Measuring the millimetre-scale oxygen diffusivity in soil using microelectrodes |
| |
| Authors: | C RAPPOLDT |
| |
| Institution: | Department of Theoretical Production Ecology, Agricultural University, P.O. Box 430, 6700 AK Wageningen, The Netherlands |
| |
| Abstract: | The diffusivity of oxygen in soil was measured by periodically changing the gas above a soil core from nitrogen to air and vice versa. The concentration wave was measured as a function of depth with an oxygen electrode. For different Fourier components in the signal, phase shifts were calculated. The diffusivity follows from the increase of the phase shift with depth. Phase shifts are more suitable than signal amplitudes for the derivation of diffusivity. They are also easier to measure and do not require electrode calibration. For a clay soil with an air–filled porosity of about 0.05 m3 m?3 a local diffusivity of 0.9 × 10?9 m2 s?1 was measured. This is several orders of magnitude smaller than macroscopic values for entire core samples of the same soil type. This low value can be explained by the presence of locally water–saturated clay. |
| |
| Keywords: | |
|
|
