Of pore water

Compaction reduces porosity and permeability. As mentioned earlier during the introduction of growth faults. If the expulsion of pore water is prevented, overpressures may develop. 

Upward flow of pore water and dissolved material caused by pressure gradients. 

Toxicity in estuarine sediments—use of Mutatox and Microtox to evalu- 173 ate the acute toxicity and genotoxicity of organic sediments Toxicity tests for the analysis of pore water sediment a comparison of 4 174... 

Fig. 25.1. Mineralogical consequences of mixing the two fluids shown in Table 25.1 at 60 °C in the presence of microcline, muscovite, quartz, and dolomite. Results shown as the volume change for each mineral (precipitation is positive, dissolution negative), expressed per kg of pore water.

Samples of pore water, ground water, surface water and solid tailings were... 

The composition of pore water was similar in reduced and oxidized tailings with low pH (>1.8) and high total dissolved solids ( 300 g/L) at the surface, and neutral pH and lower dissolved solids with depth. In general, pH values were lower and dissolved metal concentrations higher in... 

In 2004, the pH of pore water in the reduced tailings was 4.4 at <10 cm depth, increasing to 7 by 30 cm. Dissolved constituents follow pH, with concentrations of 36,000 ppm S042", 18,000 ppm Fe, and 9,600 ppm Zn at <10 cm depth. These concentrations decrease steadily with depth. Below 30 cm, most metals drop to below detection limits. 

Thermally enhanced extraction is another experimental approach for DNAPL source removal. Commonly know as steam injection, this technique for the recovery of fluids from porous media is not new in that it has been used for enhanced oil recovery in the petroleum industry for decades, but its use in aquifer restoration goes back to the early 1980s. Steam injection heats the solid-phase porous media and causes displacement of the pore water below the water table. As a result of pore water displacement, DNAPL and aqueous-phase chlorinated solvent compounds are dissolved and volatilized. The heat front developed during steam injection is controlled by temperature gradients and heat capacity of the porous media. Pressure gradients and permeability play a less important role. 

A significant amount of seawater is trapped in the open spaces that exist between the particles in marine sediments. This fluid is termed pore water or interstitial water. Marine sediments are the site of many chemical reactions, such as sulfate reduction, as well as mineral precipitation and dissolution. These sedimentary reactions can alter the major ion ratios. As a result, the chemical composition of pore water is usually quite different from that of seawater. The chemistry of marine sediments is the subject of Part 111. 

As continuing sedimentation increases the depth of a sedimentary layer relative to the seafloor, the overlying pressure increases because of the increased weight of the additional particles. The increased pressure leads to particle compaction if the pore waters can escape upward. Under these conditions, sedimentation generates an upward advective flow of pore water. This flow has the potential to transport solutes. 

Movement of pore water in permeable sediments. A solute trying to move from point A to point B oannot pass through the solid sediment particles and, henoe, must travel around them following a tortuous path. 

The results of concentration measurements are presented as vertical profiles similar to those for the water column, with the vertical axis representing increasing depth below the sediment-water interfece. Depth profiles of concentrations can be used to illustrate downcore variations in the chemical composition of pore waters or in the solid particles. Dissolved concentrations are typically reported in units of moles of solute per liter of pore water. Solid concentrations are reported in mass/mass units, such as grams of carbon per 100 grams of dry sediment (%C) or mg of manganese per kg of dry sediment (ppm Mn). 

The effect of pore-water advection on solute concentrations is given by... 

When sediment settles onto the seafloor, a considerable amount of sediment is trapped between the grains. As discussed in Chapter 12.2.2, pelagic sediments can initially have equal parts of pore water mixed with the solids. As burial progresses, compaction causes the upward vertical advection of pore water, thereby reducing the water content of the... 

Figure 2.13 Effect of mixing of pore water by tubificid worms on profiles of P concentration in submerged soil calculated with Equations (2.37) and (2.40). Numbers on curves are densities of tubificids...

In the marine environment oxygen and hydrogen isotope compositions of pore waters may be inherited from ocean water or inflnenced by diagenetic reactions in the sediment or nnderlying basement. Knowledge of the chemical composition of sedimentary pore waters has increased considerably since the beginning of the Deep-Sea-Drilling-Project. From numerous drill sites, similar depth-dependent trends in the isotopic composition have been observed. 

Ku TCW, Walter LM, Coleman ML, Blake RE, Martini AM (1999) Coupling between sulfur recycling and syndepositional carbonate dissolution evidence from oxygen and sulfur isotope composition of pore water sulfate, South Florida Platform, USA, Geochim Cosmochim Acta 63 2529-2546... 

Wortmann UG, Chemyavsky B, Bemasconi SM, Bmnner B, Bottcher ME, Swart PK (2007) Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (OOP Site 1130). Geochim Cosmochim Acta 71 4221 232... 

Similarly, in plastic concrete, the presence of dissolved calcium, sodium, potassium and sulfate ions lowers slightly the freezing point of pore water, which begins to crystallize as ice at a concrete temperature of about -2° C (28°F) [110]. The addition of the proper combination of salts such as those contained in antifreeze admixtures can further reduce the temperature at which ice formation begins. 

Electrokinetic remediation is limited by the type of contaminant, heterogeneities or anomalies in the soil, extreme pHs, pore water chemistry, lack of pore water, contaminant and noncontaminant ion concentrations, metals precipitation, and reduction-oxidation changes induced by the process electrode reactions. It may be difficult to estimate the time that will be required to remediate a site using this technology. Laboratory treatability testing may provide a false indication of the applicability of electrokinetic remediation at a specific site. Further research is required to determine the technology s limitations and ramifications. 

Quartz is one of the most common minerals in the sedimentary rocks typically associated with coal. A relatively inert mineral, quartz does not significantly affect the acid-alkali balance of pore waters, and to that extent it is environmentally neutral . On the other hand, quartz is the principal agent of silicosis, which is one of the most severe respiratory health problems associated with coal mining. 

Trussed, S. Batchelor, B. 1996. Chemical characterization of pore water of a solidified hazardous waste. In Gilliam, T. M. Wiles, C, C. (eds) Stabilization/Solidification of Hazardous, Radioactive and Mixed Wastes. ASTM,... 

Many cements used today are composites of Portland cement and industrial waste materials that can enter into the hydration reactions and contribute to the strength of the hardened product. These substances include pulverized fuel ash (PFA) from burning of pulverized coal in thermal power stations, crushed blast-furnace slag (Section 17.7), and natural or artificial pozzolanas—that is, volcanic ash and similar finely particulate siliceous or aluminosilicate materials that can react with the Ca(OH)2 in Portland cement to form hydrated calcium silicates and aluminates. As noted earlier, the solubility of Ca(OH)2 is such that the pH of pore water in Portland cements will be about 12.7, at which the Si-O-Si or Si-O-Al links in the solid pozzolanas will be attacked slowly by OH- to form discrete silicate and aluminate ions and thence hydrated calcium silicate or aluminate gels. 

Little Rock Lake. Net IAG in LRL takes place primarily in or near the sediment. It can be evaluated by measurements of pore-water chemistry, comparison of hypolimnetic and epilimnetic chemistry, and calculation of ion budgets. An example of each approach follows. 

Numerous measurements of pore-water chemistry have been made in LRL throughout the experiment (4, 17, 59). Typical vertical pore-water profiles (Figure 6) indicate that the sediments are acting as sinks for sulfate... 

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