Trace metal transport across suboxic zones
A complex redox barrier is formed at the interface between oxic and anoxic zones in the environment. Three redox elements, Mn, Fe and S, are the key players forming this barrier. They precipitate at different redox levels and form a layered interface, with precipitated Mn at the oxic side and precipitated S at the anoxic side, with Fe in between. This layered zone regulates the flux of a number of metals across the interface, because of scavenging by solid Mn, Fe and S phases. The layered zone, the suboxic zone, has O2 and H2S concentrations below detection. It seems reasonable to assume that this is formed and maintained by redox-driven cycling of Mn.
The role of Mn for the cycling of redox-sensitive metals (Fe, Cr, Cu, Zn and U) will be studied, as well as how isotopic variations in these elements can be used to track metal transport across these layers. Samples will be collected from the pelagic suboxic zone in the Landsort Deep, Baltic Sea, from where background data is available, including Fe(II) measurements, and the area can be reached easily by boat.