scholarly journals Hydrodynamic dispersion characteristics of lateral inflow into a river tested by a laboratory model

2009 ◽  
Vol 13 (2) ◽  
pp. 217-228 ◽  
Author(s):  
P. Y. Chou ◽  
G. Wyseure
Keyword(s):  
Pore Water ◽  
Transport Model ◽  
Column Experiment ◽  
Breakthrough Curves ◽  
Water Velocity ◽  
Laboratory Model ◽  
Hydrodynamic Dispersion ◽  
Transport Parameter ◽  
Transport Parameters ◽  
Pore Water Velocity

Abstract. Groundwater and river-water have a different composition and interact in and below the riverbed. The riverbed-aquifer flux interactions have received growing interest because of their role in the exchange and transformation of nutrients and pollutants between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical transport model, which includes the unsaturated recharge zone, the aquifer and the riverbed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation for every flux on individual segments to the observed breakthrough curves of the resident concentration, and by inverse modelling for every flux simultaneously over the entire flow domain. The obtained transport-parameter relation was tested by numerical simulation using HYDRUS 2-D/3-D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of riverbed-aquifer flux interaction should take this into account.

scholarly journals Lateral inflow into the hyporheic zone tested by a laboratory model

2008 ◽  
Vol 5 (3) ◽  
pp. 1567-1601 ◽  
Author(s):  
P. Y. Chou ◽  
G. Wyseure
Keyword(s):  
Pore Water ◽  
Hyporheic Zone ◽  
Column Experiment ◽  
Breakthrough Curves ◽  
Water Velocity ◽  
Hyporheic Exchange ◽  
Laboratory Model ◽  
Transport Parameters ◽  
Pore Water Velocity ◽  
River Bed

Abstract. Groundwater and river water with a different composition interact and exchange in the hyporheic zone. The study of hyporheic zone and its impact on water quality has recently received growing interest because of its role in nutrients and pollutants interactions between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical model, which include the unsaturated recharge zone, the aquifer and the river bed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation on individual segments to the observed resident breakthrough curves, and by inverse modelling on the entire flow domain for every flux. The obtained transport parameters relation was tested by numerical simulation using HYDRUS 2D/3D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of the hyporheic exchange of the water and dissolved materials should take this into account.

Estimation of hydrodynamic dispersion in a fine sand using an approximate analytical solution

Soil Research ◽  
1981 ◽  
Vol 19 (3) ◽  
pp. 265 ◽  
Author(s):  
KK Watson ◽  
MJ Jones
Keyword(s):  
Analytical Solution ◽  
Pore Water ◽  
Numerical Solutions ◽  
Approximate Analytical Solution ◽  
Fine Sand ◽  
Water Velocity ◽  
Hydrodynamic Dispersion ◽  
Pore Water Velocity ◽  
Predictive Quality ◽  
Computer Based

The quasi-analytical approach to hydrodynamic dispersion during horizontal absorption under constant concentration conditions is discussed, and it is shown that the pore water velocity reaches a maximum at the � value where g(�) =0. The resulting small variations in pore water velocity that occur across the solute front and the relative constancy of water content in that region during absorption in a fine sand allow an approximate analytical solution for velocity-dependent hydrodynamic dispersion to be formulated. The equation is tested against computer-based numerical solutions for both horizontal absorption and vertical infiltration. The predictive quality of the approximate analytical solution is found to be very good for the systems examined.

scholarly journals Identification of transport parameters of chlorides in different soils on the basis of column studies

Geologos ◽  
2019 ◽  
Vol 25 (3) ◽  
pp. 225-229
Author(s):  
Damian Pietrzak ◽  
Jarosław Kania ◽  
Ewa Kmiecik ◽  
Katarzyna Wątor
Keyword(s):  
Pore Water ◽  
Dispersion Coefficient ◽  
Fine Sand ◽  
Water Velocity ◽  
Silty Sand ◽  
Column Experiments ◽  
Transport Parameters ◽  
Column Studies ◽  
Pore Water Velocity ◽  
Different Soils

Abstract Knowledge of transport patterns of chemicals in groundwater is essential for environmental assessment of their potential impact. In the present study, the mobility of a chloride tracer injected into three different soils was investigated, using column experiments. The column tests were performed under steady-state conditions to determine parameters of chloride migration through soils. Based on breakthrough curves, pore-water velocity, dispersion coefficient and dispersivity constant were calculated for each soil sample using CXTFIT/STANMOD software. Pore-water velocity was in the range of 0.31 cm/min for fine sand, to 0.35 cm/min for silty sand and to 0.40 cm/min for vari-grained sand. The highest values of dispersion coefficient and dispersivity constant were observed for silty sand (0.55 cm2/min and 1.55 cm, respectively), while the lowest value was found for fine sand (0.059 cm2/min and 0.19 cm, respectively). Column experiments for chlorides (conservative tracer) are a preliminary stage for further research which will be undertaken to investigate migration parameters of selected neonicotinoids (reactive tracers) through different soils.

Site-Specific Management of Flow and Transport in Homogeneous and Structured Soils

1999 ◽  
Author(s):  
D. J. Mulla ◽  
A. P. Mallawatantri
Keyword(s):  
Hydraulic Conductivity ◽  
Spatial Variability ◽  
Solute Transport ◽  
Pore Water ◽  
Water Velocity ◽  
Soil Science ◽  
Hydrodynamic Dispersion ◽  
Field Scale ◽  
Frequency Distributions ◽  
Pore Water Velocity

Among research publications in soil science, few have had a greater impact than those by Nielsen et al. (1973) or Biggar and Nielsen (1976). According to Science Citation Index, the former paper, entitled “Spatial variability of field-measured soilwater properties,” has been cited by scientific peers over 390 times. The 1976 paper, entitled “Spatial variability of the leaching characteristics of a field soil,” has been cited over 232 times. Experimental work presented in both papers represents the first-ever attempt at a large field-scale study of steady-state water and solute transport (Wagenet, 1986). Among the seminal findings of these two papers were as follows: (1) extensive spatial variability existed in soil hydraulic and solute transport properties within a relatively homogeneous field (important in the work of Pilgrim et al., 1982; Addiscott and Wagenet, 1985; Feddes et al., 1988; van dcr Molen and van Ommen, 1988); (2) soil water content, bulk density, and soil particle size exhibited normal frequency distributions, while distributions for hydraulic conductivity, hydraulic diffusivity, pore water velocity, and hydrodynamic dispersion were lognormal (work extended by van der Pol et al.. 1977; Rao et al., 1979); (3) frequency distributions were far superior to field-average parameter values (especially for lognormally distributed properties) in describing field transport behavior (demonstrated by Rao et al., 1979; Trangmar et al., 1985); (4) a simple unit hydraulic gradient method was shown to estimate saturated hydraulic conductivity accurately (results extended by Libardi et al., 1980; van Genuchten and Leij, 1992); (5) good correspondence was found between solute velocity and pore water velocity (key assumption in Jury and Fluhler, 1992); (6) and theoretical predictions of a linear relation between hydrodynamic dispersion and pore water velocity were shown to be obeyed at the field scale (result used widely by solute transport modelers, as discussed in Nielsen et al., 1986). The seminal works by Nielsen et al. (1973) and Biggar and Nielsen (1976) produced several new directions in soil science and vadose zone hydrology research. The most interesting was a series of papers that rejected the theoretical basis and practicality of using deterministic equations, and instead introduced stochastic approaches to describe field-scale water and solute fluxes.

Effects of zeolite application on nitrate and ammonium retention of a loamy soil under saturated conditions

Soil Research ◽  
2007 ◽  
Vol 45 (5) ◽  
pp. 368 ◽  
Author(s):  
A. R. Sepaskhah ◽  
F. Yousefi
Keyword(s):  
Pore Water ◽  
Breakthrough Curve ◽  
Application Rate ◽  
Exchange Capacity ◽  
Water Velocity ◽  
Ammonium Concentration ◽  
Soil Conditions ◽  
Hydrodynamic Dispersion ◽  
Pore Water Velocity ◽  
The Relationship

Nitrogen (N) loss from irrigated cropland, especially in rice paddies, results in low N-use efficiency and groundwater contamination. Soil conditions that increase ammonium and nitrate ion retention alleviate these problems. Clinoptilolite, a naturally occurring zeolite with high-exchange capacity, may be used to absorb ammonium and retard excess leaching of nitrate. The objectives of this research were to determine the effects of different rates of Ca–K-zeolite application (0, 2, 4, and 8 g/kg soil) on pore water velocity and leaching of ammonium and nitrate applied as ammonium nitrate fertiliser to a loam soil at a rate of 350 kg N/ha under saturated conditions similar to that of a rice paddy. The results indicate that Ca–K-zeolite applications of 4 and 8 g/kg soil increase the pore water velocity by 35% and 74%, respectively. The maximum relative concentration (c/co) for the nitrate breakthrough curve occurring at pore volume of about 0.5 was reduced by 15% with a zeolite application rate of 8 g/kg soil. When applying 40 cm of leaching water, leached nitrate was 75% and 63% of total applied nitrate at the soil surface with zeolite applications of 4 and 8 g/kg soil, respectively. Due to the high ion exchange capacity of zeolite, the application of zeolite at 2 g/kg soil is enough to increase the exchange sites in the soil in order to absorb the applied ammonium and prevent its leaching by the inflow water. The maximum ammonium concentration in the breakthrough curve for the zeolite application rate of 2 g/kg soil was reduced by 43% compared with the control treatment. The relationship between the hydrodynamic dispersion coefficient (D) for nitrate and pore water velocity (v) was not linear and it was correlated with squared pore water velocity. The coefficient of the relationship between D and v2 was dependent on the zeolite application rate and linearly increased with this rate.

scholarly journals Quantification of pore-size spectrums by solute breakthrough curves

2011 ◽  
Vol 8 (5) ◽  
pp. 8373-8397
Author(s):  
S. Erşahin
Keyword(s):  
Particle Size ◽  
Porous Medium ◽  
Pore Size ◽  
Pore Water ◽  
Pore Radius ◽  
Total Porosity ◽  
Breakthrough Curves ◽  
Water Velocity ◽  
Size Spectrum ◽  
Pore Water Velocity

Abstract. Breakthrough of conservative tracers may be used to quantify pore-size spectrum and pore-water velocity distributions in a porous medium. In this study, a theory was proposed to calculate pore-water velocity and corresponding pore-size spectrum in porous media, and its application was demonstrated. Miscible displacement tests of chloride were conducted with sand columns (5 cm id and 5 cm length), repacked with washed sand with a particle size of 2–1, 1–0.45, 0.45–0.325 and <0.325 mm in diameter. The resulting breakthrough curves were divided into approximately 20 segments, and for each segment, a concentration of Cl in an out-flowing effluent was used with corresponding effluent volume and travel time to calculate corresponding pore water velocity (v) and pore-radius. Mean v (vb) calculated for a column was approximated by geometric averaging the calculated v-values for the BTC. To validate the developed model, laboratory measured and approximated values of vb were compared. The correlation analysis conducted between measured and approximated vb resulted in a correlation coefficient of r = 0.89 (P < 0.01). The results revealed that size distribution of effective pores could be quite different even in replicates of small sand columns, which are highly similar in particle-size and total porosity.

Experimental and numerical investigation of microparticle transport and deposition in the context of permafrost thaw

2021 ◽  
Author(s):  
Madiha Khadhraoui ◽  
John Molson ◽  
Najat Bhiry
Keyword(s):  
Porous Media ◽  
Pore Water ◽  
Water Velocity ◽  
Kinetic Term ◽  
Column Experiments ◽  
Order Kinetic ◽  
Permafrost Degradation ◽  
Pore Water Velocity ◽  
Laboratory Column ◽  
Study Laboratory

&lt;p&gt;In natural porous environments, soil particle migration during flow plays an important role in soil stability and pollutant transport by affecting soil mechanical properties and water quality. In northern areas, permafrost degradation alters the subsurface connection pathways leading to mass movements and rearrangement of the soil. To date, few models have included the influence of temporal and spatial variations of flow velocity and porous media heterogeneity on the transport and deposition of suspended particles.&lt;/p&gt;&lt;p&gt;In this study, laboratory column experiments and a numerical model were used to investigate these issues. The laboratory column experiments were carried out under different flow rates and the effect of porous media heterogeneity was investigated using different grain size distributions. The soil columns were reconstituted from several samples taken in the studied site, the Tasiapik Valley, located in the discontinuous permafrost zone near Umiujaq, Nunavik, Qu&amp;#233;bec. During the experiments, the spatio-temporal distribution of the porosity and the hydraulic conductivity was monitored using X-ray computed tomography imaging (CT-SCAN). Using the pore water velocity computed from the groundwater flow solution, the advection&amp;#8211;dispersion transport equation with a first-order kinetic term for particle deposition was solved using the finite element model Heatflow/Smoker. The dependency of the attachment kinetics on the pore water velocity and on the porous media heterogeneity was included. The model was tested and validated with an analytical solution and calibrated with the experimental data. Our simulations highlight the roles of hydrodynamic conditions and soil characteristics on particle transport and deposition mechanisms and the susceptibility of the porous medium to thermo-suffosion in permafrost environments.&lt;/p&gt;

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