Elemental cycling in sediments underlying anoxic waters

6 Elemental cycling in sediments underlying anoxic waters 

Research in anoxic environments has suggested that some minor and trace elements are precipitated where free dissolved sulfide is present without undergoing a valency change, whereas others undergo a change in valency and are either more efficiently adsorbed onto solid surfaces under oxic or anoxic conditions or are precipitated under anoxic conditions. Therefore, the enrichment of many trace elements relative to their crustal abundances indicates only that the sediments accumulated under anoxic conditions, although not necessarily under anoxic bottom waters. However, Calvert and Pedersen (1993) demonstrated that I and Mn enrichments are reliable indicators of bottom 

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