Distribution and dissolution kinetics of biogenic silica in sediments of the northern South China Sea

Abstract

The dissolution efficiency of sedssimentary biogenic silica (bSiO2) dramatically affects the regeneration of dissolved silicic acid (dSi) at the sediment-water interface, which is a crucial pathway to maintain Si balance and silicic productivity growth in marine environments. We conducted wet alkaline leach and flow-through experiments to explore the dissolution behaviors of sedimentary bSiO2 in the northern South China Sea (NSCS), one of the largest marginal sea continental shelves. The bSiO2 contents of surface sediments were 0.64 - 2.06%, with an average of 1.04 ± 0.35%, varying with isobath water depth. The solubility of bSiO2 in surface sediments ranged from 227 μmol L-1 to 519 μmol L-1, and the dissolution rate constants varied from 0.67 to 1.53 yr-1 under specific conditions in lab incubation. The correlation between the biogenic materials (bSiO2, OC, and TN) revealed a different preservation pattern of bSiO2 in finer (Φ > ~ 5.5) and coarser (Φ