The Prediction of Partial Anaerobiosis in Saturated Soil: A Transient Moving Boundary Problem

Abstract

AbstractPast models of partial anaerobiosis in saturated aggregates or thin layers of sediment have assumed steady‐state conditions. In this paper, the transient case in one dimension is described. A numerical boundary‐tracking technique was derived to solve the transient case, and a “quasi‐steady‐state” approximate solution was presented. The numerical method yielded accurate results for two test problems, and was shown to converge as the computational mesh was refined. A dimensionless transient problem was solved and the transient numerical solution and a “quasi‐steady‐state” approximation yielded similar results for aerobic/anaerobic boundary velocities < 7 × 10−3 m d−1. This boundary velocity is much greater than those noted in the literature. The results demonstrate that the quasi‐steady‐state approximation is an acceptable description of aerobic/anaerobic boundary movement and oxygen consumption rates under most soil conditions.