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  • 1
    Electronic Resource
    Electronic Resource
    Quantification of physical ripening in an unripe marine clay soil
    Amsterdam : Elsevier
    Geoderma 58 (1993), S. 67-77 
    Details
    ISSN: 0016-7061
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0016-7061(93)90085-Y
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  • 2
    Electronic Resource
    Electronic Resource
    Simulating water and nitrogen behaviour in soils cropped with winter wheat (1991)
    Springer
    Nutrient cycling in agroecosystems 27 (1991), S. 233-243 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen transport ; crop production ; moisture retention characteristic ; ammonia adsorption ; simulation ; organic N transformations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The SWATNIT model [26], predicting water and nitrogen transport in cropped soils, was evaluated on experimental data of winter wheat for different N treatments. The experiments were monitored at three different locations on different soil types in the Netherlands. Crop growth was simulated using the SUCROS model [11] which was integrated in the SWATNIT model. Both water and nitrogen stress were incorporated. Except for the soil hydraulic properties, all model parameters were taken from literature. The model performance was evaluated on its capability to predict soil moisture profiles, nitrate and ammonia profiles, the time course of simulated total dry matter production and LAI; and crop N-uptake. Results for the simulations of the soil moisture profile indicate that the soil hydraulic properties did not reflect the actual physical behaviour of the soil with respect to soil moisture. Good agreement is found between the measured and simulated nitrate and ammonia profiles. The simulation of the nitrate content of the top layer at Bouwing was improved by increasing the NH 4 + -N-distribution coefficient thereby improving the simulation of the NH 4 + -N-content in this layer. Deviations between simulated and measured nitrate concentrations also occurred in the bottom layers (60–100 cm) of the soil profile. The phreatic ground water might influence the nitrate concentrations in the bottom layers. Concerning crop growth modelling, improvements are needed with respect to the partitioning of total dry matter production over the different plant organs in function of the stress, the calculation of the nitrogen stress and the total nitrogen uptake of the crop through a better estimate of the N-demand of the different plant organs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051130
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  • 3
    Electronic Resource
    Electronic Resource
    Asymptotic Analysis of Solute Transport with Linear Nonequilibrium Sorption in Porous Media (1999)
    Springer
    Transport in porous media 36 (1999), S. 189-210 
    Details
    ISSN: 1573-1634
    Keywords: solute transport ; sorption ; nonequilibrium processes ; asymptotic analysis ; analytical solutions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We analysed the asymptotic behaviour of breakthrough curves (BTCs) obtained after a single pulse injection in a 1D flow domain. Five different types of solute transport with nonequilibrium sorption were considered. The properties of the porous medium were assumed to be spatially constant. For long times, the concentration at a fixed position in time was found to decay like exp(−βt) where β depends on both the transport parameters and the parameters describing the nonequilibrium process. The results from the asymptotic analysis were compared with 1D numerical transport calculations. For all cases examined a good agreement between numerical calculations and the asymptotic analysis was found. The results from the asymptotic analysis provide an alternative way to determine transport and sorption related parameters from BTCs. The derived relationships between β and the model parameters are however only valid for large times. This requires that the very low concentrations need to be measured and not only the bulk mass, too. By either increasing or decreasing the velocity during BTC experiments additional asymptotic equations are obtained which can be used to determine the value of the model parameters. The results from the asymptotic analysis can also be used in standard inverse modelling techniques to either obtain good initial guesses or to reduce the parameter space. The fact that linear nonequilibrium processes decay like exp(−βt) can be used to qualitatively evaluate observed BTCs. The asymptotic analysis can also be easily extended to a larger class of transport problems (e.g. transport of solutes with microbial decay) provided that the overall transport problem remains linear in the concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006553713516
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of the macrodispersive parameters of a motion in a two-layer porous medium (1998)
    Springer
    Acta mechanica 129 (1998), S. 117-126 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper develops a method for deriving good estimates of macrodispersive transport parameters describing the asymptotic evolution of a non-reactive chemical pollutant injected into a two-layer porous medium. These parameters are extracted from the coefficients of asymptotic time-polynomial expansions of some adequately chosen integral transforms performed upon the solution of the original transport problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379654
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  • 5
    Electronic Resource
    Electronic Resource
    Asymptotic solutions for two-site non-equilibrium transport (1998)
    Springer
    Acta mechanica 129 (1998), S. 127-132 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The steepest descent method is used to ascertain the large-time behavior of solute concentrations in homogeneous porous media as determined by advection, diffusion and adsorption-desorption processes; it is found that linear non-equilibrium processes do not, asymptotically, affect the characteristic dispersion length of the transport medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01379655
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Simple Linear Model for Calibration of Time Domain Reflectometry Measurements on Solute Concentration (1998)
    Springer
    Soil Science Society of America journal 62 (1998), S. 83-89 
    Details
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: ws ) in a series-coupled pathway with electrical conductivity in the mobile phase of soil solution (ECwc) in a continuous pathway. We related bulk soil electrical conductivity (ECa) to electrical conductivity of soil water (ECw), assuming constant ECws during breakthrough. This resulted in a linear relationship between ECa and ECw. The linear relation, termed here simple linear model (SLM), was tested using experimental data obtained from soil columns. Laboratory breakthrough experiments were performed on short and large columns by applying a pulse input of solute. At the end of breakthrough, separate calibration experiments were performed using a step input of solute. Both RM and SLM were compared with the step input calibration method (SIM) as a reference method. Results show that the SLM is better than RM in terms of mass recovery. In addition, parameters of the solute transport model were not affected within 20% of uncertainty in the slope coefficient of the SLM when compared with the reference method. Advantages of the SLM are that it has an identical equation form to the SIM but less effort is required, especially for soil columns showing preferential flow, and it can be readily applied to field conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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