ABSTRACT
Introduction When the first systematic measurements of the chemical composition of sea water were made as part of the work of the Challenger Expedition of 1872-1876, the constituents which could be analysed with any accuracy were very limited in number. They comprised some of the more abundant dissolved salt components (Figure 11.1) and certain dissolved gases. Subsequent advances in analytical chemical techniques, allied with improved methods of sampling, gradually enabled a fuller knowledge of the concentrations of a wider range of constituents to be acquired. These advances accelerated remarkably from about the mid 1970s, so that there is now information not only on the concentrations, but also on the patterns of oceanic distribution for the majority of the elements. Information on the concentrations of some important dissolved elements in sea water is given in Table 11.1.
