Comparative environmental chemistries of metals and metalloids

Abstract

A number of factors have given rise to the explosive expansion in knowledge over the past decade about the behaviours of metals and metalloids in the environment. First of all, there has been a marked increase in the number of investigators in all phases of geochemistry. Secondly, there have been major improvements in analytical and sampling techniques such that even very low concentrations of metals and metalloids in atmospheric, solid or liquid samples can be assayed accurately without contamination. Where microgram quantities and micromolar solutions were commonly discussed twenty years ago, today it is not unusual to investigate the systematic chemistries of metals in the picomolar concentrations in natural waters. Mounting concerns about damage to the environment through the inadvertent or deliberate entry of metals and metalloids have stimulated many pollution-type studies. Finally, there is developing a series of laboratory and field techniques that allow the identification of species of metals and metalloids in natural systems. But I suspect that the increase in knowledge about the geochemistries of metals and metalloids has not paralleled the increase in efforts in their study. One contributing argument to substantiate this mood is that often only one or two elements are analysed per samplethe analyses more determined by the availability of instruments or by the limitations of the technique than by the problems that might be solved. I argue that a return to a classical geochemical approach wherein groups of elements that are related through their location in the periodic table are analysed in samples to develop comparative geochemistries will again be a rewarding strategy for both basic and pollution-directed environmental investigations. In the pioneering texts of Goldschmidt (1954) and Rankama & Sahama (1950) the manner and occurrence of the elements in our surroundings were treated systematically, often through considerations of their places in the periodic table. Although interpretations of their geochemistries were usually based upon the vertical rows of the periodic table, sometimes horizontal Professor Goldberg is Senior Scientist at the Scripps Institution of Oceanography at La Jolla, California, and is a noted authority on marine pollution affairs. His editorial in the Marine Pollution Bulletin stimulated the world-wide Mussel Watch Program.