Encyclopedia of Environmental Science and Engineering, Volume I and II

1300 WATER: PROPERTIES, STRUCTURE, AND OCCURRENCE IN NATURE

Because the relationship between geological environment

and water composition depends upon so many interdependent

variables, and because there is no substantial variation in each

genetic type of water, no reliable generalizations are possible

with such a small number of examples. A few qualitative char-

acteristics are apparent from Table 6. As expected, ground

waters have higher ionic strengths than surface waters. This

results from the difference in CO 3 partial pressure to which

these two types of waters are exposed. In comparing waters

Nos. 5, 6 and 7, the influence of calcium plagioclase, which is

less stable than the silicic rocks, becomes apparent. Sandstone

beds are important aquifers and as sedimentary rocks may

often contain carbonates besides grains of quartz. Thus the

pH of sandstone waters tends to be higher than that of waters

from igneous rocks. Shales are laminated sediments whose

constituent particles have sizes similar to those of clay. Most

of these fine-grained sediments were deposited in saline envi-

ronments. The relatively high HCO 3  concentrations of slate

ground waters may be due to high CO 2 concentrations result-

ing from oxidation of organic carbon. Waters from limestone

and dolomite contain substantial quantities of Ca^2 ^ , Mg^2 ^ , and

HCO 3 , the concentrations of which are usually controlled by

carbonate equilibria.

The Composition of the Ocean–Atmosphere System

Goldschmidt (1933) suggested that for each liter of presently

existing sea water, 600 grams of igneous rocks had reacted

with about 1 kilogram of volatile substances (H 2 O, HCL,

CO 2 , etc.). Concomitantly formed during this process were

about 600 grams of sediments and three liters of air.

As seen in Figure 10, the solute proportion introduced by

rivers differs from that in seawater; in other words, simple

concentration of freshwater does not produce ocean water.

An important group of constituents of the ocean-atmosphere

system (Cl^ ^ , N 2 , rare gases) is controlled largely by degassing

of the earth. The concentration of O 2 is controlled by the

biological reactions of photosynthesis and respiration.

Mineral reactions control the concentrations of major cations.

Many constituents (e.g., CO 2 , O 2 , NO 3 ,HPO 4 , and H 4 SiO 4 )

are involved in biological cycles in the sea; their distribution

and redistribution depend upon the physical circulation of the

water and the settling and mineralization of plankton.

Water as a Life Preservation System; Photosynthesis

and Respiration

Photosynthesis may be viewed conceptually as an energy

consuming process leading to products of high oxidation

intensity (organic matter). Respiration is the reverse reac-

tion, the combination of the products of photosynthesis with

the release of energy. The photosynthesisrespiration reac-

tion may be written (simplified) as

CO 22 H O CH O O.

photosynthesis

respiration^22



In the aquatic environment the reaction may be written more

precisely to include trace elements and to reflect the consti-

tution of algal protoplasm.

106CO 16NO HPO 122H O 18H

C H O N P 138O

234

2

2R

P

106 263 110 16 1 2

 



 

..

The relationship between photosynthesisrespiration and the

nutrient cycle is seen in Figure 12.

The distribution of chemical species in the waters and in the

sediments are strongly influenced by an interaction of mixing

cycles and biological cycles. Radio-isotope measurements

may often be used to establish the time scale of some of these

processes. Similarly, evaluation of the fractionation of stable

Nutrients (C

hiefly Organic)

Nutrien

ts (Chiefly inorganic)

Waste

O 2 O 2

CO 2 CO 2

Photosynthesis Respiration

P

Production of

Organic Material

R

Destruction of

Organic Material

Sunlight

for other Electron Acceptors

1

Heat

FIGURE 12 Photosynthesis and the nutrient cycle. Solar energy and inorganic

nutrients including inorganic runoff are converted by photosynthesis into chemi-

cal energy stored within the organic material of algae and plants. Heterotrophic

consumers and bacteria mobilize this energy by degrading the organic nutrients

including organic waste during respiration and other oxidative process. A steady

state of continuous circulation of biochemical materials is indicative of unpol-

luted water.

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