Sea water, average

The sea water in this area is enriched in some metals compared with the world average sea water. Especially, iron and man nese are present in higher quantities, the iron quantity is several times larger than the quantity of manganese. The patchy distribution of this enrichment seems to be caused by the colloidal stage of iron and manganese hydroxides ... 

In average sea water the " Ra content is about 0.2 dpm/1 and (or is about 2 dpm/1. The uranium usually presents no problem, but a good separation of the final from Ra and its daughters is important, especially for deep ocean water. During the separation steps, this procedure effectively removes all radionuclides that are chemically similar to yttrium or rare earths from the Sr fraction and, after the establishment of Sr/ Y radioactive equilibrium, the final purification steps further remove any interfering radionuclides in the ingrowth Y fraction before measurement by beta counting. 

Table 1 The major constituents of average sea water with a salinity of 35...

Element (M) Average crustal Average sea water Sea water (M/A/)sw (M/AI) ... 

The pressure to be used for reverse osmosis depends on the salinity of the feedwater, the type of membrane, and the desired product purity. It ranges from about 1.5 MPa for low feed concentrations or high flux membranes, through 2.5—4 MPa for brackish waters, and to 6—8.4 MPa for seawater desalination. In desalination of brackish or sea water, typical product water fluxes through spiral-wound membranes are about 600—800 kg/m /d at a recovery ratio RR of 15% and an average salt rejection of 99.5%, where... 

Variations of salinity In the major oceans the salinity of sea water does not vary widely, lying in general between 33 and 37 parts per thousand, a figure of 35 parts per thousand, equivalent to 19-4 parts per thousand chlorinity is commonly taken as the average for open-sea water. 

In extended exposure periods of up to 16 years in tropical sea water, Southwell and Alexander obtained an average corrosion rate for steel of 0-18 mm/y in the first year, falling off to a constant rate after 4 years at 0-025 mm/y. They also quote pitting rates as 1 mm/y in the first year falling... 

A comprehensive table of corrosion rates in sea water has been compiled by LaQue . This appears to show no obvious dependence of corrosion rates on the geographical location of the testing site, and few of the rates depart widely from an average of 0-11 mm/y. It is suggested that a figure of 0-13 mm/y may be taken as a reasonable estimate of the expected rate of corrosion of steel or iron continuously immersed in sea water under natural conditions, in any part of the world. 

This is presumably an estimated average curve, as no numerical data are quoted, and it may be assumed to refer to bare steel. This conclusion is not supported by the results of Volkening, whose main interest was in the effect of chlorination and who shows that although corrosion increased with velocity of chlorinated sea water, when plain sea water was used velocity had little effect. There can be no doubt that painting will very much reduce the effect of water speed, as also will marine fouling or slime. 

The average rates of corrosion of Fe-36Ni alloy exposed to alternate immersion in sea-water are appreciably greater than those that occur when the alloy is exposed to marine atmospheres. Although the rates of corrosion are significantly below those observed for mild steel (Table 3.32) the superiority over mild steel in not so great with respect to pitting attack. 

Nickel-iron alloys fully immersed in sea-water may suffer localised corrosion which can be severe under conditions where oxygen is constantly renewed at the surface and the formation of protective corrosion products is hindered, e.g. in fully-aerated flowing sea-water. In quieter, less oxygenated conditions, average corrosion rates of Fe-36Ni are low and well below those for mild steel, as exemplified in the data given in Table 3.33 . However the resistance to localised attack is not improved to the same extent. 

The rate of corrosion of unpainted mild steel immersed in sea-water was found by Hudson and Banfield to be 0 089mm/y. Hudson obtained a similar average value for steel exposed in the open air under industrial conditions (0 051 mm/y at Motherwell and 0- 109mm/y at Sheffield). This rate of corrosion corresponds to the destruction of 0-07 g/cm per year of iron. Assuming that the corrosion product was FcjOj.HjO, this rate of... 

Approximately 70 elements can be found in sea water, however, only in minuscule amounts. Among these elements is gold. Unfortunately, the average gold content is around 0.01 mg/m3. 

Leoni [366] observed that in the extraction preconcentration of organochlo-rine insecticides and PCB s from surface and coastal waters in the presence of other pollutants such as oil, surface active substances, etc., the results obtained with an absorption column of Tenax-Celite are equivalent to those obtained with the continuous liquid-liquid extraction technique. For non-saline waters that contain solids in suspension that absorb pesticides, it may be necessary to filter the water before extraction with Tenax and then to extract the suspended solids separately. Analyses of river and estuarine sea waters, filtered before extraction, showed the effectiveness of Tenax, and the extracts obtained for pesticide analysis prove to be much less contaminated by interfering substances than corresponding extracts obtained by the liquid-liquid technique. Leoni et al. [365] showed that for the extraction of organic micro pollutants such as pesticides and aromatic polycyclic hydrocarbons from waters, the recoveries of these substances from unpolluted waters (mineral and potable waters) when added at the level of 1 xg/l averaged 90%. 

The global average production rate of any nuclide, Q(t), at any time, t, will be primarily dependent on the cosmic ray intensity, I(t). If the intensity varies sinusoidally with a period T(u) = 2n/T), Q(t) will also vary sinusoidally. The standing crop of a nuclide in the sea water column for a production function, Q(t) = Q (1 + a cos tot), a being the amplitude, can be deduced to be 0... 

The flotation feed at the Valkoomesky plant contains tourmaline (18%), biotite (13%), muscovite (17%), limonite (2%) and sulphides (5%). Tin assays in the flotation feed averaged about 0.5% Sn, of which the bulk was contained in the -48 to +12 pm fractions. Flotation of tin was carried out with sea water using oxidized petroleum solution in kerosene (1 2 ratio). 

Arias, 1999 Haslbeck and Holm, 2005). Both methods are based on a painted polycarbonate rotating cylinder immersed into a holding tank in which artificial sea water of known composition is kept at relatively constant conditions (see Table 1). At specific time intervals, the cylinder is immersed into a 1.5 litre tank where they are rotated for typically 1 hour, after which the total copper released is determined. In this way, copper release rate vs. time curves are obtained. Typically, the average release rate value between day 21 and 42/45 and the accumulated release rate during the first 14 days of exposure are used to compare the different paint systems. 

GaUium is widely distributed in nature, mostly found in trace amounts in many minerals including sphalerite, diaspore, bauxite, and germanite. It is found in aU aluminum ores. Gallium sulfide occurs in several zinc and germanium ores in trace amounts. It also is often found in flue dusts from burning coal. Abundance of this element in the earth s crust is about 19 mg/kg. Its average concentration in sea water is 30 ng/L. 

Hafnium was discovered in 1922 by Coster and deHevesy. They named it for Hafnia, the Latin word for Copenhagen. It is found in aU zirconium ores, such as zircon, (ZrSi04) and baddeleyite (Zr02). It occurs in the earth s crust at about 3 mg/kg. Its average concentration in sea water is 7 ng/L. 

The element does not occur in nature in native form. Its principal mineral is cinnabar, the red mercuric sulfide, HgS. Black mercuric sulfide, metacinnabar, also is found in nature. Other ores are hvingstonite, HgSh4S coloradite, HgTe tiemannite, HgSe and calomel, HgCl. Its concentration in the earth s crust is estimated to be 0.08 mg/kg. The average concentration in sea water is about 0.03 ag/L. 

The abundance of niobium in the earth s crust is estimated to be in the range 20 mg/kg and its average concentration in sea water is 0.01 mg/L. The metal also is found in the solar system including the lunar surface. Radionucleides niobium-94 and -95 occur in the fission products of uranium-235. 

Several ores containing potassium chloride are found commonly in nature. The principle ores are sylvite, KCl carnalhte, KCl MgCl2 6H20 kainite, KCl MgS04"3H20 and sylvinite, a naturally occuring mixture of sylvite and halite (common salt). Potassium chloride also is found in sea water at an average concentration of 0.076% (w/v). 

Strontium is found in small quantities in many rocks and soils, mostly associated with calcium and barium. Its abundance in the earth s crust is about 370 mg/kg, about the same as barium. The average concentration of this metal in sea water is about 7.9 mg/L. 

Zinc occurs in nature, widely distributed. The principal ores are sphalerite (and wurtzite) known as zinc blende, ZnS gahnite, ZnAl204 calamine smith-sonite, ZnCOs franklinite, ZnFe204 and zincite, ZnO. Abundance in earth s crust is about 70 mg/kg and average concentration in sea water is about 10 pg/L. 

Sea level rise. With increasing surface temperatures the average sea level will rise because of three factors melting of polar ice caps, receding of glaciers, and thermal expansion of the ocean surface waters. Combining all three factors,... 

Sverdrup et al. (1942) estimated that the oxygen content of deep sea water averages about 2.5 cubic centimeters at standard temperature and pressure pa liter (0.1 mole per cubic meter). Thus, there are about 250... 

The mica phase contains mainly K and Mg and little Ca or Na. The field IL contains both the average composition of illites (14) given by Brown (4), the analysis of illite, treated with sea water (23), and that of the illitic fraction prepared from montmorillonite according to White-... 

Table I. Average Composition Data for Major Constituents of Sea Water (36)...

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