◽

Pore Water ◽

Model Comparison ◽

Early Stage ◽

Model Development ◽

Quantitative Description ◽

Permeable Sediments ◽

Unidirectional Flow ◽

Set Up ◽

Sandy Sediments

Abstract. Insight in the biogeochemistry and ecology of sandy sediments crucially depends on a quantitative description of pore water flow and the associated transport of various solutes and particles. We show that widely different problems can be modelled by the same flow and tracer equations. The principal difference between model applications concerns the geometry of the sediment-water interface and the pressure conditions that are specified along this boundary. We illustrate this commonality with four different case studies. These include biologically and physically induced pore water flows, as well as simplified laboratory set-ups versus more complex field-like conditions: [1] lugworm bio-irrigation in laboratory set-up, [2] interaction of bio-irrigation and groundwater seepage on a tidal flat, [3] pore water flow induced by rotational stirring in benthic chambers, and [4] pore water flow induced by unidirectional flow over a ripple sequence. The same two example simulations are performed in all four cases: (a) the time-dependent spreading of an inert tracer in the pore water, and (b) the computation of the steady-state distribution of oxygen in the sediment. Overall, our model comparison indicates that model development for sandy sediments is promising, but within an early stage. Clear challenges remain in terms of model development, model validation, and model implementation.

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The Emergence of Rabbinic Culture from the Perspective of Qumran

Journal of Ancient Judaism ◽

10.30965/21967954-00602006 ◽

2015 ◽

Vol 6 (2) ◽

pp. 253-274

Author(s):

Vered Noam

Keyword(s):

Early Stage ◽

Second Temple ◽

Test Case ◽

Literary Works ◽

Jewish Culture ◽

The Bible ◽

Set Up

The rabbinic halakhic system, with its many facets and the literary works that comprise it, reflects a new Jewish culture, almost completely distinct in its halakhic content and scope from the biblical and postbiblical culture that preceded it. By examining Jewish legislation in the area of corpse impurity as a test case, the article studies the implications of Qumranic halakhah, as a way-station between the Bible and the Mishnah, for understanding how Tannaitic halakhah developed. The impression obtained from the material reviewed in the article is that the direction of the “Tannaitic revolution” was charted, its methods set up, and its principles established, at a surprisingly early stage, before the destruction of the Second Temple, and thus at the same time that the Qumran literature was created.

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Sampling pore water at a centimeter resolution in sandy permeable sediments of lakes, streams, and coastal zones

Limnology and Oceanography Methods ◽

10.1002/lom3.10408 ◽

2020 ◽

Author(s):

Pierre Anschutz ◽

Céline Charbonnier

Keyword(s):

Pore Water ◽

Coastal Zones ◽

Permeable Sediments

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Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

Hydrology and Earth System Sciences ◽

10.5194/hess-19-2617-2015 ◽

2015 ◽

Vol 19 (6) ◽

pp. 2617-2635 ◽

Cited By ~ 48

Author(s):

M. Sprenger ◽

T. H. M. Volkmann ◽

T. Blume ◽

M. Weiler

Keyword(s):

Soil Moisture ◽

Stable Isotope ◽

Solute Transport ◽

Water Flow ◽

Pore Water ◽

Pedotransfer Functions ◽

Transport Parameters ◽

Soil Moisture Dynamics ◽

Moisture Dynamics ◽

Water Isotope

Abstract. Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last 2 decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by solving the Richards equation numerically with the finite-element code of HYDRUS-1D. The transport of deuterium was simulated with the advection-dispersion equation, and a modified version of HYDRUS was used, allowing deuterium loss during evaporation. The Mualem–van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a), using only the pore water isotope content, cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c), using both the isotope profiles and the soil moisture time series, resulted in good simulation results with regard to the Kling–Gupta efficiency and good parameter identifiability. However, approach (b) has the advantage that it considers the isotope data not only for the solute transport parameters but also for water flow and root water uptake, and thus increases parameter realism. Approaches (b) and (c) both outcompeted simulations run with parameters derived from pedotransfer functions, which did not result in an acceptable representation of the soil moisture dynamics and pore water stable isotope composition. Overall, parameters based on this new approach that includes isotope data lead to similar model performances regarding the water balance and soil moisture dynamics and better parameter identifiability than the conventional inverse model approaches limited to hydrometric fitting targets. If only data from isotope profiles in combination with textural information is available, the results are still satisfactory. This method has the additional advantage that it will not only allow us to estimate water balance and response times but also site-specific time variant transit times or solute breakthrough within the soil profile.

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Relaxometry Models Compared with Bayesian Technique: Ganglioside Micelle Example

10.26434/chemrxiv.12975014 ◽

2020 ◽

Author(s):

Pär Håkansson

Keyword(s):

Model Comparison ◽

Spin Dynamics ◽

Model Development ◽

Relaxation Dispersion ◽

Site Model ◽

Research Areas ◽

Bayesian Model Comparison ◽

Physico Chemical ◽

Complex Liquids ◽

Bayesian Evidence

<div> <div> <div> <p>In this work a methodology to perform Bayesian model-comparison is developed and exemplified in the analysis of magnetic relaxation dispersion (NMRD) experiments of water in Ganglioside micelle system. The NMRD powerful probe of slow dynamics in complex liquids is obtained. There are many interesting systems to study with NMRD, such as ionic and Lyotropic liquids or electrolytes. However, to progress in the understanding of the physical chemistry of studied systems relatively detailed theoretical NMRD-models are required. To improve the models they need to be carefully compared, in addition to physico-chemical considerations of molecular and spin dynamics. The comparison is performed by computing the Bayesian evidence in terms of a thermodynamic integral solved with Markov chain Monte Carlo. The result leads to a conclusion of two micelle water sites, and rules out lower and higher complexity level, i.e., one and three sites. In contrast, and provided only with the quality of best fit, suggest a three site model. The two approximate selection tools, Akaike and Baysian information criterions, may lead to wrong conclusions compared to the the full integration. The methodology is expected to be one of several important tools in NMRD model development, however, is completely general and should find awakened use in many research areas. </p> </div> </div> </div>

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What counts in preschool number knowledge? A Bayes factor analytic approach towards theoretical model development

10.31234/osf.io/kn7j6 ◽

2017 ◽

Author(s):

Yi Mou ◽

Ilaria Berteletti ◽

Daniel C. Hyde

Keyword(s):

Individual Differences ◽

Model Comparison ◽

Bayes Factor ◽

Model Development ◽

Language Abilities ◽

Numerical Ability ◽

Selection Strategies ◽

Bayesian Model Comparison ◽

Mathematics Knowledge ◽

Number Knowledge

Preschool children vary tremendously in their numerical knowledge and these individual differences strongly predict later mathematics achievement. To better understand the sources of these individual differences, we measured a variety of cognitive and linguistic abilities motivated by previous literature to be important and then analyzed which combination of these variables best-explained individual differences in actual number knowledge. Through various data-driven Bayesian model comparison and selection strategies on competing multiple regression models, our analyses identified five variables of unique importance to explaining individual differences in preschool children’s symbolic number knowledge: knowledge of the count list, non-verbal approximate numerical ability, working memory, executive conflict processing, and knowledge of letters and words. Further our analyses revealed that knowledge of the count list, likely a proxy for explicit practice or experience with numbers, and non-verbal approximate numerical ability were much more important to explaining individual differences in number knowledge than general cognitive and verbal abilities. These findings suggest that children bring a diverse set of number-specific, general cognitive and language abilities that are involved in children’s learning of mathematics knowledge, and further suggest that number-specific abilities overshadow more general ones in their contribution to children’s early learning of symbolic numbers.

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