Biogenic silica dissolution in seawater - in vitro chemical kinetics

The experimental and mechanistic approaches available for the study of the kinetics of in vitro biogenic silica dissolution are synthesised to provide rigorous guidance for future investigation. Batch and flow-through reactor s are discussed, as are the four mechanisms which have been proposed previo usly within the marine domain. In recognition of success with similar probl ems in mineral weathering and hydrometallurgy, the applicability of the Act ivated Complex Theory is also considered. Full mathematical derivations are presented for the mechanisms before they are evaluated according to contem porary needs. At each stage the problems inherent in fitting mathematical m odels to experimental data are highlighted. The decrease in reaction rate w ith time observed in batch reactors is discussed in terms of both the appro ach towards saturation and decrease in surface area of the dissolving frust ules. In appreciating this distinction, optimum combinations of experimenta l design are suggested for mimicking silica dissolution in either the water column or sediment. The role of organic frustule components, micro-organis ms and faecal pellets in the dissolution process are discussed. (C) 2001 El sevier Science Ltd. All rights reserved.