The purpose of this report is to provide a basis for predicting the composition of elements at any depth or location in the world oceans. Our aim is not to assess the importance of variations in elemental concentrations but only to provide a method of estimating them. The method, however, provides no entry into the problem of estimating the effects of local releases from sediments or of human activity.
The salinity of the open ocean ranges between 33‰ and 38‰ Dittmar  showed that despite this variation in total salt concentration the proportions of the different ions making up most of the salt content were remarkably constant. In that sense these ions are identified as being ‘conservative’; that is, their variation is ascribed exclusively to the addition or subtraction of pure water to a saline solution of fixed elemental proportions. The concentrations of certain trace elements also have been shown to correlate with chlorinity within analytical errors and these too can be classified as behaving conservatively.