Carbonyl sulfide hydrolysis as a source of hydrogen sulfide in open ocean seawater

Abstract

Two independent lines of evidence suggest that the hydrogen sulfides (H2S, SH−, S2−) are present in open surface seawater at pico to nanomolar levels. 1) Such concentrations are calculated for a chemical steady state involving carbonyl sulfide hydrolysis as source, followed by oxidative removal. 2) Although it is not yet certain that measurements of gaseous H2S over the open ocean are reliable, they require aqueous sulfide concentrations in this range in order to support sea‐to‐air flux. If pico to nanomolar of the hydrogen sulfides are included in standard equilibrium models of seawater complexation chemistry, several trace metals speciate predominantly as sulfide complexes and are supersaturated with respect to their solid sulfides. This supersaturation argues for solubilization of the metals through other unexpected complexes, perhaps involving reduced sulfur ligands associated with dissolved organics, or even intermediates along the hydrogen sulfide oxidation chain.