Hydrosphere, mass

The hydrosphere (the Greek prefix hydro means water) is the great mass of water that surrounds the crust of the earth. Water is one of a few substances that, at the temperatures normal on the surface of the earth (which range between about -50 and 50°C), exists in three different states liquid, gas, and solid. Liquid water makes up the oceans, seas, and lakes, flows in rivers, and underground streams. Solid water (ice) occurs in the polar masses, in glaciers, and at high altitudes, and gaseous water (moisture) is part of the atmosphere (O Toole 1995). Liquid and solid water cover over 70% of the surface of the earth. 

As geochemists, we frequently need to describe the chemical states of natural waters, including how dissolved mass is distributed among aqueous species, and to understand how such waters will react with minerals, gases, and fluids of the Earth s crust and hydrosphere. We can readily undertake such tasks when they involve simple chemical systems, in which the relatively few reactions likely to occur can be anticipated through experience and evaluated by hand calculation. As we encounter more complex problems, we must rely increasingly on quantitative models of solution chemistry and irreversible reaction to find solutions. 

The elements whose isotopes are routinely measured with gas inlet mass spectrometers are carbon (12C and 13C, but not 14C), oxygen (160, 170, l80), hydrogen ( H, 2H, but not 3H), nitrogen (14N and 1SN) and sulphur (32S, 33S, 34). Stable isotopes of H, C, N, O, and S occur naturally throughout atmosphere, hydrosphere, lithosphere, and biosphere. They are atoms of the same elements with a different mass. Each element has a dominant light isotope with the nominal atomic weight (I2C, 160,14N, 32S, and H) and one or two heavy isotopes (l3C, nO, 180, 15N, 33S, 34S, and, 2H) with a natural abundance of a few percent or less Table 1). 

The 8180 value of modern seawater (sw) is 0% while the average 5180 value of polar ice caps is —45%. Calculate the 8lsO value of the ice-free ocean obtained upon melting the polar ice caps, i.e., the bulk value of the hydrosphere. Assume that ice caps hold a fraction fct = 2 percent in mass of the terrestrial waters and that other water reservoirs (e.g., ground water) can be neglected. 

Table 8.1 shows the general distribution of water masses in the hydrosphere. Although H2O occurs mainly in oceans, 19% of the earth s H2O mass is still trapped in lithospheric rocks. A nonnegligible H2O mass (about 1%) is also fixed in crystalline form as ice. 

Water is among the most important compounds on earth. It is the main constituent of the hydrosphere, which along with the mantle, crust, and the atmosphere are the four components of our planet. It is present everywhere on earth and is essential for sustenance of life. Water also determines climate, weather pattern, and energy balance on earth. It also is one of the most abundant compounds. The mass of all water on earth is l.dxlO i kg and the total volume is about l.dxlO km, which includes 97.20% of salt water of oceans, 2.15% of fresh water in polar ice caps and glaciers, 0.009% in freshwater lakes, 0.008% in saline lakes, 0.62% as ground waters, 0.005% in soil moisture 0.0001% in stream channels and 0.001% as vapors and moisture in the atmosphere. 

Natural Pollution of the Oceans, Frequently overlooked is what may be termed natural 1 pollution, which, when coupled with artificial (anthropogenic) pollution, contributes to the sum total of all pollutants found in fresh and ocean waters worldwide. Deep fissures in the ocean floor, fumaroles, and seamounts (underwater volcanoes) release megatons of sulfur-laden and other noxious gases into ocean water other discontinuities in the ocean basins release vast quantities of crude oil and other hydrocarbons. Surface volcanoes are major contributors to atmospheric pollution, much of which ultimately affects Earth s hydrosphere. The present dissolved solids content of the oceans represents natural water pollution that has taken place ever since the land masses rose above sea level—through a constant erosion of soil. 

On a mass basis, oxygen constitutes 23% of the atmosphere (21% by volume), 46% of the lithosphere (the earth s crust), and more than 85% of the hydrosphere. In the atmosphere, oxygen is found primarily as 02, sometimes called dioxygen. The oxygen in the hydrosphere is in the form of H20, but enough dissolved 02 is present to maintain aquatic life. In the lithosphere, oxygen is combined with other... 

Li Y-H. (1972) Geochemical mass balance among lithosphere, hydrosphere and atmosphere. Amer. J. Sci. 272, 119-137. 

In computing the average of the whole crust the relative proportions estimated by one of us2 some years ago were adopted. The latest estimates of the masses and compositions of the hydrosphere and atmosphere have been used. These relative masses are as follows Lithosphere 93% hydrosphere 7% atmosphere 0.03%. 

Despite the popular expression, you can t carry the world on your shoulders Scientists estimate that the lithosphere, or solid Earth, has a mass of 6.0 x 1024 kg. The hydrosphere, or the portion of Earth covered by water, has an estimated mass of 1.4 x 1021 kg. 

Environmental monitoring of nuclear contamination, including the determination of the concentration and isotope ratios of long-lived radionuchdes, such as uranium, plutonium isotopes, thorium, Np, Se, Sr, I and others, at trace and ultratrace levels, is a fast growing and fascinating application field for inorganic mass spectrometry." " Among the environmentally important radionuclides, I, Sr, uranium and transuranium elements are of special importance. For example, the natural I inventory in the atmosphere, hydrosphere and biosphere has been estimated to be about 263 kg. ... 

Horizontal and vertical mass transfer in the atmosphere, hydrosphere, and lithosphere, follow-... 

As introduced above, the interaction between the hydrosphere and the lithosphere frequently results in mass exchange. In this way rocks get dissolved, sediments build-up, stalactites and stalagmites form, materials get transported, and so on. The pH of water and of sediments determines the mobility and solubility of different elements, which may in turn modify the redox potential of the aqueous medium. For example, aluminum, calcium, magnesium, iron, manganese, and other metals become more soluble at low pH if pH increases, their solubility decreases and precipitation occurs. 

Of particular importance is the contamination of soil, because it receives pollutants from the atmosphere (e.g., sulfates and nitrates resulting from oxidation of nitrogen and sulfur oxides, and metals from smelters) and from the hydrosphere (e.g., sediments that concentrate heavy metals from aqueous bodies and mining operations). In multimedia mass-balance models, soil is an important sink as well as a conduit for mass transfer to vegetation and shallow groundwater. 

If the scheme of a steady-state ocean is adopted, in which volatile components (mainly HCl and CO2) occurred from the beginning in the same proportions in which they are now found in the lithosphere and hydrosphere, then the original solution would have been hydrochloric acid saturated with CO2 at high pressure. On the basis of calculations of mass made by Garrels... 

Only if it is presumed that the mass of the hydrosphere remained more or less constant in geologic history, and CO2 and HCl continually arrived from the mantle and gradually accumulated in the hydrosphere and atmosphere, will the characteristics of the primordial ocean be different. Taking the initial masses of CO2 and HCl to have been ten times less than at present (mco 250-10 ° g and Pco 5 bar mjjc, = 50-10 ° g and P q = 1 bar)... 

Table IV gives the composition of the Precambrian ocean after neutralization of HCl, calculated under these assumptions. The pH values correspond to the end of congruent solution of the original rocks of the Earth s crust and beginning of deposition of the carbonate and silicate facies of the BIF (amorphous sediments). The values of correspond to the beginning of deposition of FeCOj (first value) and the beginning of deposition of Fe3Si205(OH)4 (second value). The values of the sum of carbonate ions in solution (2C02. ) are consistent with the values of co, in the atmosphere. Questions of the proportion of the masses of CO2 m the atmosphere, hydrosphere, and carbonate sediments will be considered in more detail later.

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