Measurement of exchangeable inorganic phosphate in lake sediments.

H The amounts of isotopically exchangeable inorganic phosphate in a range of Wisconsin lake sediments were measured in two contrasting (longand short-term) equilibration systems. The systems differed in equilibration times, oxidation-reduction conditions, and the degree of agitation. Levels of total exchangeable inorganic P were similar for the two systems, indicating that the simplified short-term equilibration method was suitable for routine measurements of exchangeable inorganic P. Differences between the two systems in the distribution of exchangeable P between the solid and solution phases were apparently related to differences in oxidation-reduction conditions. Exchangeable inorganic P ranged from 18-65% of the total inorganic P in the sediments investigated.