Seawater, mass

The overall effect of the terrestrial weathering reactions has been the addition of the major ions, DSi, and alkalinity to river water and the removal of O2, and CO2 from the atmosphere. Because the major ions are present in high concentrations in crustal rocks and are relatively soluble, they have become the most abimdant solutes in seawater. Mass-wise, the annual flux of solids from river runoff (1.55 x 10 g/y) in the pre-Anthropocene was about three times greater than that of the solutes (0.42 x 10 g/y). The aeolian dust flux (0.045 X 10 g/y) to the ocean is about 30 times less than the river solids input. Although most of the riverine solids are deposited on the continental margin, their input has a significant impact on seawater chemistry because most of these particles are clay minerals that have cations adsorbed to their surfaces. Some of these cations are desorbed... 

Figure 32.5 Plutonium-239+240 in environmental samples at Thule, Greenland, between 1970 and 1984, after a military accident in 1968. (Modified from Aarkrog, A. 1990. Environmental radiation and radiation releases. Inter. Jour. Radiation Biol. 57 619-631.) Within the contaminated area of 3.2 x 10 m , the fresh weight biomass of shrimps was 0.11 x 10 kg of brittle star echinoderms 0.06 x 10 kg and of clam (Macoma balthica) soft parts 0.32 x 10 kg. The seawater mass was 3 x 10 kg, and the dry weight of the upper 15-cm sediment layer was 3 x 10" kg. 

Table 70 Composition of zinc anodes for use in seawater (mass%) [208]...

The chlorinity. Cl (%e), is determined by the titration of seawater with AgNO. It was defined as the chlorine equivalent of the total hahde concentration ia g kg seawater it is now defined as the mass ia grams of Ag necessary to precipitate the halogens (Cl and Br ) ia 328.5233 g of seawater. It has been adequately demonstrated that the relative composition of the major (greater than 1 m kg seawater) components of seawater is nearly constant. By measuriag one constituent of seawater, the composition of other components can be characterized. The constituent normally selected is the chlorinity. Cl... 

Residence times were computed hy r = M/Q where M for a particular constituent is equal to its concentration in seawater times the mass of the oceans, and is equal to the concentration of the constituent in average river water times the annual flux of river water to the ocean. 

Supersulfiated cement (82) has a very low heat of hydration and low drying shrinkage. It has been used in Europe for mass concrete constmction and especially for stmctures exposed to sulfate and seawaters. 

The properties of platinum as an inert electrode in a variety of electrolytic processes are well known, and in cathodic protection it is utilised as a thin coating on a suitable substrate. In this way a small mass of Pt can provide a very large surface area and thus anodes of this type can be operated at high current densities in certain electrolyte solutions, such as seawater, and can be economical to use. 

The density of seawater is controlled by its salt content or salinity and its temperature. Salinity is historically defined as the total salt content of seawater and the units were given as grams of salt per kilogram of seawater or parts per thousand (%o). Salinity was expressed on a mass of seawater basis because mass, rather than volume, is conserved as temperature and... 

Because seawater signatures of temperature and salinity are acquired by processes occurring at the air-sea interface we can also state that the density characteristics of a parcel of seawater are determined when it is at the sea surface. This density signature is locked into the water when it sinks. The density will be modified by mixing with other parcels of water but if the density signatures of all the end member water masses are known, this mixing can be unraveled and the proportions of the different source waters to a given parcel can be determined. 

MacKenzie and Carrels (1966) approached this problem by constructing a model based on a river balance. They first calculated the mass of ions added to the ocean by rivers over 10 years. This time period was chosen because geologic evidence suggests that the chemical composition of seawater has remained constant over that period. They assumed that the river input is balanced only by sediment removal. The results of this balance are shown in Table 10-13. 

The failure to identify the necessary authigenic silicate phases in sufficient quantities in marine sediments has led oceanographers to consider different approaches. The current models for seawater composition emphasize the dominant role played by the balance between the various inputs and outputs from the ocean. Mass balance calculations have become more important than solubility relationships in explaining oceanic chemistry. The difference between the equilibrium and mass balance points of view is not just a matter of mathematical and chemical formalism. In the equilibrium case, one would expect a very constant composition of the ocean and its sediments over geological time. In the other case, historical variations in the rates of input and removal should be reflected by changes in ocean composition and may be preserved in the sedimentary record. Models that emphasize the role of kinetic and material balance considerations are called kinetic models of seawater. This reasoning was pulled together by Broecker (1971) in a paper called "A kinetic model for the chemical composition of sea water."... 

ElementAbundance in Crust(% by Mass)Abundance in Seawater(mol/L)Abundance in Plasma(mol/L)... 

C12-0107. The table lists the parts per million by mass of the principal ions in seawater ... 

At the stage of Kuroko mineralization, evolved reacted seawater enriched in Eu, Ca, and Sr formed at low seawater/rock ratio (ca. 1 by mass) and at relatively reduced condition (Eu +/Eu + greater than 1). Selective leaching of Eu, Ca and Sr occurred from the dacitic rocks underlying the Kuroko ores. The hydrothermal solution enriched... 

Wolery (1978) and Reed (1982, 1983) have indicated based on a computer calculation of the change in chemistry of aqueous solution and mineralogy during seawater-rock interactions that epidote is formed under the low water/rock ratio less than ca. 50 by mass. Humphris and Thompson (1978), Stakes and O Nell (1982) and Mottl (1983) have also suggested on the basis of their chemical and oxygen isotopic data of the altered ridge basalts that epidote is formed by seawater-basalt interaction at elevated temperatures (ca. 200-350°C) under the rock-dominated conditions. If epidote can be formed preferentially under such low water/rock ratio, the composition of epidote should be influenced by compositions of the original fresh rocks. 

Fig. 2.47. Model predicting mineral assemblages and proportions produced when basalt reacts with seawater in different water/rock mass ratios. The model is based on experimental data but is close to actual observed assemblages in recovered greenschist facies metabasalts (Mottl, 1983).

Choi MS, Francois R, Sims K, Bacon MP, Brown-Leger S, Fleer AP, Ball L, Schneider D, Pichat S (2001) Rapid determination of °Th and Pa in seawater by desolved micro-nebulization Inductively Coupled Plasma magnetic sector mass spectrometiy. Mar Chem 76 99-112... 

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