Soil pore structure

Cass, A. and M. E. Sumner. 1982. Soil pore structural stability and irrigation water quality I-Empirical sodium stability model. Soil Sci. Soc. Am. J. 46 503-506. 

McBratney, A.B., andC.J. Moran. 1993. Soil pore structure modeling using fuzzy random pseudofractal sets. p. 495-506. In A.J. Ringrose-Voase and G. Humphreys (ed.) Studies in management and genesis. Proc. 9th Int. Work. Meet. Soil Micromorphol., Townsville, Australia. July 1992. Elsevier, Amsterdam. 

Moran, C.J., and A.B. McBratney. 1997. A two-dimensional fuzzy random model of soil pore structure. Math. Geol. 29 755-777. 

Gas generated in the soil pore structure by processes such as biodegradation of organic material or chemical reactions, etc. Landfill gas is a specific type of ground gas... 

Subsurface formations can be divided into the overburden (unconsolidated) and bedrock according to its solidarity. The upper subsurface can be further divided into the unsaturated zone and the saturated zone depending on pore structure and moisture saturation. The saturated zone is the zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric. The water table is at the top of a saturated zone in an unconfined aquifer. The unsaturated zone is the zone between the land surface and the water table, and is also called the zone of aeration or the vadose zone. The pore spaces contain water at less than atmospheric pressure, air, and other gases. This zone is unsaturated except during periods of heavy infiltration. 

Materials, such as strong acids, strong bases, biocides, or soils heavily contaminated with solvents, would interfere with this technology. Tight clays have the tendency to slow down the propagation of the bacteria due to tight soil structures. With certain salts, the soil pores can be kept open to allow the bacteria access to the contaminants. All information is from the vendor and has not been independently verified. 

Chemical heterogeneities present in soils, sediments, and aquifers undoubtedly have an effect on rates of pollutant degradation. Other sources of surface catalysis not discussed here include Bronsted acidity of surface sites, that become apparent as surfaces become dehydrated (El-Amamy and Mill, 1984). Surface and pore structure may play a role in the catalysis of phosmet hydrolysis by montmorillonite (Sanchez-Camazano and Sanchez-Martin, 1983) and in the catalysis of ethyl acetate hydrolysis by zeolites (Nam-ba et al., 1981). 

Figure 2. Soil water and internal pore structure...

Models that are used to predict transport of chemicals in soil can be grouped into two main categories those based on an assumed or empirical distribution of pore water velocities, and those derived from a particular geometric representation of the pore space. Velocity-based models are currently the most widely used predictive tools. However, they are unsatisfactory because their parameters generally cannot be measured independently and often depend upon the scale at which the transport experiment is conducted. The focus of this chapter is on pore geometry models for chemical transport. These models are not widely used today. However, recent advances in the characterization of complex pore structures means that they could provide an alternative to velocity based-models in the future. They are particularly attractive because their input parameters can be estimated from independent measurements of pore characteristics. They may also provide a method of inversely estimating pore characteristics from solute transport experiments. 

Scott, G J.T., R. Webster, and S. Nortcliff. 1988a. The topology of pore structure in cracking clay soil. 

For pesticides to leach to groundwater, it may be necessary for preferential flow through macropores to dominate the sorption processes that control pesticide leaching to groundwater. Several studies have demonstrated that large continuous macropores exist in soil and provide pathways for rapid movement of water solutes. Increased permeability, percolation, and solute transport can result from increased porosity, especially in no-tillage systems where pore structure is still intact at the soil surface (70). Plant roots are important in creation and stabilization of soil macropores (71). 

A study of numerical modeling of rutting in flexible pavement foundations under cyclic loading was reported by Huang Yu et al., 2001. On the basis of a coupled dynamic soil-pore water system theory a visco-elastic dynamic model has been developed to predict the non-linear response of pavement structure. 

Extracellular phosphohydrolases are proteins. As a general rule, proteins have a strong affinity for solid surfaces. If extended to phosphohydrolases, this phenomenon has two consequences from an ecological point of view. First, phosphohydrolases can be adsorbed, which restricts their mobility by diffusion in the soil pore network and reduces the volume of soil surrounding the producing organism where hydrolysis of Penz can occur. Secondly, adsorption can either modify the conformation of the whole proteic structure (Quiquampotx and Rat-cliffe, 1992 Servagent-Noinville et al., 2000) or lead to an unfavourable orientation of its catalytic site relative to the surface of adsorption (Baron et al., 1999). 

Adsorption It refers to the movement of soluble inorganic phosphorus from soil pore water to soil mineral surfaces, where it accumulates without penetrating the structure (Figure 9.16). Phosphorus adsorption capacity of soil increases with clay content or minerals. Adsorbed phosphorus maintains equilibrium with phosphorus in soil pore water. 

Conceptually, biotransformation of contaminants in soils appears to be influenced by at least three interacting levels of complexity (a) the heterogeneous soil pore network, (b) the abiotic environmental conditions, and (c) the network of cataboli-cally interacting microorganisms responding to their environment. Thus, understanding of the interplay of structure and function of this complex (heterogeneous... 

This investigation of the pore structure details allows one to propose a possible mechanism for the C and N sequestration and pesticides retention in allophanic soils. The large specific surface area is the signature of small pore sizes. Associated to the fractal... 

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