The Ocean Environment

From ships to submarines to mining the sea floor, certain plastics can survive sea environments, which are considered more hostile than those on earth or in space. For water- 

Plastics have already become vital for operating within the sea, even though comparatively little is yet known about the qualities of the sea (see Fig. 4-30). This frontier s practical opportunities were first developed with submarines, which until the nuclear ones were limited to depths of only a few hundred feet. Many thousands of feet can now be navigated. The crushing pressures below the surface, which increase at a rate of about h psi per foot of depth, make corrosion a major threat to the operation and durability of many materials. For example, the life of uncoated magnesium bolts in contact with steel nuts is less than seventy-two hours, and aluminum buoys will corrode and pit after only eleven months at just four hundred feet. 

Tests on plastics in deep water have been extremely encouraging. Low-carbon steel corroded at a rate one-third greater than in surface waters. Filament-wound reinforced plastic cylinders and PVC buoys retained their strength. PVC washers and the silicone sealing compound used in steel-to-aluminum joints helped prevent corrosion. 

Black twisted nylon and polypropylene ropes used to rig and retrieve test platforms were unaffected. Grappling lines attached to platforms, made of steel wire jacketed with extruded high-density PE, prevented corrosion of the steel. PE is also used to protect submerged telephone cables. Plastic primers such as epoxy are used to prevent antifouling paints from corroding metals. These paints generally use cuprous oxide to prevent the growth of barnacles, but at the same time can be harmful to metal. 

Plastics are used successfully in instruments to determine depth, the velocity of currents, temperature, and as echo sounders. Parts operating to depths of 4,500 m (15,000 ft.) include molded polystyrene rotors, neutrally buoyant polyethylene control vanes, PVC 

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U-SERIES ISOTOPES IN THE OCEAN ENVIRONMENT 2.1. The ocean uranium budget... 

The chemical behavior of U and its daughter nuclides in the ocean environment was extensively studied in the 1960s and 1970s and has been well summarized (Cochran 1992). The most important mechanism by which nuclides are separated from one another to create disequilibrium is their differing solubility. For U, this solubility is in turn influenced by the redox state. The process of alpha-recoil can also play an important role in producing disequilibrium. 

Conventional Systems. In the conventional antifouling compositions, the organotin compound (TBTO, TBTF, TBTC1, TBTOAc) is mechanically mixed into the paint vehicle. When the TBT species is completely soluble in the polymer matrix, factors (a) and (b) become unimportant in most cases. The mobile species is already present its diffusion in the matrix, phase transfer and migration across the boundary layer into the ocean environment may be represented by Figure 2a. When the organotin compound forms a dispersed second phase, rate of its dissolution in the polymer matrix becomes another factor to consider. 

P. D. Thacker, Global Warming s Other Effects on the Oceans, Environ. Sci. Technol. 2005,39, 10A. 

Resistant to environmental conditions. After deployment, sensors must be resistant to mechanical shocks from waves and be insensitive to, or compensate for, changes in temperature, pressure, salinity, and. biofouling that they will invariably encounter in the ocean environment. Biofouling and corrosion are major problems for instruments that are deployed for long periods of time. Appropriate sensor and instrument design, as well as selection of appropriate materials compatible with such a harsh environment, must be taken into account. 

Rarth (1952) proposed the concept of residence (passage) time of an element in the oceanic environment and formalized this concept by the equation... 

Most natural hydrates are in the ocean environment. As a state-of-the-art summary of ocean hydrates, Trehu et al. (2006) list six major lessons learned during the decade from 1996 to 2006 ... 

Remsen, C. C., Bowen, V. T., and Honjo, S. Responses by open ocean microorganisms to environmental pollution. U.S.-Japan Conf. Mar. Microbiol. Symp. Effect of the ocean environment on microbiological activities, 1-16 (1972). 

Council on The Atmospheric Chemistry Studies in the Oceanic Environment... 

Remsen, C. C., Carpenter, E. J., and Schroeder, B. W. (1972b). The role of urea in marine microbial ecology. In Effect of the Ocean Environment on Microbial Activities (ColweU, R. R., and Morita, R. Y., eds.). University Park Press, Baltimore, pp. 286—304. 

Lastly, recent studies have shown an unexpected genetic diversity among, the morphologically uniform, marine Synechococcus with at least 10 distinct clades identified (Fuller et al., 2003 Rocap et al., 2003). It needs to be established whether such Synechococcus clades represent different ecotypes adapted to different niches in the ocean environment. Moreover, little is known whether certain clades represent stable populations over seasonal cycles and/or multi-annual time periods. 

Dillon W. P. (2001) Gas hydrate in the ocean environment. In Encyclopedia of Physical Science and Technology (ed. R. Meyers). Academic Press, San Diego, vol. 6, pp. 473-486. 

Ehrlich, H.L., 1974. Response of some activities of ferromanganese nodule bacteria to hydrostatic pressure. In R.R. Colwell and R.Y. Morita (Editors), Effect of the Ocean Environment on Microbiol Activities. University Park Press, Baltimore, pp. 208—221. 

Kim, J., and C. E. Zobell (1972), Occurrence and Activities of Cell-Free Enzymes in Oceanic Environments, in R. R. Cowell and R. Y. Morita, Eds., Effect of the Ocean Environment on Microbial Activities, University Park Press, University Park, TX, pp. 368 385. 

Overall, during the past roughly four decades noble gases have significantly contributed to the field of oceanography. We anticipate that future studies will provide further extensive data sets that will form the foundation for improvement in our knowledge of a wide variety of topics. These topics reach from modem circulation of the ocean to understanding processes that shaped the oceanic environment over many millions of years. 

Because of the use of tributyl tin as a stabilizer in PVC plastic (hence an incineration source for inorganic Sn) and as an antifouling agent in marine paints, there has been some interest in the fate of anthropogenic Sn in the oceanic environment. Inorganic Sn is very low in the surface waters of the Sargasso Sea ( 3 X 10 moleskg ). Tributyl tin has been observed in enclosed harbors, but not in the open ocean. 

Martin, Lawrence. Scuba Diving Explained Questions and Answers on Physiology and Medical Aspects of Scuba Diving. Flagstaff, Ariz. Best Publishing Co., 1997. An in-depth description of the physics of decompression sickness is given in Section G of this comprehensive book on human physiology in the ocean environment. 

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