Effect of Non-Perfect Correlation of Particle Velocities in Soil Layers with Different Sorption and Decay on Reactive Transport
Abstract
A vertical gradient in chemical and biological properties is prominent in most soils together with an increase in dispersivity with travel distance. The increase in dispersivity indicates that particle velocities are correlated over a spatial scale which is similar to the scale of the transport process. As a consequence, particle velocities are likely to be correlated in soil layers with different sorption and decay parameters. Vanderborght and Vereecken 2007 demonstrated the impact of particle velocity correlations on reactive transport in a layered soil profile with 1-D transport simulations making opposite assumptions about the correlation of particle velocities: either a perfect correlation (stream tube model, STM) or zero correlation (convective dispersive equation, CDE). We extend this analysis to the more realistic case of imperfect velocity correlation. Simulations with a 1-D transfer function model that considers imperfect particle velocity correlations are compared with STM and 1-D CDE simulations. The CDE with soil layer dependent dispersivities and the STM underestimated the simulated leached mass fraction by the non-perfect correlation transfer function model: the STM since it underestimates the dispersion in the first soil layer and the layered CDE since it cannot account for the effect of particle velocity correlations. A 1-D CDE with a uniform dispersivity in the soil profile predicted the highest leached mass fraction since it overestimated the dispersive flux and leached mass fraction through the top layer where the decay rate was assumed to be the highest. The 1-D model simulations were compared with 2-dimensional flow and transport simulations in heterogeneous hydraulic conductivity fields. These simulations were used to validate the procedure to derive the correlation of particle velocity in different soil layers from breakthrough curves (BTCs) of an inert tracer at different depths and to validate predictions of BTCs of reactive substances by the non-perfect correlation transfer function model. Vanderborght, J., and H. Vereecken. 2007. One-Dimensional Modeling of Transport in Soils with Depth Dependent Dispersion, Sorption, and Decay. Vadose Zone J. 6:140-148.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.H54C..02V
- Keywords:
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- 1832 HYDROLOGY / Groundwater transport;
- 1865 HYDROLOGY / Soils