Flow regime effects on reactive and non-reactive solute transport

Lennartz, Bernd; Haria, Atul H.; Johnson, Andrew C.. 2008 Flow regime effects on reactive and non-reactive solute transport. Soil and Sediment Contamination, 17. 29-40.

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The lower boundary maintained throughout leaching experiments in column and lysimeter studies influences the transport behavior of solutes. In this study we wanted to determine the effects of different flux regimes and soil organic matter treatments on reactive (pesticide) and non-reactive (bromide) solute movement in lysimeters. Four large soil monoliths, collected from the same experimental site but differing in the organic carbon content by an added manure layer, were subjected to two consecutive leaching tests. Unsaturated steady-state flow with a unit hydraulic gradient was established in Test 1 by applying a constant negative pressure at the base of the lysimeter while during Test 2 atmospheric pressure was maintained (zero-tension). Although less herbicide (isoproturon) was leached from the soil with added manure, the flux regime, as controlled by the lower boundary, dominated the adsorption and the degradation coefficients. The lower moisture content of Test 1 enhanced isoproturon binding, whilst chemical degradation was more effective under the increased but non-uniform soil water content of Test 2. This study demonstrates how solute leaching studies using zero-tension lysimeters do not represent unsaturated in-field processes; the physicochemical processes occurring in unsaturated field soils are only adequately reflected in leaching tests when a constant negative soil water pressure head is maintained throughout the soil sample.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Water > WA02 Quantifying processes that link water quality and quantity, biota and physical environment > WA02.2 Hydrochemical and sediment processes
UKCEH and CEH Sections/Science Areas: Acreman
Additional Keywords: Zero-tension lysimeter, soil water regime, pesticide, bromide, adsorption
NORA Subject Terms: Agriculture and Soil Science
Date made live: 14 Jan 2008 15:20 +0 (UTC)

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