Release of Toxic Metals via Oxidation of Authigenic Pyrite in Resuspended Sediments

During early diagenesis in anoxic sediments many reactive trace metals are coprecipitated with authigenic pyrite. Metals of potential environmental concern, such as As and Hg, can have in excess of 80% of their reactive fraction incorporated into authigenic pyrite within the top 10 cm of many sediments. Resuspension of sediment into overlying oxic waters can result in the oxidation of pyrite leading to release of the coprecipitated metals. Experimental studies indicate that from about 20% to 50% of the pyrite can oxidize in a day. The loss of trace metals from the pyrite fraction relative to pyrite-Fe is highly variable during the oxidation reaction, but generally is close to or greater than that of pyrite-Fe.