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1
HYDROGEOCHEMICAL PROCESSES
ASSOCIATED WITH
SEAWATER INTRUSION
I. Seawater intrusion experiments in laboratory columns
II. Determination of hydrodynamic parameters
III. Analyzing reactive proceses during seawater intrusion
Departamento de Ingeniería Química
Nuria Boluda Botella
PART 2
Seawater intrusion experiments in laboratory columnsNuria Boluda Botella (1994). “Estudio hidrogeoquímico de la intrusión marina.
Simulación experimental y desarrollo de un modelo teórico”. Tesis Doctoral. University of Alicante.
Porous medium
Equilibrium with fresh waterFresh water Fresh water
Sea water
Sea water
Sea water
Sea water Sea water
Sample
Reservoir
Filter
HPLC pump
Pressuregauge
Thermostated column
Thermostatic bath
Seawater intrusion experiments in laboratory columns
Experimental configuration for the column experiments
Seawater intrusion experiments in laboratory columnsVicente Pascual Cases López (2009). “Estudios de procesos de transporte del alquilbenceno
sulfonato lineal en la zona saturada mediante columnas de laboratorio”. DEA. University of Alicante
Seawater intrusion experiments in laboratory columns
Materials (Boluda-Botella, 1994)
Ion Fresh water Sea water
mg/L mmol/L mg/L mmol/L
Na+ 50 2.17 12000 522
K+ 3.4 0.0872 400 10.3
Ca2+ 125 3.13 450 11.3
Mg2+ 15 0.617 1500 61.7
Cl- 105 2.96 21500 606
SO42- 165 1.72 2900 30.2
HCO3- 200 3.28 130 2.13
Characteristics of the natural sediment
Composition %
Calciumcarbonate
53
Quartz 35
Clay 12
CEC 7 meq/100g
Composition of the synthetic freshwater and seawater
Seawater intrusion experiments in laboratory columns
Methods (Boluda-Botella, 1994)
Parameters analyzed:
ChlorideSulfateBicarbonatepHSodiumPotasiumCalciumMagnesium
Continuously sampling at the output of the column
The average results of analysis of pore solution and the exchange complex composition
Natural sediment Treated sediment
Pore solution
(mmol/L)
Exchange complex
(meq/100g)Pore solution
(mmol/L)
Exchange complex
(meq/100g)
CEC 7 10
Na 2.29 0.09 2.20 0.25
K 0.07 0.10 0.09 0.13
Ca 3.03 5.71 3.05 8.35
Mg 1.08 1.10 1.28 1.27
Cl 3.67 3.70
S 1.84 1.97
TIC 3.32 3.40
Study of the cation exchange in batch experiments(Boluda-Botella et al., 2008)
Seawater intrusion experiments in laboratory columns
Longitudinal dispersion of a tracer passing through a column of porous medium; a) Columnwith steady flow and continuous supply of tracer after time t0; b) Step-function-type tracerinput; c) Relative tracer concentration in outflow from column (dashed line indicates plugflow condition and solid line ilustrates effect of mechanical dispersion and moleculardiffusion; d) concentration profile in the column at various times (Freeze and Cherry, 1979).
Determination of hydrodynamic parameters
Determination of hydrodynamic parameters
0 100 200 300 400 500
Time (h)
0
100
200
300
400
500
600
700
Chl
orid
e (m
mol
/l)
Experiment I
Experiment II
C = [Cl]t = timex = distance
Numerical model applied to experimental data (Gomis et al., 1997)
u = Darcy velocitye= porosityDL = dispersion coefficient
2
2
LxCD
xCu
tC
Determination of hydrodynamic parameters
The variation of the concentration of tracer versus the time can be determined with theanalytical solution of the equation:
where C represents the concentration of the solute, x the distance, t the time, DL is thehydrodynamic dispersion and v is the interstitial velocity.
If we consider a semi-infinite column from x = 0 to x =∞, with a constant concentration at
the inlet, with the boundary condition, x = 0 , , the obtained equation is(Lapidus y Amundson, 1952):
2
2
LxCD
xCv
tC
t4Dvtxerfc
Dvxexp
t4Dvtxerfc
2)C(CCt)C(x,
LLL
i0i
)C0)t(C(0, 0
Analytical equation to calculate transport parameters
Determination of hydrodynamic parameters
The software, available in http://hdl.handle.net/10045/2691, was developed in theChemical Engineering Department of the University of Alicante. It use the analyticalsolution proposed by Lapidus and Amundson (1952).
ACUAINTRUSION TRANSPORT software
Determination of hydrodynamic parameters
The software calculate the best fit to the experimental data. From this, the program obtainthe transport parameters (Boluda-Botella et al., 2010).
ACUAINTRUSION TRANSPORT software
Experimental chloride breakthrough curve (symbol) obtained in experiment I (Q=20mg/min), experiment II (Q=35 mg/min), experiment A (Q=82 mg/min) and experiment B(Q=20 mg/min, treated sediment) versus experimental time (h).
Best fit of the experimental data (continuous line) obtained with the analytical solution ofthe convection-dispersion equation of ACUAINTRUSION TRANSPORT (T=theoretical).
0
100
200
300
400
500
600
700
0 100 200 300 400
Time (h)
Chl
orid
e (m
mol
/L)
Exp. I
T Exp. I
Exp. II
T Exp. II
Exp. A
T Exp. A
Exp. B
T Exp. B
(a)
Determination of hydrodynamic parameters
Determination of hydrodynamic parameters
Q = flow rateu = Darcy velocitytm = average time of residencePe = Péclet number
Exp. Q(mg/min)
Porousmedia
u(cm/h)
tm(h)
Pe=vL/DL e v(cm/h)
DL(cm2/h)
a(cm)
I 20 Natural 0.15 241 183 0.37 0.41 0.23 0.55
II 35 Natural 0.27 143 166 0.38 0.70 0.42 0.60
A 82 Natural 0.63 65 5.6 0.41 1.54 27.3 17.7
B 20 Treated 0.15 203 147 0.31 0.49 0.33 0.68
The following parameters were determined with ACUAINTRUSION TRANSPORT
e= effective porosityv = interstitial velocityDL = dispersion coefficienta = dispersivity
Experimental chloride breakthrough curve (symbol) for the experiments versus experimental dimensionless time (time/tm). (Boluda-Botella el al., 2008)
0
100
200
300
400
500
600
700
0 0.5 1 1.5 2 2.5 3
Dimensionless time
Chlo
ride
(mm
ol/L
)
Exp. IExp IIExp. AExp. B
(b)
Determination of hydrodynamic parameters
17
REFERENCES
Boluda-Botella, N. 1994. Estudio hidrogeoquímico de la intrusión marina. Simulación experimental ydesarrollo de un modelo teórico. Tesis de Doctoral. Universidad de Alicante.
Boluda-Botella, N., Gomis Yagües, V. and Ruiz Beviá, F. 2008. Influence of the transport parametersand chemical properties of the sediment in experiments to measure reactive transport in seawaterintrusion. J. of Hydrol. 357: 29-41.
Boluda-Botella, N., León, V.M., Cases, V., Gomis, V. and Prats, D. 2010. Fate of linear alkylbenzenesulfonate in agricultural soil columns during inflow of surfactant pulses. J. of Hydrol., 395: 141-152.
Cases López, V.P. 2009. Estudios de procesos de transporte del alquilbenceno sulfonato lineal en lazona saturada mediante columnas de laboratorio. DEA. Universidad de Alicante.
Egea Llopis, E. 2009. Estudios de transporte reactivo de contaminantes en zona saturada:experimentos de inyección de LAS en columna y modelización con PHREEQC. Proyecto Fin de Carrera.Universidad de Alicante.
Freeze, R.A. and Cherry, J.A. 1979. Groundwater. Prentice Hall, Inc.
Gomis, V., Boluda, N., Ruiz, F. 1997. Column displacement experiment to validate hydrogeochemicalmodels of seawater intrusions. J. Cont. Hydrol. 29: 81–91.
Lapidus, L., and Amundson, N.R. 1952. Mathematics of adsorption in beds. VI. The effect oflongitudinal diffusion in ion exchange and chromatographic columns. J. Phys. Chem. 56: 984-988.