DATA OF GEOCHEMISTRY 



CHEMICAL COMPOSITION OF RIVERS AND LAKES 



By Daniel A. Livingstone 



DUKE UNIVERSITY, DURHAM, NORTH CAROLINA 



ABSTRACT 



This paper is a compilation of representative chemical data, 

 many previously unpublished, for the lake and river waters of 

 the world. The rate of chemical denudation for the continents 

 of the world ranges from 6 long tons per square mile for Aus- 

 tralia to 110 long tons per square mile for Europe. The rivers 

 of the world deliver 3.9 billion tons of dissolved material to 

 the sea each year, and the average concentration of the important 

 constituents in parts per million is: bicarbonate 58.4, sulfate 

 11.2, chloride 7.8, nitrate 1.0, calcium 15.0, magnesium 4.1, 

 sodium 6.3, potassium, 2.3, iron 0.67, and silica 13.1, for a total 

 of 120 ppm of dissolved solids. Although these 10 constituents 

 account for most of the dissolved material, all but 37 of the 

 naturally occurring elements have been detected in lake or river 

 water. The principal gaps in geochemical data for lakes and 

 rivers are long-term downstream averages for the general com- 

 position of large tropical rivers and trace-element analyses for 

 large rivers everywhere. 



INTRODUCTION 



Atmospheric precipitation is the principal source of 

 the water substance that makes up lakes and rivers on 

 the earth's surface. This is not pure water, but is in 

 equilibrium with atmospheric gases, and in addition 

 contains some dissolved and suspended mineral matter, 

 part of which is the original nucleus of crystal or droplet 

 condensation, and part taken up by the crystal or 

 droplet during its passage through the atmosphere. 



Although a headwater stream or a lake with a small 

 catchment area, particularly in regions of relatively 

 insoluble rocks, may contain water that is almost 

 identical in chemical composition with rain water, it is 

 usual for lakes and rivers to contain much more sus- 

 pended and dissolved material than this. As water 

 percolates through the soil, it attacks the mineral 

 constituents physically and chemically, leaching out 

 the more soluble fractions. This water ultimately 

 finds its way into rivers with more or less delay in basins 

 filled with standing water, while evaporation from the 

 water surface tends to increase the salt concentration in 

 the water. More salts may be leached out of the 



643S62 — 63 2 



suspended material in the stream, or, alternatively, 

 salts may be removed from the water by the suspended 

 or bottom material through a variety of sorptive 

 processes. Organisms living in the water may take up 

 dissolved material, particularly nutrients such as 

 phosphate, nitrate, and silicate (Lund, 1950) that tend 

 to be in short supply, and drastically reduce its con- 

 centration in the water. At intervals large numbers of 

 these organisms may die, suddenly releasing their con- 

 centrates into the waters around them, and producing 

 a local and temporary concentration of the elements 

 characteristic of protoplasm. 



Because of these changes, a river or lake is a complex 

 dynamic system. Its chemistry cannot be adequately 

 described in terms of static analysis, but must include 

 some information about the potentialities of the system 

 as well as information about the composition of its 

 water at a particular moment. Investigation of these 

 chemical potentialities is much more time consuming 

 than chemical analysis of a single water sample and for 

 some practical purposes it is not necessary, but the 

 serious shortage of attempts to measure it introduces 

 grave uncertainties into the geochemical data for this 

 part of the biosphere. 



ACKNOWLEDGMENTS 



This review was prepared during tenure of three 

 National Science Foundation grants and during part- 

 time employment with the U.S. Geological Survey. 



A very large part of the basic data for lakes and rivers 

 lies in unpublished files and reports. In searching for 

 this material I had the aid of water chemists in many 

 parts of the world and of a large part of the world's 

 governmental quality-of-water agencies. I am very 

 grateful for the help they freely and unstintingly gave. 

 An especial debt of gratitude is due to the following 

 people and organizations who have provided unpub- 

 lished analyses for inclusion in this volume: Dr. Eville 



Gl 



