Early diagenesis of phosphorus in recent sediments of the estuary and the gulf of St Lawrence

Abstract

A sequential extraction method is used to differentiate between four phases of particulate phosphorus in recent sediment and in suspended particulate matter of the estuary and the gulf of St Lawrence. The four P phases are extracted in the following order: (1) the exchangeable P fraction (P_ex) after washing the solid matter in ammonium acetate, (2) the inorganic P fraction adsorbed onto iron-oxides (P_cdb) using a citrate-dithionite-bicarbonate buffered reagent (‘cdb’), (3) the apatite P fraction (P_ap) dissolved in HCl, and (4) the organic P fraction (P_org) released after ashing and HCl treatment. The simultaneaous determination of the atomic ratio of the iron oxyhydroxide (Fe_cdb) to the _Pcdb serves as an indicator of the level of orthophosphate adsorption in various redox conditions of the environment.