Water-ammonia ocean

Methane, ammonia and water are found in increasing concentrations in the deeper atmosphere (Fig. 3.18). There is a mantle (see Fig. 3.17) which is liquid and with temperatures up to 2500 K consisting of a mixture of ammonia, water and methane. This zone therefore is a water-ammonia ocean and at a depth of 7000 km... 

Atreya, Baines, and Egeler, 2006 [12] investigated the existence and observational hints for an ocean of water-ammonia on Neptune and Uranus. Observational hints are from their tropospheric cloud structure and from the existence of a magnetic field of these planets that must be maintained by a dynamo action that could take place in such a water-ammonia ionic ocean. 

Atreya, S.K., Baines, K.H., Egeler, P.A. An ocean of water-ammonia on Neptune and Uranus clues from tropospheric cloud structure. In Bulletin of the American Astronomical Society, vol. 38, p. 489 (2006)... 

One form of solar heat does offer interesting possibilities and is refeiTcd to as OTEC (Ocean-Thermal Energy Conversion). The OTEC power plant principle uses the solar heat of ocean surface water to vaporize ammonia as a working fluid in a Rankine cycle. After the fluid is expanded in the turbine, it is condensed by the 22°C colder... 

Mertens etal. [11] and Stevens [12] designed semiautomated versions of the micro Kjeldahl which avoided the distillation step altogether. In their versions, after the digestion step the digestion solution was diluted and the ammonia determined with an ammonia probe. The limitation on the sensitivity, then, is the sensitivity of the ammonia probe. This limits the method to the more productive oceanic waters. 

Incident solar energy is absorbed by the surface water of the oceans. Ocean surface temperatures in excess of 26°C occur near the equator. Pure water has a maximum density at a temperature of 4°C. The chilled water tends to settle to the depths of the ocean. The combination of the warmed ocean surface water and cold deep ocean water provides the thermodynamic condition needed to operate a heat engine called ocean thermal energy conversion (OTEC). A typical closed-cycle OTEC Rankine cycle using a working fluid such as ammonia or a freon is suggested. 

There are two principal approaches to build OTEC power plants. The first approach called the open OTEC cycle involves a flash boiler to obtain steam directly from the warm surface ocean water. The open OTEC cycle requires a very large turbine. The second approach is called the closed OTEC cycle, which involves heat exchangers and a secondary thermodynamic working fluid such as ammonia or freon to reduce the size of the plant. 

OCEAN THERMAL ENERGY CONVERSION (OTEC). Utilization of ocean temperature differentials between solar-heated surface water and cold deep water as a source of electric power. In tropical areas such differences amount to 35-40°F. A pilot installation now operating near Hawaii utilizes a closed ammonia cycle as a working fluid, highly efficient titanium heat exchangers, and a polyethylene pipe 2000 feet long and 22 inches inside diameter to handle the huge volume of cold water required. Alternate uses for such a system, such as electrolysis of water,... 

In the anoxic zone of the Sea ammonia increases in a similar way as hydrogen sulfide (Fig. 4) and reaches maximum concentrations of about 90-100 pM in the bottom mixed layer. The losses of combined nitrogen due denitrification and the absence of nitrification in deep waters has transformed the Black Sea into an ammonium basin, where about 98% of total inorganic nitrogen stock is composed of NH4, while in the ocean 98-99% of it belongs to NO3 [23]. 

Because NH4+ contains N at the oxidation level of proteins, it is readily assimilated by both phytoplankton and bacteria, and is a preferred N source. Ammonia oxidizers may be in competition for NH4+ with other planktonic organisms. The different physiological requirements of phytoplankton and nitrifiers probably play a role in determining exacdy where in the water column NH4+ assimilation and NH4+ oxidation occur. As explained below, most nitrification occurs within or near the base of the euphotic zone in the upper 100 or so meters of the ocean. However, there is usually very little N03 in the surface ocean, due to utilization by phytoplankton, except in high nutrient low chlorophyll regions and when supplied by episodic events such as regional upweUing. The N03 in the deep water of the oceans has accumulated from nitrification because phytoplankton assimilation is essentially zero below the euphotic zone. It is because of nitrifiers... 

Francis, C. A., Roberts, K. J., Bemen, J. M., Santoro, A. E., and Oakley, B. B. (2005). Ubiquity and diversity of ammonia-oxidizing archaea in water columns and sediments of the ocean. Proceedings of the National Academy of Sciences 102, 14683—14688. 

---