Sediment and interstitial water

The sediment surface separates a mixture of solid sediment and interstitial water from the overlying water. Growth of the sediment results from accumulation of solid particles and inclusion of water in the pore space between the particles. The rates of sediment deposition vary from a few millimeters per 1000 years in the pelagic ocean up to centimeters per year in lakes and coastal areas. The resulting flux density of solid particles to the sediment surface is normally in the range 0.006 to 6 kg/m per year (Lerman, 1979). The corresponding flux density of materials dissolved in the trapped water is 10 to 10 kg/m per year. Chemical species may also be transported across the sediment surface by other transport processes. The main processes are (Lerman, 1979) ... 

Experiments examined a chlorocatechol-contaminated sediment, and interstitial water prepared from it. These showed that the concentrations of total 3,4,5-tri- and tetrachloro-catechols (i.e., including the fraction that is released only after alkaline extraction) were apparently unaltered during prolonged incubation even after addition of cnltnres with established dechlorinating capability for the soluble chlorocatechols (Allard et al. 1994). 

Fig. 6.5.4. Vertical profiles of LAS in sediment and interstitial waters from three stations situated at different distances from the non-treated wastewater effluent point (A 12 km B 0.1 km and C 3 km (taken from Ref. [34])).

From the foregoing discussion, it will be appreciated that sediments constitute the final natural compartment for reception of LAS that have not been degraded. The vertical profiles of the concentrations of the LAS homologues in the sediment and interstitial water found for three sampling stations are shown in Fig. 6.5.4. There is a pronounced decrease in LAS concentration with depth, particularly in the first few centimetres, which may be related to greater discharges of effluent into... 

Kolodny, Y. and Kaplan, I.R., 1973. Deposition of uranium in the sediment and interstitial water of an anoxic fjord. Proceedings of the International Symposium on Hydrogeochemistry and Biogeochemistry, Tokyo. The Clarke Company, Washington, DC. 

Lindberg, S.E. and Harris, R.C., 1974. Mercury-organic matter association in estuarine sediments and interstitial water. Environ. Sci. Tech., 8 459—462. 

During the burial of seawater trapped in sediments, interaction of sediments and interstitial water, diffusion of dissolved species in interstitial water and advection of interstitial water occur, causing the variation in chemical composition of interstitial water. 

Table II. ESG assessment of stations based on sediment and interstitial water concentrations of 23 compounds...

One aspect to be addressed in order to obtain a realistic vision of the toxicity of these kinds of compounds is their environmental behaviour. Surfactants tend to be adsorbed on particulate matter and thus subsequently to sediment. Consequently, the highest surfactant concentrations are found in sediments, although their distribution is dependent on the partitioning equilibrium between the substrate and interstitial water. This results in two possible routes for uptake (bioaccumulation) and effect. The relative importance of each of these routes depends on the special habits of each benthic organism. 

A. Metaxatos and L. Ignatiades, Seasonality of algal pigments in the sea water and interstitial water/sediment system of an Eastern Mediterranean coastal area. list. Coast. Shelf Sci. 55... 

Total carbon and nitrogen were analyzed for the core sediments, the interstitial waters, and the peptized aqueous solutions the results are given in Table VIII. The ratios of Total C/Total N of the bulk composition, interstitial waters of the core sediments, and the average ratios of the peptized aqueous solutions are also summarized in Table VIII. 

J. M. and Boothman, W.S. (1996) Predicting the toxicity of metal-spiked laboratory sediments using acid-volatile sulfide and interstitial water normalizations, Environmental Toxicology and Chemistry 15, 2067-2079. 

Berry, W.J., Hansen, D.J., Boothman, W.S., Mahoney, J.D., Robson, D.L., DiToro, D.M., Shipley, B.P., Rodgers, B. and Corbin, J.M. (1996) Predicting the toxicity of metal-spiked laboratory sediments using acid-volatile sulfide and interstitial water normalizations. Environ. Toxicol. Chem., 15, 2067-2079. 

Mg-inhibition. Even if sediments or interstitial waters are at or near saturation with phosphate, there are still impediments to CFA crystallization. One of the most significant is the role of Mg-inhibition. Martens and Harris (1970) demonstrated in the laboratory that when phosphate and fluorine are added to a solution with a composition similar to that of ocean water in Mg VCa ratio, apatite does not crystallize. Instead, a Ca-phosphate gel precipitates with a Ca/P ratio of 1.35 compared to the ratio of 1.67 found in apatite. In their experiments, the gel was kept in the proxy seawater solution for 8 months with no appearance of apatite. However, when the gel was placed in a Mg-free solution, apatite quickly formed. Mg-inhibition results from the smaller Mg ion replacing Ca in the apatite structure, the resultant lattice distortion prevents effective crystal growth (Martens and Harris 1970). Later work by Gulbrandsen et al. (1984) showed that given enough time, in their experimentation seven years, apatite would indeed crystallize from the gel despite the Mg in solution. 

Figure 1 Processes affecting the transport and biogeochemistry of metal pollutants in estuaries and shelf seas. FBI = fresh water-brackish water interface. Metal compartments are designated. Md, dissolved Mp, suspended particulate Mg, sediment M, interstitial water Mp, biogenic particulate.

Fig. 2. Sulfur isotopes of protokerogens and interstitial waters sulfate Solar Lake (Sinai, Egypt). The sediment core of 1 m was extensively studied and reported in Aizenshtat et al. (1983) and Stoler (1981). S Sorg of protokerogens and S Ssuifate from interstitial waters are plotted versus depth.

The redistribution and availability of mercury in the aquatic environment is directly affected by the role suspended and bottom sediments play in the adsorption-desorption process. Sorption phenomena are affected by a variety of bio-geochemical factors including, but not limited to, mercury speciation, associated ionic concentrations, oxygen concentrations, H2S availability, the pH and Eh of the bulk and interstitial waters, bacterial activity, chloride concentrations and sediment type and size. 

Diffusion of dissolved species in interstitial water in sediments cause mass transport between seawater and interstitial water (Berner 1971, 1980 Lasaga and Holland 1976). 

The second method is the flow-coulometry and can be applied to orthophosphates with concentrations of 5x10 1x10 M contained in the interstitial water in sediments. The advantage of this method is that only small amounts of sample ( 100 p.1) are needed and the analytical results are entirely free from interference due to silicate ions. 

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