A simple method for the determination of ionic diffusion coefficients in flooded soils

Soil cores from river marginal wetlands from the Torridge and Severn catchments in the UK were collected to study rates of soil denitrification at different sites and at two stations (levee and backplain depression) at the river margin. Half the cores were sterilized prior to flooding to destroy the denitrifying bacteria. After flooding and equilibration, monitoring the concentration of amended nitrate in the supernatant of the sterile cores over a period of 7 days provided a simple procedure for the estimation of the diffusion coefficient of the nitrate ion in the flooded soils. An expression was developed that permitted this diffusion coefficient to be extracted from the slope of a plot of supernatant concentration versus (time)(1/2). The values obtained, at 15 degreesC, varied from 2.4 to 6.8 x 10(-10) m(2) s(-1). Sterile cores are usually treated as controls in denitrification experiments; this work develops a procedure whereby they may yield useful soil process information. Copyright (C) 2001 John Wiley & Sons, Ltd.