|Casey, Francis - IOWA STATE UNIVERSITY|
|Horton, Robert - IOWA STATE UNIVERSITY|
Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: July 23, 1996
Publication Date: N/A
Technical Abstract: Determining the preferential flow characteristics of a soil is important because agrichemicals can contaminate groundwater via preferential flow pathways. A model that predicts solute transport due to preferential flow is the mobile/immobile solute transport model, which partitions the total water content into a mobile fraction and an immobile fraction. Recently, an in situ method was proposed for determining two of the model parameters and mass exchange coefficient. The method uses a tension infiltrometer to apply a series of four fluorbenzoate tracers to determine mass exchange coefficient and immobile fraction. The method was used to perform forty-seven experiments along a transect in a ridge-till corn field of loamy soil, mapped as a Nicollet series. The values of immobile fraction ranged from 0.952 to 0.288 with mean 0.618 and standard deviation of 0.148, and the values of mass exchange coefficient ranged from 0.0112 min**-1 to 0.000235 min**-1 with mean 0.00164 min**-1 and standard deviation of 0.00161 min**-1. These field values were similar in magnitude and range to laboratory soil column values reported by others. The values along the transect indicated no obvious spatial trends.