10.0 TRACE METALS 



By K. K. Turekian 

 Department of Geology and Geophysics 

 Yale University, New Haven, Connecticut 



INTRODUCTION 



The mobilization of many trace elements is effected by natural 

 processes acting at the Earth's surface. Weathering results in the 

 alteration of rocks with the release and redistribution of many of the 

 trace elements in the process. Some part of this released load enters 

 the groundwater system in solution and ultimately makes its way to the 

 oceans via streams. Another part becomes incorporated in the soil 

 profile in association with the organic fraction. This material also 

 makes its way to the sea as the result of erosion. During transport the 

 different components of this entourage are influenced by the chemical- 

 physical processes acting in streams and in the estuarine system result- 

 ing in the distribution of the trace metals that we observe in the estu- 

 ary. Upon reaching the estuarine zone the metals do not commonly become 

 passive but can undergo a flux and redistribution through natural sedi- 

 mentation-erosion processes, chemical mobilization, or incorporation 

 into biota. 



Man has added to the natural trace-metal load by injecting 

 materials, resulting from his activities, into every part of the pathway. 

 Atmospheric transport deposits alien nuclides on to the surface invading 

 the soil profiles as well as the estuarine or sea surface. Metal- 

 bearing effluent from industries imprints the streams and groundwater 

 with contaminants. Domestic sewage is funneled through treatment plants, 

 but not all metals or other toxic materials are completely isolated. 



The consequences of these human perturbations on the natural 

 trace-metal regime of the coastal system are readily observed in the 

 biota, water and sediments. Elevated metal levels have been well documen- 

 ted. The response, however, has not been the same everywhere and the 

 potential damage to the environment cannot always be directly correlated 



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