Parameterizing the Leaching Surface by Combining Curve-Fitting for Solute Breakthrough and for Spatial Solute Distribution

E Bloem,G H De Rooij,M De Gee

doi:10.1007/s11242-011-9927-2

E Bloem, G H De Rooij + Show 1 more

Open Access

https://doi.org/10.1007/s11242-011-9927-2

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Abstract

Multi-compartment samplers (MCSs) measure unsaturated solute transport in space and time at a given depth. Sorting the breakthrough curves (BTCs) for individual compartments in descending order of total solute amount and plotting in 3D produces the leaching surface. The leaching surface is a useful tool to organize, present, and analyze MCS data. We present a novel method to quantitatively characterize leaching surfaces. We fitted a mean pore-water velocity and a dispersion coefficient to each BTC, and then approximated their values by functions of the rank order of the BTCs. By combining the parameters of these functions with those of the Beta distribution fitted to the spatial distribution of solutes, we described an entire leaching surface by four to eight parameters. This direct characterization method allows trends to be subtracted from the observations, and incorporates the effects of local heterogeneity. The parametric fit creates the possibility to quantify concisely the leaching behavior of a soil in a given climate under given land use, and eases the quantitative comparison of spatio-temporal leaching behavior in different soils and climates.

Highlights

Solute transport in soils is strongly affected by soil heterogeneity, fingered flow and macropore flow
Water and solute are collected in a single container covering the entire bottom of the column, and the measurements result in a breakthrough curve (BTC) (Jury and Roth 1990)
A multi-compartment sampler (MCS) with sample collection area A (L2) has its sampler cells arranged in a rectangular grid of n × n cells with positions (xi, y j ), where xi and y j (L) are horizontal cartesian coordinates of the centers of n2 individual cells identified by the counters i, j {1, . . . , n}

Summary

Introduction

Solute transport in soils is strongly affected by soil heterogeneity, fingered flow and macropore flow. While dye tracers provide information about spatial spreading, the significant adsorption make these tracers less suited to determine the travel times of water (Kasteel et al 2002). Water and solute are collected in a single container covering the entire bottom of the column, and the measurements result in a breakthrough curve (BTC) (Jury and Roth 1990). These single column experiments lack spatial information and the BTC essentially describes one-dimensional solute transport. Field experiments with singlecell sample collectors give a single (spatially averaged) BTC, and only give information about solute transport in one direction

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