MODELING NONEQUILIBRIUM CONTAMINANT TRANSPORT PROCESSES IN SOILS AND GROUNDWATER

Abstract. Few studies have been carried out that cover the entire transport process of pesticides, from application at the soil surface, through subsurface transport, to contamination of drinking water in esker aquifers. In formerly glaciated areas, such as Scandinavia, many of the most important groundwater resources are situated in glaciofluvial eskers. The purpose of the present study was to model and identify significant processes that govern subsurface transport of pesticides in extensive glaciofluvial and littoral sediments. To simulate the transport processes, we coupled a vadose zone model at the point scale to a regional groundwater flow model. The model was applied to a municipal drinking-water aquifer, contaminated with the pesticide-metabolite BAM (2,6-dichlorobenzoamide). A sensitivity analysis revealed that hydraulic conductivity and infiltration rate accounted for almost half of the model uncertainty. For a ten-meter-deep vadose zone of coarse texture, macropore flow was found to be of minor importance for contaminant transport. The calibrated model was applied to optimize the location of extraction wells for remediation, which were used to verify the predictive modeling. Running a worst-case scenario, the model showed that the establishment of two remediation wells would clean the aquifer in four years, compared to nine years without them. Further development of the model would require additional field measurements to assess the importance of macropore flow in deep, sandy aquifers. We also suggest that future research should focus on characterization of the variability of hydraulic conductivity and its effect on contaminant transport in eskers.

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Exact analytical solutions for contaminant transport in rivers 1. The equilibrium advection-dispersion equation

Journal of Hydrology and Hydromechanics ◽

10.2478/johh-2013-0020 ◽

2013 ◽

Vol 61 (2) ◽

pp. 146-160 ◽

Cited By ~ 30

Author(s):

Martinus Th. van Genuchten ◽

Feike J. Leij ◽

Todd H. Skaggs ◽

Nobuo Toride ◽

Scott A. Bradford ◽

...

Keyword(s):

Surface Water ◽

Dispersion Equation ◽

Contaminant Transport ◽

Analytical Solutions ◽

Decay Chain ◽

Transport Processes ◽

Dispersive Transport ◽

Chain Reactions ◽

Surface Water Hydrology ◽

Advection Dispersion

Abstract Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-water hydrology, are scattered across the literature, and not always well known. In this two-part series we provide a discussion of the advection-dispersion equation and related models for predicting concentration distributions as a function of time and distance, and compile in one place a large number of analytical solutions. In the current part 1 we present a series of one- and multi-dimensional solutions of the standard equilibrium advection-dispersion equation with and without terms accounting for zero-order production and first-order decay. The solutions may prove useful for simplified analyses of contaminant transport in surface water, and for mathematical verification of more comprehensive numerical transport models. Part 2 provides solutions for advective- dispersive transport with mass exchange into dead zones, diffusion in hyporheic zones, and consecutive decay chain reactions.

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