Trace metal diagenesis in sulfidic sediments: Insights from Chesapeake Bay

A non-steady state oxygenation event was recorded in the solid phase, with coincident solid phase enrichments in Fe, Mn, Ni, Cu and Co. Deeper enrichments in U and Mo likely reflect remobilization from the relict Fe and Mn peaks, downward diffusion into more reducing conditions, and subsequent immobilization. The absence of peaks in solid phase Re, Cr and Cd was indicative of their lack of association with Mn and Fe oxides and/or resistance of their respective authigenic phases to oxidation on these seasonal to yearly timescales. Relative changes within the solid phase profiles were captured using the acid digestion method for Fe, Ni and Co, and acid digestion concentrations were within 90% of the total concentration for Mn and Cu. The presence of excess pore water sulfide may have promoted the removal of trace metals from the detrital fraction resulting in the formation of authigenic sulfides that might become mobile during oxygenation events.