Phase associations of barium in marine sediments

Barium (Ba) is associated with various phases in marine sediments, including carbonates, organic matter, opal, ferromanganese oxyhydroxides, terrestrial silicates and other detrital material, and barite. Using samples representing sediments from a wide variety of sedimentary environments and export production regimes, we show that there is a considerable range in Ba concentrations associated with five operationally defined phases using a sequential extraction procedure (acetic acid, sodium hypochlorite, hydroxylamine hydrochlorite, hydrofluoric–nitric acid mixture, and a final residue dissolution). Distinct regional relationships between the relative abundance of Ba associated with different phases are observed. Since sedimentary Ba is widely used in algorithms to determine past export production, the variability in phase associations of sedimentary Ba shown here should be considered when reconstructing paleo-export productivity.