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Time Variance Analysis of Preferential Solute Movement at a Tile‐Drained Field Site
Author(s) -
Lennartz B.,
Michaelsen J.,
Wichtmann W.,
Widmoser P.
Publication year - 1999
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1999.03615995006300010007x
Subject(s) - outflow , soil water , leaching (pedology) , soil science , environmental science , hydrology (agriculture) , dominance (genetics) , chemistry , geology , geotechnical engineering , biochemistry , oceanography , gene
Preferential flow has been identified as an important secondary process to transport through the soil matrix in controlling solute movement in soils. However, it remains unknown to what extent a fast‐transporting flow regime governs solute leaching and whether it persists for various seasons at field scale. For 3 yr, KBr was applied in late autumn to the surface of a tile‐drained field site (0.5 ha in size) and monitored in drain outflow for 5 mo each year. All three seasonal breakthrough curves (BTC) were dominated by an early first concentration maximum and intensive tailing, indicating preferential flow to be a strong intrinsic soil property at the experiment site. A bimodal probability density function (pdf) was adequate to describe the concentration courses of the first 2 yr of investigations. The coefficient of determination was not satisfying when the model was fitted to the BTC of the last season, which was the only one to have a distinct secondary (matrix) peak. The optimized weighting factor combining the two pdfs suggested that preferential transport mechanisms governed the flow process to about 60% during all 3 yr. Simple linear regression analysis among flow rates and solute concentrations showed that both measures increased and decreased simultaneously during the early stages of the first test, which was interpreted as a confirmation of the dominance of preferential flow. The same method, however, revealed that Br ‐ was leached predominantly through the soil matrix during the corresponding observation period of the last season.