A Practical Handbook of Seawater Analysis, 2nd edition.

Abstract

The basic purpose of the book is unchanged. It is not designed as a compendium of methods of seawater analysis but consists of full working instructions of certain procedures used by the authors and their colleagues in the laboratory and at sea and found by them to be reliable and to have an adequate sensitivity and precision for most studies of marine ecology. The reason for using one approach in favour of another is not always stated, as often it was a matter of judgment and preference on the part of the authors. Some of the methods are taken directly from the literature with only the slight modifications of solution volumes and concentrations necessary for convenient shipboard use. In many instances, however, the original procedures have been greatly modified where this has been found to result in an increase of speed, precision, or operational simplicity. A number of the methods constitute a completely new application of analytical techniques to marine chemistry. Although a measurement of the photosynthetic potential of a sample of sea water or of the growth rate of suspended matter is not strictly seawater analysis, these determinations are becoming increasingly important in many marine laboratories and we have taken the opportunity to include a short section on some of the basic procedures involved. Most of the methods described in this book are for substances that affect or measure organic production in the sea and, in most cases, the methods can be mastered by relatively inexperienced workers in a ship's laboratory. In general the procedures require only simple apparatus but we have included in this new book some approaches which necessitate the use of more highly specialized equipment. This book does not, however, attempt to treat comprehensiveiy the analysis for transitional and "rare" metallic elements, which are mainly of geochemical interest, although we have retained methods for iron, manganese, and copper unchanged from earlier issues. These methods are simple and reliable but more sensitive ones can now be found in the literature. Automation in seawater analysis is at last a reality but methods and equipment are still in the exploratory stages. We have now accumulated more than 2 years of sea-going experience with automation so that a brief outline of the methodology used by us may prove to be a worthwhile introduction to the subject. Although the presence of 3.5% dissolved salts in the ocean gives rise to many analytical difficulties, the relative constancy of composition and ionic environment of sea water has the advantage that one method will generally be applicable to sa waters of all normal salinities. The methods given here are designed solely for ea water and should be used with caution if applied to the analysis of lake water, brackish waters, or water heavily contaminated with organic and inorganic pollutants such as the interstitial water in sediments. In many of these instances major modifications will be necessary. For work in anoxic basins, where hydrogen sulphide is present, most of the methods given here may be used provided that the hydrogen sulphide is first removed by acidifying the solutions to about pH 3 and bubbling vigorously with nitrogen gas until no more sulphide smell is apparent. Generally, quantities of certain substances such as ammonia and phosphate will be considerably higher in anoxic waters than in ordinary sea water. As mentioned in the Preface to our earlier works, we cannot claim that all the present methods are as free from defects as might be desirable, or that better techniques may not exist or become available soon. However, it is hoped they may prove of use to newcomers in the field or to institutions where marine chemistry is not of major importance but where a certain amount of analysis may have to be undertaken.