The adsorption of saxitoxin to clays and sediments in fresh and saline waters.

The adsorption of saxitoxin to Na- and Ca-montmorillonite, kaolin (crystalline and amorphous), kaolinite, Bread and Butter Creek sediment (an estuarine tidal creek), Gulf of Mexico sediment, and Santa Barbara Basin sediment in deionized water and 32 per thousand salinity simulated seawater (Instant Ocean) is reported. Adsorption was partially reversible for all cases and best described using a Freundlich isotherm. The corresponding Freundlich constants (K(F)) ranged from 8.83 x 10(3)micromol/kg to 6.76 x 10(4)micromol/kg for freshwater and 4.73 x 10(3)micromol/kg-1.11 x 10(4)micromol/kg for seawater. There is a positive linear correlation seen between the K(F) values and the cation-exchange capacity of the adsorbents. The release of saxitoxin from previously equilibrated adsorbents was determined in freshwater (0-18%) and seawater (4-53%).