Pore Water Composition

Postma D (1981) Formation of siderite and vivianite and the pore-water composition of a recent bog sediment in Denmark. Chem Geol 31 225-244... 

Rai, D., Mattigod, S. V., Eary, L. E. Ainsworth, C. C. 1988. Fundamental approach for prediction pore-water composition in fossil fuel combustion wastes. In McCarthy, G. J., Glassf.r, F. P., Roy, D. M. Hemmings, R. T. (eds) Fly Ash and Coal Conversion Byproducts Characterization, Utilization and Disposal (Symposium Proceedings VI13). Materials Research Society, Pittsburg, PA, 317-324. 

Rai, D., Mattigod, S. V., Eary, L. E. Ainsworth, C. C. 1988. Fundamental approach for predicting pore-water composition in fossil fuel combustion wastes. Materials Research Society Symposium Proceedings, 113, 317-324. 

In Chapter 6, we discussed observations of marine pore water compositions in carbonate sediments that indicated that these waters usually come to a dynamic equilibrium with the most soluble carbonate phase present. Even though these waters are supersaturated with respect to other carbonate minerals, it appears that precipitation reactions are usually sufficiently inhibited that major diagenetic... 

Sayles F.L. (1980) The solubility of Ca(X>3 in seawater at 2°C based upon in-situ sampled pore water composition. Mar. Chem. 9, 223-235. 

To assess the environmental bioavailability, mobility and geochemical cycling of trace elements in soil, analyses of soil pore water composition are frequendy more instructive than those from whole soil or soil extracts. The validity of this concept... 

White A. F., Schulz M. J., Davison V., Blum A. E., Stonestrom D. A., and Harden J. W. (2003) Chemical weathering rates of a soil chronosequence on granitic alluvium III. The effects of hydrology, biology, climate on pore water compositions and weathering fluxes. Geochim. Cosmochim. Acta (in press). 

Abiogenic Reaction Controls on Pore-Water Composition.303... 

In addition to transport and biologically mediated reaction controls on pore-water composition, interstitial solutes are subject to abiogenic reactions with specific solid phases in the sediment (Suess, 1976, 1979 Emerson, 1976 Hartman et al., 1976 Sayles and Manheim, 1975 Martens et al., 1978). The interaction of particular solid phases with pore-water compositions can be inferred in part by examining the disequilibrium state of pore water with respect to selected compounds likely to be present. 

In summary, equilibrium calculations based on pore-water composition indicate that Fe carbonate or phosphate are unlikely to form below the top few centimeters of sediment and that siderite formation is unlikely generally. Undersaturations by a factor of A, p/IAP —100 are found. The presence of solid-phase sulfide is evidence for the formation of Fe sulfides. However, pore waters are not always saturated with respect to the common Fe-sulfide minerals and under-or supersaturations by a factor of —10 are calculated. These deviations may be due to such problems as organic complexing or cumulative analytical and sampling errors, but the possibility that other phases are influencing Fe concentrations cannot be excluded on the basis of these data. 

At least the upper 10 to 30 cm of the core length obtained with either tool is usually adulterated in that it is not appropriate for pore water analysis. The multicorer, high-momentum gravity corer, or at least the box corer should be employed in a parallel procedure to ensure that this layer will also be included as part of the sample. It should not be overlooked that, especially in the deep sea, sampling with two different tools at the same site might imply a distance of several 100 m on the ocean floor. From this deviation considerable differences in pore water composition, and in some of the biogeochemical reactions close to sediment surface, are likely to result. Hence the specification as to same site must be acknowledged with caution. 

The presence of negative spikes in the chloride distribution suggests that the distribution of gas hydrate in marine sediments is highly heterogeneous. Whereas some observations reveal association of hydrate with coarse, high porosity horizons (Clennell et al. 1999), the factors controlling distribution of gas hydrate are not fully understood. Nevertheless, the question remains as to whether the patchy distribution of these deposits can be adequately mapped with pore water analyses. Limitations on how much pore water can be extracted from a section of the core, how many core sections can be dedicated to these analyses, and the time needed for each measurement, usually only allow for sparse measurements of the pore water composition. 

De Lange, G.J., and Brumsack, H.-J., 1998. The occurrence of gas hydrates in Eastern Mediterranean mud dome structures as indicated by pore-water composition, in Henriet, J.P., and Mienert, J., eds.. Gas Hydrates Relevance to World Margin Stability and Climate Change, Special Publications, 137 London, Geological Society, pp. 167-175. 

The electrical conductivity of a sediment depends on the soil type, porosity, water content, and pore water composition. Devices to measure conductivity have been combined with a standard electrical cone to give measurements of cone tip resistance, sleeve friction, and friction ratio (ratio of these two). 

In the highly alkaline pore solution of the concrete (pH of between 12.5 and 13.8, depending on the type of cement used) formed during the hydration of cement, a very thin oxide film (the passive film) protects ordinary reinforcing steel from further dissolution. This passive film remains stable as long as the pore water composition remains constant. When sufficient chloride ions... 

As a result of the electrochemical reaction at the electrodes and the associated transport processes, major changes in the pore water composition take place during the treatment. Beneficial, as it favors repassivation of the rebars, is the increase in OH" concentration near the cathode, and up to 2 M have been determined (Tritthart, 1996). The increase in pH is higher when chlorides are present, because part of the current is transported by the chloride ions (Bertolini et al., 1993 a). 

The process of leaching when applied to the measurement of pore-water compositions is essentially very simple. A leaching solution, normally deionized water, is applied to the sample in such a manner that it accesses the pore space within the rock material, mixing with the pore-water or dissolving residual solutes of the pore-water if the sample has been dried first. The leaching solution is then separated from the rock matrix and analysed for the chemical components extracted from the pore-water. 

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