Dissolution kinetics of biogenic silica and the recalculated silicon balance of the East China Sea

Abstract

We conducted field observations in the East China Sea (ECS) in 2010 and 2011 to determine the content and dissolution dynamics of bSiO2 in sediments of the ECS. The influencing factors on bSiO2 dissolution were investigated, and the regional silicon budget was recalculated. The sediment bSiO2 content in the ECS varied from 143 to 583 μmol g−1. The burial flux of bSiO2 ranged from 0.11 to 19 mol m−2 yr−1 and gradually decreased eastward offshore from within and north of the Changjiang River. Continuous flow experiments showed that the solubility of bSiO2 in surface sediments varied from 213 to 357 μM-Si, and the dissolution rate constant of bSiO2 was 14.9–56.6 nmol g−1 h−1; both ranges are lower than those of other marginal seas, such as the Arabian and Scotia Seas. The release of soluble aluminum from lithogenic minerals was suggested to influence the pore water build-up of dissolved silica in the ECS. The silicon budget of the ECS was recalculated based on up-to-date research. Due to the low dissolution rate constant and high sediment accumulation rate, sediment bSiO2 in the ECS is well preserved, with a burial efficiency of 81%; this accounts for 9.9% of the global burial rate and is significantly higher than that of the Yellow Sea and the global ocean average.