Chloride concentration ocean

Chlorine. Nearly all chlorine compounds are readily soluble in water. As a result, the major reservoir for this element in Figure 1 is the ocean (5). Chloride, as noted earHer, is naturally present at low levels in rain and snow, especially over and near the oceans. Widespread increases in chloride concentration in mnoff in much of the United States can be attributed to the extensive use of sodium chloride and calcium chloride for deicing of streets and highways. Ref. 19 points out the importance of the increased use of deicing salt as a cause of increased chloride concentrations in streams of the northeastern United States and the role of this factor in the chloride trends in Lake Ontario. Increases in chloride concentration also can occur as a result of disposal of sewage, oil field brines, and various kinds of industrial waste. Thus, chloride concentration trends also can be considered as an index of the alternation of streamwater chemistry by human development in the industrialized sections of the world. Although chlorine is an essential element for animal nutrition, it is of less importance for other life forms. 

Both solubilities are low, as we would expect for a salt with a small value of. S sp. Notice that PbCl2 is about 350 times less soluble in the NaCl solution. This makes sense in terms of the common-ion effect. The excess chloride ion suppresses the solubility of Pb by Le Chatelier s principle. The actual concentration of lead in seawater is much less than 4.0 X 10 M. This is because other lead salts are much less soluble than lead(II) chloride. The ocean contains carbonate, for example, and. STsp for lead(II) carbonate is quite small, 7.4 X lO ". ... 

Vacher, H.L. and Ayers, J.F. (1980) Hydrology of small oceanic islands — utility of an estimate of recharge inferred from the chloride concentration of the freshwater lenses. Jour. Hydrol. 45, 21-37. 

Sea-salt inputs are common in coastal regions. These salts have been introduced into the marine atmosphere from bubble bursting and breaking waves and are deposited on land with rain and dust fall. Small amounts of sea-salts are, however, also present in rainwater of central continental areas, thousands of miles from the sea. Sea-salt inputs have broadly similar, predominantly sodium chloride (NaCl), chemistry to the seawater from which they were derived. Thus, sodium or chloride ions can be used as a measure of sea-salt inputs to rainwater. Chloride concentrations in rain falling on oceanic islands are around 200pmolh, rain within 100 km of coastal continental areas contains around 10-100 pmolT1, while further inland chloride concentrations fall below 10 nmol I, but not to zero. 

The dissociation of gas hydrate leaves another indirect marker of its former existence, because when gas hydrate forms it extracts pure water to form the clathrate structure, excluding all salts as brine. Therefore, when hydrate dissociates in a core, the interstitial water becomes much fresher, and the amount of gas hydrate present before dissociation can be calculated. An example is shown in Fig. 4 from Ocean Drilling Program hole 997 off the South Carolina coast. Measured chloride content is shown in the left panel. The values near zero depth (depth at the seafloor) represent seawater chloride concentration (chlorinity). It is assumed that a smooth curve of chlorinity vs depth, following the main trend of data points (solid curve), rep-... 

Chlorine is the twentieth most abundant element in crustal rocks where it occurs to the extent of 126 ppm (cf. nineteenth V, 136 ppm, and twenty-first Cr, 122 ppm). The vast evaporite deposits of NaCl and other chloride minerals have already been described (pp. 69, 73). Dwarfing these, however, are the inconceivably vast reserves in ocean waters (p. 69) where more than half the total average salinity of 3.4 wt% is due to chloride ions (1.9 wt%). Smaller quantities, though at higher concentrations, occur in certain inland seas and in subterranean brine wells, e.g. the Great Salt Lake, Utah (23% NaCl) and the Dead Sea, Israel (8.0% NaCl, 13.0% MgCU, 3.5% CaCU). 

Ocean sea water is roughly equivalent in strength to a 3 j % w/v solution of sodium chloride, but it has a much more complex composition, embodying a number of major constituents, and traces at least of almost all naturally occurring elements. For convenience, however, the concentration of salts in any sample of sea water is expressed in terms of the chloride content, either as chlorinity or as salinity. Both these units are again subject to arbitrary definition and do not conform simply to the chemical composition. 

In all the experiments, the main decomposition products were phosphonates, which are also stable in concentrated solutions of Mg and Ca chlorides. In some experiments, pyrophosphate, and in smaller amounts triphosphate, could also be detected. The authors thus assume that the primeval ocean contained phosphonates as a source of phosphorus for reactions leading to biochemically relevant molecules. Iron meteorites could have delivered sufficient reduced phosphorus (Fe3P) to the primeval Earth, so the question of prebiotic phosphorus chemistry should be looked at in more detail in the future (Pasek and Lauretta, 2005). 

Lovelock and co-workers [228,229] determined methyl fluoride, methyl chloride, methyl bromide, methyl iodide, and carbon tetrachloride in the Atlantic Ocean. This shows a global distribution of these compounds. Murray and Riley [230,231] confirmed the presence of carbon tetrachloride, and also found low concentrations of chloroform and tri- and tetrachloroethylene in Atlantic surface waters. 

Similar elements also occur in the same natural environment. For instance, the halogens are markedly concentrated in seawater. (The major salt in ocean brines is sodium chloride.) The other halogens are extracted from seawater that has been further concentrated—bromine from salt beds formed by evaporation and iodine from kelp, which grows in oceans. 

Sodium chloride is widely distributed in nature. Oceans are the vast source of sodium chloride. It occurs in seawater at an average concentration of 2.68 wt%. It also occurs in many inland saline waters and in salt deposits in sedimentary rocks, as the mineral hahte. 

Thousands of tonnes of methyl chloride are produced naturally every day, primarily in the oceans. Other significant natural sources include forest and brush fires and volcanoes. Although the atmospheric budget of methyl chloride can be accounted for by volatilization from the oceanic reservoir, its production and use in the manufacture of silicones and other chemicals and as a solvent and propellant can make a significant impact on the local atmospheric concentration of methyl chloride. It has been detected at low levels in drinking-water, groundwater, surface water, seawater, effluents, sediments, in the atmosphere, in fish samples and in human milk samples (Holbrook, 1993 United States National Library of Medicine, 1998). Tobacco smoke contains methyl chloride (lARC, 1986). 

Seawater is unfit for drinking or agriculture because each kilogram contains about 35 g of dissolved salts. The most abundant salt in seawater is sodium chloride, but more than 60 different elements are present in small amounts. Table 14.3 lists the ions that account for more than 99% of the mass of the dissolved salts. Although the oceans represent an almost unlimited source of chemicals, ion concentrations are so low that recovery costs are high. Only three substances are obtained from seawater commercially sodium chloride, magnesium, and bromine. 

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