Abstract
This study is for the purpose of clarifying the properties of dissolved oxygen content (DO) in seepage water of open and the closed system percolation and the availability of pressure causing entry pores (pk) that distinguish these DO properties. I used undisturbed soil having opensystem percolation that we had reported about.
In the experiment, DO in seepage water and pressure head were measured at short intervals in the vertical plane, and then, the drain level was controlled by the soil column models. The composition of the soil column models corresponded to the stratified soil (3 layers) of a paddy field that we had observed to be the open system percolation. As a result of this observation, the following information was obtained.
1) In case of the low drain level, both surface soil (positive pressure, Kuroboku soil) and plowsole (negative pressure, Kuroboku soil) became the closed system percolation and DO in this seepage water was about 2 ppm. Subsoil (negative pressure, loam) became the open system percolation and DO of this seepage water rapidly increased to a class of 6 ppm and retained their oxidation state in soil column models. However, in case of the high drain level, all layers became the closed system percolation (positive and negative pressure) and it was observed that every layer's DO in this seepage was about 2 ppm.
2) It was recognized that the increase and decrease of DO in down seepage water was caused by whether the pressure head of subsoil was larger than pk or not.
It follows from the above results that the DO properties of the increase and decrease appeared in seepage water of the open and closed systems and that pk's availability for distinguishing this phenomenon was high.
