9312220 VANCAPPELLIN The major mechanism removing silicon from the oceans is the burial in sediments of biogenic silica remains. The burial flux of biogenic silica is controlled by production in surface waters, and by dissolution in the water column and surface sediments. To gain a better understanding of the dissolution process of biogenic silica, flow-through experiments will be performed with freshly collected sediment material and natural seawater. The experiments will address the role of pH, temperature, Na, Mg and Al on the dissolution process. The proposed research will also establish the evolution of the reactivity of biogenic silica as a function of depth/time in the sediments. The study will include dissolution experiments with the superficial fluff layer material, in order to quantify the amount of deposited biogenic silica that is recycled at the water-sediment interface. The experimentally determined kinetic rate laws, rate constants and solubilities will be included in an early diagenetic model for silica. The model will be used to test the response of (1) the flux of silicic acid from the sediments to the overlying water and (2) the burial flux of particulate silica, to variations of the silica deposition flux.
