Metal chelation in sedimentary systems

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Abstract
An aqueous suspension of clay, dolomite, quartz and organic matter was sedimentd through a saline solution containing trace amounts of Cu and Zn and acccumulated on an organic-rich layer where sulfide was being generated by sulfate-reducing bacteria. A control system was set up in which the organic matter was omitted and the sulfide provided by diffusion of a sodium sulfide solution from beneath the sediments. In the organic system the Cu and Zn were separated and fixed in different sedimentary layers; in the control system they precipitated together. Metal distributions in the formef system indicated that Cu forms soluble metal-organic complexes that keep the Cu in solution in the presence of sulfide. Zn also forms metal-organic complexes, but these are apparently not resistant to sorption and precipitation processes.