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

Soil cores from river marginal wetlands from the Torridge and Severn catchm ents in the UK were collected to study rates of soil denitrification at dif ferent sites and at two stations (levee and backplain depression) at the ri ver margin. Half the cores were sterilized prior to flooding to destroy the denitrifying bacteria. After flooding and equilibration, monitoring the co ncentration 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 d iffusion coefficient of the nitrate ion in the flooded soils. An expression was developed that permitted this diffusion coefficient to be extracted fr om 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 experi ments; this work develops a procedure whereby they may yield useful soil pr ocess information. Copyright (C) 2001 John Wiley & Sons, Ltd.