All symbols used in the present work are defined at the appropriate place in the text, which can be found by reference to the index at the end of the volume. The units defined below, and the symbols by which they are identified, are confined to a general list of those most commonly used in the present work; other units will be defined where necessary in the text itself. It must be noted that a number of traditional units have been retained as a matter of policy throughout the work because they are still widely used in the current as well as in the past literature; e.g. the litre has been used as a unit volume although IAPSO have recommended that for high-precision measurements of volume it be replaced by the cubic decimetre (dm3). For a detailed treatment of the use of SI units in oceanography see the IAPSO recommendations published by Unesco (1985). <...>

The oceans of the world represent a natural depository for the dissolved and particulate products of continental weathering. After its input, the dissolved material consolidates by means of biological and geochemical processes and is deposited on the ocean floor along with the particulate matter from weathered rock. The ocean floor deposits therefore embody the history of the continents, the oceans and their pertaining water masses.

The field of marine chemistry and geochemistry has developed dramatically since the end of World War II. Mainly this spurt of refinement was the consequence of the development of novel techniques of measurement of both radioactive and radiogenic isotopes as well as the light stable isotopes.

The fundamental question underlying marine geochemistry is, ‘How do the oceans work as a chemical system?’ At present, that question cannot be answered fully. The past four decades or so, however, have seen a number of ‘quantum leaps’ in our understanding of some aspects of marine geochemistry. Three principal factors have made these leaps possible:
1    advances in sampling and analytical techniques;
2    the development of theoretical concepts;
3    the setting up of large-scale international oceanographic programmes (e.g. DSDP, MANOP, HEBBTE, GEOSECS, TTO, VERTEX, JGOFS, SEAREX, WOCE), which have extended the marine geochemistry database to a global ocean scale. <...>