Pore water definition

EH s that are often encountered in sediment pore waters. Cores from Mono ake (not shown) had extremely alkaline pH s of 9.8 to 10.1. This high a pH definitely has an effect on the bimane reaction. Pore water samples adjusted to pH 8 gave much higher results which were similar to those obtained from the methylene blue and DTNB method (data not shown). Thiosulfate and sulfite were present in micromolar quantities in cores from all habitats. Thiosulfate was highest in the salt pond cores where it occasionally was more abundant than sulfide. While methane thiol, glutathione, and other organic thiols can be detected by the bimane method, they were not abundant (< 10 mM) in the core samples we chose to analyze. 

Field methods for sampling pore water are generally grouped under the general term lysimetry. This definition usually comprises a range of types of samplers (Wolt, 1994) ... 

These redox cells can operate on a number of scales that depend on the length of the diffusion path from the point that the oxidised form becomes reduced to the point where it reduces another sediment constituent. In some pelagic cores these diffusion paths can be observed in linear portions of the pore-water profiles (e.g. Sawlan Murray, 1983). Here the sedimentation rate and the carbon burial rate are sufficiently low, relative to diffusion, to extend the processes of early diagenesis over tens of metres into the sediment. In coastal environments the sedimentation rate and the concentration and reactivity of the organic matter is often high, which results in a much more complex pattern. In this case, the distances between the cells are much shorter, since by definition the adjustment must occur more rapidly. Like laminar and turbulent flow, there may come a point where the flow of electrons downwards is better dispersed through eddies , which in this case are transitory micro-environments with small-scale three dimensional diffusion, rather than more stable... 

For various purposes, the dissolved concentration (or even the free ion activity) in the pore water can be used to explain effects. In those cases available fraction and pore water concentration are equivalent. This is, however, only one of the definitions of bioavailability. Based on the pore water concentration (actual availability) it is possible to explain targets such as the... 

Another problem arising from titration of alkalinity in a pore water sample usually consists in the fact that samples with very small volumes cannot easily be used. Most ocean chemists will be accustomed to the titration of a volume of 100 ml, or at least 10 ml. Under certain circumstances, a pore water sample obtained from a definite depth might contain in total not more than 10 ml, hence, at best, merely 1 ml needs to be sacrificed for the titration of alkalinity. This requires that markedly pointed and thin (thus easily breakable) pH-electrodes are used. These are immersed, together with an electronically controlled micropipette, into a small vial so that a tiny magnetic stirrer bead still has enough room to fit inside as well. 

When we say that concrete is alkaline we mean that it contains microscopic pores with high concentrations of soluble calcium, sodium and potassium oxides. These oxides form hydroxides, which are very alkaline, when water is added. This creates a very alkaline condition (pH 12-13 -see the glossary for a definition of pH). The composition of the pore water and the movement of ions and gases through the pores is very important when analyzing the susceptibility of reinforced concrete structures to corrosion. This more fully discussed in Chapter 3. 

In the present work Gallerkin s method of weighted residuals is used to derive the weak form of the equilibrium equations. Hence, the first step towards finite element discretisation of the governing equations is the definition of shape functions for the domain variables, i.e. displacement, pore water pressure and pore air pressure. Introducing these shape functions into equations 13, 14 and 15 the governing equations are approximated with a certain accuracy. The approximation errors, termed... 

FIG. 13 Average number of hydrogen bonds (for definition see text) as a function of p in five simulations at different levels of hydration in a Vycor pore. Full hues show the number of water-water bonds, long-dashed hnes show the number of bonds between water molecules and Vycor, and short-dashed lines denote the sum of the two. From top to bottom, the frames correspond to a water content of about 96, 74, 55, 37, and 19% of the maximum possible (corresponding to 2600, 2000,1500, 1000, and 500 water molecules in a cylindrical cavity of about 4nm diameter and 7.13 nm length). (From Ref. 24.)... 

Permeability is defined as a measure of a rock s ability to transmit fluids. In addition to a rock s being porous, sedimentary rock can also be permeable. Permeability refers to the property of a rock that allows fluids to flow through its pore network at practical rates under reasonable pressure differentials. The quantitative definition of permeability was first given in an empirical relationship developed by the French hydrologist Henry D Arcy who studied the flow of water through unconsolidated sands [31]. 

By definition groundwater can be found almost anywhere. The ground-water table is defined as the level under which all pores or fractures are water saturated, see Figure 32. 

By definition, the anion-free water is free of salt. When pressure is applied to a clay-brine slurry to force out water (as that described in the experimental section), the solution that flows out of the cell should maintain the same chloride concentration as the brine s if the anion-free water is immobile. Otherwise, the concentration of the chloride decreases. Pressure forces water to flow through the pores with a certain velocity meanwhile, the pore size... 

Fig. 7. Size scale associated with soil mineral particles, organic components, pores and aggregations of mineral and organic components (Baldock 2002). The definitions of pore size have used those developed by IUPAC (micropores < 2 nm, mesopores 2-50 nm and macropores > 50 nm). Alternatively, the pore sizes corresponding to the lower ( /m = - 1500 kPa) and upper ( /m = - 100 kPa) limits of water availability to plants may be used to define the boundaries between the different classes of pore size. /m is soil water metric potential.

We have defined the properties faced by developers of new growing media. Based on these definitions, it is clear that reticulated foam would not be useful for such applications. Even at the finest pore size, virtually no water is retained during this test. If, however, we were to graft hydrophilic polyurethane onto a reticulated foam, the grafted polyurethane increases the amount of water retained in the moisture tension test. If an organic fiber such as peat moss is included in the hydrophilic polyurethane, the effect is even more pronounced. Applications in both hydroponic and soil planting are anticipated from this technology. 

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