Sediment cores were obtained from 15 lake stations representing the three major basins and the Inshore Zone of Lake Ontario. Cores were sectioned for characterization of the surface sediments according to inorganic P chemical mobility. Physical mobility was characterized by measurement of P release from intact cores incubated under controlled laboratory conditions. The proportions of potentially chemically mobile inorganic P were usually high (30 to 60%) in the central basin sediments and low (2 to 8%) for the inshore zone sediments. Although the amounts of inorganic P desorbed after three successive equilibrations (in .1M NaCl) of Lake Ontario sediments represented only 3 to 17% of the potentially mobile inorganic P, sufficient inorganic P was desorbed to restore a large part of the original interstitial inorganic P concentrations. Based on an inorganic P flux of 0.2 mg/sqm/day, the estimated annual contribution of inorganic P to Lake Ontario water is equal to about 10% of the external P loading.

"February 1975." "Research conducted by the University of Wisconsin, Madison, Water Chemistry Program and Soils Department." Includes bibliographical references (pages 48-51). U.S. Environmental Protection Agency Contract No. Contract Number: #800609, Program Element 1BA026, ROAP/Task No. 21 AKP/008.