Pore water analysis

Trace metal concentrations in intertidal sediment depth profiles will no doubt continue to provide useful historic records of pollution in the future. In particular, dated profiles that take into account sediment characteristics and diagenetic processes (where appropriate) are of value. Future studies will perhaps be more process-oriented, e.g. by combining pore-water analysis with solid phase data and through a detailed investigation of the nature and significance of the organic matter present. 

Sediment quality assessment is part of the sustainable sediment management of the European Sediment Research Network Sediment (SedNet, 2003). In recent years, a paradigm shift has taken place to give priority to biological data (Den Besten et al., 2003). Chemical sediment analysis for monitoring studies is usually combined with biological investigations and could be supported by pore water analysis ... 

Table VII. Pore water Analysis of Stored-Core FR5A... 

Fig. 3.13 Application of a high-momentum gravity corer (Meischner and Rumohr 1974) to obtain samples from marine sediments. The device can also be stationed on smaller vessels and is suited to extract almost unperturbed cores measuring 1 m in length to be applied in pore water analysis.

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. 

This work was carried out in the framework of the CCE-CEA Project number FI 2W CT9-0115 (1992-1996). The preliminary pore-water analysis and modelling have been perform in collaboration with Drs M. Mazurek H. N. Waber (Rock-Water Interaction Group, University of Berne, Switzerland). The OM analysis has been realised by Professor Ambles (Labo de Chimie XII, Universite de Poitiers, France). The authors finally acknowledge their colleagues Drs S. Bassot, C. Beaucaire and H. Pitsch for fruitful discussions on water-rock interactions, and the referees and editors for their valuable comments. 

Ugo P, Moretto LM, Rudello D, Bitriel E, Chevalet J (2001) Trace iron determination by cyclic and multiple square-wave voltammetry at nafion coated electrodes. Application to pore-water analysis. Electroanalysis 13 661-668... 

Components in the invading water-based filtrate and in the formation waters may react to form insoluble precipitates which can block the pores and give rise to skin damage. The scale can be formed by interaction of calcium-based brines with carbon dioxide or sulfate ions in the formation water. Alternatively sulfate ions in the invading fluid may react with calcium or barium ions in the formation water. Analysis of the formation water can identify whether such a problem may arise. 

Shipboard analysis for the sampling of trace metals in seawater has been discussed by Schuessler and Kremling [2] and Dunn et al. [3]. Teasdale et al. have reviewed methods for collection of sediment pore-waters using in situ dialysis samples [4]. Bufflap and Allen [5] compared centrifugation, squeezing, vacuum filtration, and dialysis methods for sediment pore-water sampling. 

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... 

External precision is the ability to demonstrate analytical repeatability with multiple preparations and analyses of a material over a long period of time. The MC-ICP-MS techniques and the more widespread TIMS methods either demonstrate or claim external precisions in the range 0.5 to 1.0%o (2ct). The stated precision for most TIMS methods is estimated from the reproducibility of the L-SVEC standard. In many cases the analysis of individual samples prepared multiple times yields precisions poorer than this estimate. This is in part due to the heterogeneity of natural samples and in part due to effects introduced during preparation and analysis that are not experienced by the standard. Zhang et al. (1998) cite reproducibility of the L-SVEC standard of <1.0%o (2ct), but their duplicate measurements of individual pore water samples vary from 0.1 %o to 6.1 %o (mean 2.3%o all 2cj). Later studies using refined TIMS procedures appear to achieve superior replicate precision (e.g., 0.4%o to 1. l%o for multiple replicates in Chan et al. 2002c). 

Another possible solution to the problem of analyzing multiple-layered membrane composites is a newly developed method using NMR spin-lattice relaxation measurements (Glaves 1989). In this method, which allows a wide range of pore sizes to be studied (from less than 1 nm to greater than 10 microns), the moisture content of the composite membrane is controlled so that the fine pores in the membrane film of a two-layered composite are saturated with water, but only a small quantity of adsorbed water is present in the large pores of the support. It has been found that the spin-lattice relaxation decay time of a fluid (such as water) in a pore is shorter than that for the same fluid in the bulk. From the relaxation data the pore volume distribution can be calculated. Thus, the NMR spin-lattice relaxation data of a properly prepared membrane composite sample can be used to derive the pore size distribution that conventional pore structure analysis techniques... 

Most of our understanding of the marine chemistry of trace metals rests on research done since 1970. Prior to this, the accuracy of concentration measurements was limited by lack of instrumental sensitivity and contamination problems. The latter is a consequence of the ubiquitous presence of metal in the hulls of research vessels, paint, hydrowires, sampling bottles, and laboratories. To surmount these problems, ultra-clean sampling and analysis techniques have been developed. New methods such as anodic stripping voltammetry are providing a means by which concentration measurements can be made directly in seawater and pore waters. Most other methods require the laborious isolation of the trace metals from the sample prior to analysis to eliminate interferences caused by the highly concentrated major ions. 

Of special interest in recent years has been the analysis of natural gas hydrates that form in marine sediments and polar rocks when saline pore waters are saturated with gas at high pressure and low temperature. Large and 5D-variations of hydrate bound methane, summarized by Kvenvolden (1995) and Milkov (2005), suggest that gas hydrates represent complex mixtures of gases of both microbial and thermogenic origin. The proportions of both gas types can vary significantly even between proximal sites. 

Two different approaches have been taken by researchers to determine the secondary mineralogy of CCBs (1) direct observation, which is accomplished via analysis of weathered ash materials, and (2) prediction, based on chemical equilibrium solubility calculations for ash pore-waters and/or experimental ash leachate or extractant solutions. Because the secondary phases are typically present in very low abundance, their characterization by direct analysis is difficult. On the other hand, predictions based on chemical equilibrium modelling or laboratory leaching experiments may not be reliable indicators of element leachability or accurately indicate the secondary phases that will form under field conditions (Eighmy et al. 1994 Janssen-Jurkovicova et al. 1994). 

It is important to note two things in this analysis first, the reactions which govern silicate phase equilibria occur in a system closed to large-scale chemical migration. This corresponds to a pore-water sediment system of local equilibrium. Second, the most striking mineralogical change—the crystallization of feldspar—is, in fact, the result of the instability of another phase, montmorillonite. The use of... 

Solid-phase sediment digestions were analyzed in triplicate, with one duplicate digestion and a spike recovery or analysis of reference material every 10 samples. Coefficients of variation (C.V.) for triplicates fell within 0.5-11.5% [n = 60, mean C.V. = 3.6% 2.4% (std)], and spike recoveries were within 90-103% [n = 3, mean = 96% 7%]. Eight replicates of standard reference material [National Institute of Standards and Technology (NIST) Tennessee River sediment, Catalog No. 8406] were within 10% (0.053 0.004 xg/g, C.V = 7.2%) of the recommended value of 0.06 xg/g. A standard reference for Hg in natural water was not available. Typical duplicates of small-volume pore waters (<30 mL) had an average C.V of 30.8% 22% (n = 30). 

Lake sediments TT pore water Organic analysis B (Guzzella et al., 1996)... 

TT pore water Heavy metal and organic analysis I (Cataldo et al., 2001)... 

Chapman, P.M., Wang, F., Germano, J.D. and Batley, G. (2002) Pore water testing and analysis the good, the bad, and the ugly, Marine Pollution Bulletin 44, 3 59-366. 

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