Managing soil biophysical properties for environmental protection

The aim of the paper is to show a possibility of management of soil physical properties for environmental protection. In order to do this a proposal for classification of soil properties into such groups as: physical, chemical, biological, physicochemical, biochemical, and biophysical has been presented. A special emphasis was placed on the physical and biophysical properties. The physical properties were subdivided into capacity and intensity, parameters. The capacity parameters cannot be used for the definition of any soil or site specific process since they only define, e.g. the amount of soil mass per volume as the bulk density, but not the arrangement of the mass in the volume. Biophysical soil properties are related to the links between physical and biological fluxes. These fluxes are the consequence of gradients caused by biological sources/sinks and by the transport parameters (conductivity, permeability, diffusivity). In addition, it is also necessary to consider the various phases existing in the soil. Thus, in the gas phase, the biophysical fluxes concern CH4, CO2, O-2, N-2, N2O, etc. They are described by the Fick's law, in which the driving force of the flux is the concentration change in space and time (deltaC/deltax, t) and by the Darcy's law, where the driving force is the pressure change in space and time (deltap/deltax, t). In the liquid phase, there are such flux phenomena as advection and diffusion, described by Darcy's and Fick's laws with pressure (deltap/deltax, t) and concentration (deltaC/deltax, t) gradients as the driving forces. The biophysical phenomena in the solid phase are related, e.g. migration of organic matter, clay particles; sesquioxides, solubility and re-precipitation of minerals, etc. A special group of biophysical phenomena is related to the heat transfer driven by the temperature gradient variable in time (deltaT/deltax, t) and described by the Fourier's law. The biophysical soil properties are important from the environmental point of view, as they are decisive for absorption/emission of oxygen, carbon dioxide, methane, nitrous oxide, NOx, etc. in the soil. Biophysical processes are also essential for functioning of a soil as a biofilter for solids, liquids, and gases. A general example of the role of soil biophysical processes in determination of efficiency of methane oxidation in soil layers, usually, covering re-cultivated municipal landfills, is presented. The example shows a great potential for management of these properties for the protection of the environment. (C) 2002 Elsevier Science B.V. All rights reserved.