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Chapter 5: pp. 133-155

Main points of today's lecture:

• Chemical and physical properties of sea water

• Atoms, molecules, pH and density in sea water

• Dissolved substances entering the ocean by rivers

• Nutrients and dissolved gas

Insights:

• On earth, water occurs in three states which depend on temperature and pressure. Solid water or ice consists of ordered molecules tightly bonded to one another. Liquid water consists of molecules that move relative to one another. Gaseous water or vapor is made up of independently moving molecules.

• Despite its simple chemical composition H₂O, water is a complex substance capable of coexisting naturally as a gas, a solid and a liquid on earth's surface. It has an unusually high heat capacity and tremendous solvent power, which are understood in terms of the "polar" structure of water molecules.

• Seawater consists of a small quantity of salt dissolved in water. Salt occurs as charged particles, cations & anions, dispersed among water molecules. Also contained in minor amounts are a wide variety of dissolved metals, nutrients, gases and organic compounds.

• Major constituents in seawater include chloride (Cl^-) and sodium (Na⁺) which together comprise more than 85.65% of the total dissolved substances. Other major constituents include sulfate (SO₄^2- ), magnesium (Mg²⁺), calcium (Ca²⁺), and potassium (K⁺). All six make up over 99% of all of seawater's solutes.

• Salinity can be defined formally as the total mass expressed in grams of all the substances dissolved in 1 kg of seawater, when all the carbonate has been converted to oxide, all the bromine and iodine have been replaced by chlorine, and all organic compounds have been oxidized at a temperature of 480 °C, or simply as the total weight in grams of dissolved salts in 1 kg of seawater expressed as parts per thousand (^o/_oo).

• Conservative substances do not change in abundance over long periods of time.

• The major, conservative substances are present in constant proportions; that is, their relative abundances don't change from place to place in the oceans.

• Residence time for a given substance equals the total amount of it in the ocean dividied by the rate it is added (or removed) to/from the ocean.

• Density is mass/volume and varies throughout the ocean as a function of temperature and salinity.

http://dusk.geo.orst.edu/oceans/lec11.html