Chemical composition and thermodynamic properties of diatom valves as applied to the dissolution and sedimentation of biogenic silica in Lake Baikal

Thermodynamic indices of biogenic silica have been calculated on the basis of data of X-ray spectral electron probing and the chemical composition of diatom valves. Application of these new data to a physicochemical model for Lake Baikal allowed us to put forward a new concept of biogenic-silica dis solution, which explains the constant concentration of silicium in the Baik al water, The data also suggest that the conservation of biogenic silica in bottom sediments depends on the amorphous state of SiO2 making up the valv e, Preliminary data on the involvement of biogenic opal in diagenesis of th e bottom sediments are reported.