1.2 Physical and Chemical Properties of Sea Water
13
Usually, the oxygen concentration at the ocean surface, in the photic zone,
is very close to its saturation level, and the concentration varies from about
4.5 ml per litre in tropical latitudes to more than 8 ml per litre in polar seas
(Harvey, 1985). Oxygen concentration profiles with depth are very complex
and dependent upon the location. Typical vertical distributions of dissolved
oxygen in the oceans are given in Fig. 1.5.
Oceans provide a great reservoir for carbon dioxide. As follows from Eq. 1.6,
carbon dioxide plays the reverse role to oxygen in the photosynthesis process
and is utilized by respiration. The distribution of CO2 in the ocean is controlled
mainly by formation of carbonic acid through reaction with the water. This
acid and the carbonate ions brought into the ocean by rivers (for example,
flowing over limestone CaC03) react as follows (Harvey, 1985):
(l.7)
These reactions can produce supersaturation of the water with respect to the
carbonate ion. This results in the removal of calcium carbonate by organisms
whose remains eventually settle to the ocean floor. On the other hand, undersaturation will dissolve such sediments, reducing the calcium carbonate content
of sediment, particularly at great water depths.
1.2.6 Concentration of Suspended Particles and Yellow Substances
Large varieties of suspended solid particles are present in the oceans and seas.
This suspended matter comprises organic particles of biological origin and inorganic particles of mineralogical origin, and the concentration of suspended
mass varies with locality as shown in Table 1.3.
Organic suspended material includes bacteria, fungi, phytoplankton and zooplankton. Bacteria and colloids are the smallest suspended particles in the sea,
being less than 1 micron in size. The concentration of organic substances in
sea water ranges from 0.05 to 0.5 mg/dm 3 for water in clean open oceans to
about 5 mg/ dm 3 for waters in enclosed seas and estuarine areas.
Many organic substances are carried into the sea by rivers, both in solution
and in suspension. Heavy substances in suspension fall to the bottom close to
shore and are subjected to further possible chemical reactions. As the sea and
river waters have different ionic compositions, the substances dissolved in the
river water are flocculated to a high degree on the contact with sea water to form
colloids and fine suspensions. The coagulation process is a function of salinity
and it affects the largest flocs (Gibbs and Konwar, 1986; Wolanski and Gibbs,
1995). Observations at the Amazon River estuary indicate that the mean
diameter of suspended particles supplied by the river progressively increases
seaward until a maximum is reached at about 10 ppm salinity. This results from
the coagulation of small particles as they encounter ocean water. Seaward of 10
ppm salinity in the surface waters, the mean diameter of suspended particles
decreases due to the settling of larger flocs. The maximum floc sizes are of the
13
Usually, the oxygen concentration at the ocean surface, in the photic zone,
is very close to its saturation level, and the concentration varies from about
4.5 ml per litre in tropical latitudes to more than 8 ml per litre in polar seas
(Harvey, 1985). Oxygen concentration profiles with depth are very complex
and dependent upon the location. Typical vertical distributions of dissolved
oxygen in the oceans are given in Fig. 1.5.
Oceans provide a great reservoir for carbon dioxide. As follows from Eq. 1.6,
carbon dioxide plays the reverse role to oxygen in the photosynthesis process
and is utilized by respiration. The distribution of CO2 in the ocean is controlled
mainly by formation of carbonic acid through reaction with the water. This
acid and the carbonate ions brought into the ocean by rivers (for example,
flowing over limestone CaC03) react as follows (Harvey, 1985):
(l.7)
These reactions can produce supersaturation of the water with respect to the
carbonate ion. This results in the removal of calcium carbonate by organisms
whose remains eventually settle to the ocean floor. On the other hand, undersaturation will dissolve such sediments, reducing the calcium carbonate content
of sediment, particularly at great water depths.
1.2.6 Concentration of Suspended Particles and Yellow Substances
Large varieties of suspended solid particles are present in the oceans and seas.
This suspended matter comprises organic particles of biological origin and inorganic particles of mineralogical origin, and the concentration of suspended
mass varies with locality as shown in Table 1.3.
Organic suspended material includes bacteria, fungi, phytoplankton and zooplankton. Bacteria and colloids are the smallest suspended particles in the sea,
being less than 1 micron in size. The concentration of organic substances in
sea water ranges from 0.05 to 0.5 mg/dm 3 for water in clean open oceans to
about 5 mg/ dm 3 for waters in enclosed seas and estuarine areas.
Many organic substances are carried into the sea by rivers, both in solution
and in suspension. Heavy substances in suspension fall to the bottom close to
shore and are subjected to further possible chemical reactions. As the sea and
river waters have different ionic compositions, the substances dissolved in the
river water are flocculated to a high degree on the contact with sea water to form
colloids and fine suspensions. The coagulation process is a function of salinity
and it affects the largest flocs (Gibbs and Konwar, 1986; Wolanski and Gibbs,
1995). Observations at the Amazon River estuary indicate that the mean
diameter of suspended particles supplied by the river progressively increases
seaward until a maximum is reached at about 10 ppm salinity. This results from
the coagulation of small particles as they encounter ocean water. Seaward of 10
ppm salinity in the surface waters, the mean diameter of suspended particles
decreases due to the settling of larger flocs. The maximum floc sizes are of the