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Movement of water and the herbicides atrazine and isoproturon through a large structured clay soil core.

Research output: Contribution to journalJournal article

Published

Journal publication date1995
JournalJournal of Contaminant Hydrology
Journal number3
Volume19
Number of pages24
Pages237-260
Original languageEnglish

Abstract

A large (1.1 m × 0.8 m in diameter) core of strongly cracked clay soil was instrumented with eight suction samplers, ten zero-suction samplers and sixteen pressure transducer tensiometers. Results of three rainfall events labelled with potassium bromide, pentafluorobenzoic acid and 2,6-difluorobenzoic acid indicate rapid bypass flow, matrix advection and mixing of water between the soil macropores and the matrix all occurred. Generally, no sharp distinction was observed between crack flow and matrix advection; water flow was best described by a continuum of flow phenomena. Before rainfall application, the herbicides atrazine and isoproturon were applied to the soil surface at rates typically used in the field (2.475 kg active ingredient/ha). Rapid bypass flow in large cracks, by which some of the solutes were transported with limited contact with the soil, was mainly responsible for redistribution of the herbicides and their movement to depth in short time periods. Over the course of the experiments 0.23 pore volumes of rainfall were applied to the core but only 0.02 pore volumes were recovered by gravity drainage. Less than 1% of the herbicides applied was lost in water draining from the soil core.