Sediment seawater interface

Recently, a novel microbial fuel cell harvesting energy from the marine sediment—seawater interface has been reported. Also, a novel photosynthetic biofuel cell that is a hybrid between a microbial and enzymatic biofuel cell has been reported for the very first time. More recently, reports of an unconventional biomass-fueled ceramic fuel cell can also be found in the literature. A new concept of Gastrobots —hybrid robots that utilize operational power derived from microbial fuel cells—has been introduced. Finally, the generation of electrical power by direct oxidation of glucose was demonstrated in mediatorless microbial fuel cells, which produced currents up to 3 fiA/cm at unknown cell voltage. ... 

Pavlou, S.P. Dexter, R.N. (1980) Thermodynamic aspects of equilibrium sorption of persistent organic molecules at the sediment-seawater interface a framework for predicting distribution in the aquatic environment. In Contaminants and Sediments, ed. R.A. Baker, pp. 323-329. Ann Arbor Ann Arbor Sci. Publ. 

The typical effects of the earliest stages of "diagenesis" (involving transformations of organic matter, "aging" of mineral components and formation of new equilibria between solid and dissolved species) have been demonstrated by Salomons (1980) with respect to the behaviour of trace metals at the sediment/seawater interface (Table 3-5). 

Chesselet, R., 1979. Modes of settling and organic input to the sediment seawater interface. Colloque International C.N.R.S. Biogeochimie de la matiere organique a I inter-face eau- ediment marin, Marseille (extended abstract). 

We may think in general of marine or terrestrial wet and dry sites, but microenvironments within these provide unique conditions. Microenvironments in a marine burial site may include anaerobic sediments, aerobic sediments, sediment-seawater interface, and others (19) (Figure 20). Dif-... 

Figure 20. Microenvironments in a marine burial site. Each interface (i.e.y artifact-seawater-atmosphere interface, artifact-sediment-seawater interface, etc.) has specific environmental parameters that dictate a specific type of deterioration. (Reproduced with permission from ref. 9. Copyright 1987...

A more widespread process consists of the hydrogenous formation of clay at the sediment-seawater interface, in deep-sea environments characterized by water depths > 4000 m, insignificant terrigenous supply, and very low sedimentation rate (South Pacific basins. The sediments mostly consist of reddish-brown oozes rich in Fe and Mn oxides (i.e., deep sea red clay ). There iron-rich smectites of the nontronite group may form in significant proportions, probably due to long-term low temperature interactions between (1) metal... 

A monograph Chemistry of Sediment-Seawater Interface of China s Seas , which concerns the marine biogeochemical process, was published in 1997 (Song, 1997a). The monograph contains 7 chapters and the main contents are as follows ... 

An outline of the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea and the feature of surface sediments in China s seas are given in chapter 1. The contents and methods of studying the marine sediment-seawater interface are summarized in chapter 1 and chapter 2. The chemical features of overlying waters of marine sediments are described in chapter 3. 

The diffusion fluxes across the sediment-seawater interface of China s seas are discussed using Pick s Law. Two main conclusions should be paid much attention to (1) In the location of volcanic activities, the diffusion fluxes of elements from sea bottom to water are very high, for instance in the Okinawa Trough the diffusion flux of Cl from sediment to water is as high as 10.24 mmol/(m d). (2) In the coral reef ecosystem of the Nansha Islands, a large number of nutrients such as N, P, and Si are diffused to seawater, so it is apparent that the diffused nutrients are key factors for maintaining the high production of the coral reef ecosystem. 

Phosphorus is not only one of the essential components for the growth and breeding of phytoplankton, but also the fundamental element for marine primary productivity and the food chain. Sediment is one of the important sources of phosphorus in seawater moreover, it is a buffer for the phosphorus in overlying water. Therefore, it is of great significance for the dynamic cycle, the transformation at the sediment-seawater interface, and the subsequent digenesis to study phosphorus and its forms. 

The diffusing fluxes of biogenic elements across sediment-seawater interfaces mainly depend on the diffusion of the concentration difference caused by the concentration gradient near the interfaces. The net diffusing fluxes of biogenic elements across the sediment-water interface in some of China s sea regions can be estimated by the First Fick Law, and the results are listed in Table 1.10. 

Table 1.10. Diffusion fluxes across the sediment-seawater interfaces in China s seas...

In conclusion, the differences in biogenic element diffusing fluxes near sediment-seawater interfaces in different regions are great, and their directions are not all the same. It reflects the differences in their early diagene-... 

Song JM (1997a) Chemistry of Sediment-Seawater Interface of China Sea. China Ocean Press, Beijing, pp.1-222 (in Chinese)... 

Earlier research indicated that many factors affect the contents and distributions of P and Si in sediments as well as P and Si transfer across the sediment seawater interface. Marine sediments are an important source and sink of P and Si in sediments and have more important functions than scientists considered before. Hence, it is necessary to ascertain which factor has the largest impact on the cycling (release and burial) of P and Si in the southern Bohai Sea. In other words, the major factor controlling the interface cycle of P and Si must be determined. 

Ruttenburg KC (1992) Development of a sequential extraction method for different forms of phosphorus in marine sediments. Limnol Oceanol 37(7) 1460-1482 Rysgaard S, Risgaard-Petersen N, Nielsen LP, Revsbech NP (1993) Nitrification and denitrification in lake and estuarine sediments measured by the N dilution technique and isotope pairing. Appl Environ Microbiol 59(7) 2093-2098 Shaked Y, Erel Y, Sukenik A (2002) Phytoplankton-mediated redox cycle of iron in the epilimnion of Lake Kiimeret. Environ Sci Technol 36(3) 460-467 Shukla SS, Syers JKJ, Williams DH (1971) Sorption of inorganic phosphate by lake sediments. Soil Sci Soc Am Proc 35(2) 244-249 Song JM (1997) Chemistry of Sediment-Seawater Interface of China s Seas. China Ocean Press, Beijing, pp. 1-222 (in Chinese)... 

Only 15.5% of biogenic silicate is hydrolyzed during the journey from the surface to the bottom in seawater, thus ca. 84.5% can be deposited on the bottom. The silicate release rate at the sediment-seawater interface is quite a bit lower than its accumulation rate from water to sediment. They are the main reasons for a constantly low silicate concentration in sea water and Si-limitation in phytoplankton primary production. In one... 

Song JM (1997) Chemistry of Sediment-Seawater Interface of the China Seas. 

Table 5.39. Diffusion fluxes of sulfur across sediment-seawater interface in the Nansha coral reef lagoon waters, South China Sea (Song and Li, 1996b)...

Processes (2.115) and (2.116) describe the solid-liquid equilibrium at the oceanic bottom (sediment-seawater interface) with suspended matter in seawater (calcareous organisms). Moreover, similarly the processes of heterogeneous nucleation and droplet formation from CCN as well as in general the solid-water interfacial process are described (Fig. 2.93). Hence, seawater is an excellent solvent for acidic gases such as SO2 (used for flue-gas desulfurization at some coastal site power stations) and atmospheric CO2. The ratio between atmospheric and oceanic (water dissolved) CO2 is described by the Henry equilibrium (2.117 see also Chapter 4.3.2) ... 

Fig. 10. Isothermal logarithmic plots of organic acid concentrations for natural samples. The curves are drawn with slopes of 3/2, which is indicative of metastable equilibrium with respect to reaction (28). Numbers on plot from data of Martens (1990) indicate depths (in cm) below the sediment/seawater interface...

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