Trace elements: seawater to sediments

Abstract

Oceans represent a receptacle to the end products of a variety of processes operating at or near the surface of the earth. A knowledge of the sources, modes of transport and the deposition mechanism of the various constituents of sea water is of supreme importance - for understanding the various geophysical and cosmophysical processes, and even marine process themselves. Until today, only a qualitative or a semi-quantitative knowledge exists of the sources and important transport processes. Even here some of the important aspects of transport, viz., interaction of suspended matter with sea water and its regulatory effect on the concentrations of trace elements in sea water is poorly understood and hence grossly neglected in radiotracer applications or material budget estimates. The interaction of the solid phases with sea water occurs at all depths in the ocean, unlike the other transport processes, which take place only at interfaces. And it is primarily this reason why this study is in its infancy; mainly because of lack of simple experimental techniques which could bring to the laboratory sufficient quantities of "uncontaminated" oceanic suspended matter, filtered from few hundred tons of sea water. In this paper, we discuss the new techniques developed at TIFR partly in collaboration with J. Edmond and S. Stonecipher, for the collection of Gram quantities of oceanic particulates (extracted from hundreds of tons of sea water). Results of radiochemical analysis of these particulates are discussed in terms of particulate settling rates, disequilibrium in the case of natural radionuclides etc.