Comparison of the performance of traditional advection-dispersion equation and mobile-immobile model for simulating solute transport in heterogeneous soils

Abstract

The traditional advection-dispersion equation (ADE) and the mobile-immobile model (MIM) are widely used to describe solute transport in heterogeneous porous media. However, the fitness of the two models is case-dependent. In this paper, the transport of conservative, adsorbing and degradable solutes through a 1 m heterogeneous soil column under steady flow condition was simulated by ADE and MIM, and sensitivity analysis was conducted. Results show that MIM tends to prolong the breakthrough process and decrease peak concentration for all three solutes, and tailing and skewness are more pronounced with increasing dispersivity. Breakthrough curves of the adsorbing solute simulated by MIM are less sensitive to the retardation factor compared with the results simulated by ADE. The breakthrough curves of degradable solute obtained by MIM and ADE nearly overlap with a high degradation rate coefficient, indicating that MIM and ADE perform similarly for simulating degradable solute transport when biochemical degradation prevails over the mass exchange between mobile and immobile zones. The results suggest that the physical significance of dispersivity should be carefully considered when MIM is applied to simulate the degradable solute transport and/or ADE is applied to simulate the adsorbing solute transport in highly dispersive soils.

Keywords

solute transport / advection dispersion equation (ADE) / mobile-immobile model (MIM) / conservative solute / adsorbing solute / degradable solute / PHREEQC-2

References

[1] Beven K, Germann P. Macropores and water flow in soils. Water Resources Research, 1982, 18(5): 1311–1325

[2] Porro I, Wierenga P J. Transient and steady-state solute transport through a large unsaturated soil column. Ground Water, 1993, 31(2): 193–200

[3] Pace M N, Mayes M A, Jardine P M, Mehlhorn T L, Zachara J M, Bjornstad B N. Quantifying the effects of small-scale heterogeneities on flow and transport in undisturbed cores from the hanford formation. Vadose Zone Journal, 2003, 2(4): 664–676

[4] Stagnitti F, Li L, Barry D A, Allinson G, Parlange J Y, Steenhuis T, Lakshmanan E. Modelling solute transport in structured soils: performance evaluation of the ADR and TRM models. Mathematical and Computer Modelling, 2001, 34(3–4): 433–440

[5] Rosqvist H, Destouni G. Solute transport through preferential pathways in municipal solid waste. Journal of Contaminant Hydrology, 2000, 46(1–2): 39–60

[6] Jiang Y, Zhou B, Shao M, Wang Q. Experimental study on preferential solute transport in a loess plateau soil. Australian Journal of crop science, 2013, 7(1): 93–98

[7] Gao G, Zhan H, Feng S, Huang G, Mao X. Comparison of alternative models for simulating anomalous solute transport in a large heterogeneous soil column. Journal of Hydrology, 2009, 377(3–4): 391–404

[8] Vaughan P J, Shouse P J, Suarez D L, Ayars J E. Analysis of field scale salinization: a comparison of different modeling approaches. Journal of hydrology and hydromechanics, 2005, 53(2): 73–90

[9] Li Y, Ghodrati M. Preferential transport of nitrate through soil columns containing root channels. Soil Science Society of America Journal, 1994, 58(3): 653–659

[10] Abbasi F, Feyen J, van Genuchten M T. Two-dimensional simulation of water flow and solute transport below furrows: model calibration and validation. Journal of Hydrology (Amsterdam), 2004, 290(1–2): 63–79

[11] Parkhurst D L, Appelo C AJ. User’s guide to PHREEQC (Version 2): a computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. Denver: U.S. Geological Survey Water-Resources Investigations, 1999

[12] Spiteri C, Slomp C P, Regnier P, Meile C, Van Cappellen P. Modelling the geochemical fate and transport of wastewater-derived phosphorus in contrasting groundwater systems. Journal of Contaminant Hydrology, 2007, 92(1–2): 87–108

[13] De Smedt F, Wierenga P J. Mass transfer in porous media with immobile water. Journal of Hydrology, 1979, 41(1–2): 59–67

[14] Vanderborght J, Vanclooster M, Timmerman A, Seuntjens P, Mallants D, Kim D J, Jacques D, Hubrechts L, Gonzalez C, Feyen J, Diels J, Deckers J. Overview of inert tracer experiments in key belgian soil types: relation between transport and soil morphological and hydraulic properties. Water Resources Research, 2001, 37(12): 2873–2888

[15] Padilla I Y, Yeh T C J, Conklin M H. The effect of water content on solute transport in unsaturated porous media. Water Resources Research, 1999, 35(11): 3303–3313

[16] Oliver Y M, Smettem K R J. Parameterisation of physically based solute transport models in sandy soils. Australian Journal of Soil Research, 2003, 41(4): 771–788

[17] Comegna V, Coppola A, Sommella A. Effectiveness of equilibrium and physical non-equilibrium approaches for interpreting solute transport through undisturbed soil columns. Journal of Contaminant Hydrology, 2001, 50(1–2): 121–138

[18] Maraqa M A. Prediction of mass-transfer coeffificient for solute transport in porous media. Journal of Contaminant Hydrology, 2001, 50(1–2): 1–19

[19] Hu H, Mao X, Barry D A, Liu C, Li P. Modeling reactive transport of reclaimed water through large soil columns with different low-permeability layers. Hydrogeology Journal, 2015, 23(2): 351–364

[20] Kartha S A, Srivastava R. Effect of immobile water content on contaminant transport in unsaturated zone. Journal of Hydro-environment Research, 2008, 1(3–4): 206–215

[21] Feehley C E, Zheng C, Molz F J. A dual-domain mass transfer approach for modeling solute transport in heterogeneous aquifers: application to the Macrodispersion Experiment (MADE) site. Water Resources Research, 2000, 36(9): 2501–2515

[22] FOCUS. FOCUS groundwater scenarios in the EU review of active substances. Report of the FOCUS Groundwater Scenarios Workgroup, 2000, EC Document Reference Sanco/321/2000

[23] Guan J, Molz F J, Zhou Q, Liu H H, Zheng C. Behavior of the mass transfer coefficient during the MADE-2 experiment: new insights. Water Resources Research, 2008, 440(2): 187–194

Acknowledgement

This study was funded by Projects of the National Natural Science Foundation of China (51379207, 51321001).

Compliance with ethics guidelines

Haizhu Hu and Xiaomin Mao declare that they have no conflict of interest or financial conflicts to disclose.

This article does not contain any studies with human or animal subjects performed by any of the authors.

RIGHTS & PERMISSIONS

The Author(s) 2016. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)