Dynamics of partial anaerobiosis denitrification, and water in soil : experiments and simulation

Abstract

Dynamic interactions between biological respiration and denitrification, and physical transport processes that modify the abiotic soil environment in which bacteria live, were studied through the development of a new type of experimental respirometer system and an explanatory simulation model.The respirometer system enables one to measure simultaneously the distribution of water, oxygen, nitrate, ammonium, and pH as a function of space and time in an unsaturated, artificially made, homogeneous, cylindrical soil aggregate. The coherent data sets that were obtained by this experimental system served to test the explanatory simulation model.The simulation model comprises four submodels: 1) biological respiration and denitrification, 2) water transport including a description to account for hysteresis, 3) solute transport, and 4) gas transport including a new description to simulate the integral soil atmosphere. Besides evaluation of the integral model with the results of the respirometer system, three of the submodels were also separately tested, either by means of experiments (submodel 1 and 2) or by analytical solutions (a special case of submodel 4).It was found that the new respirometer system yields valuable data to test the simulation model, and that the simulation model gives a fair description of the measured data. However, it appears that only the combined study of the results of experiments and simulations will deepen the understanding of the complicated interactions that occur in this soil biological ecosystem.It was the objective of this study to describe the respirometer system, the explanatory simulation model, and the tests that were done to evaluate the integral model and the separate submodels