Molecular Weight Distribution of Organic Phosphorus in Lake Sediments

Abstract

Total P, oraganic P and fractionated inorganic P were determined in a core sample of 130cm depth collected from Lake Suwa. Total P, aluminum P and iron P were enriched in the surface sediment. Organic P in the core sample ranged from 0.18 to 0.39 mg·g^-1 and its percentage to total P ranged from 12.3 to 18.8%. The change of oraganic P with the core depth was closely related to that of organic C. Organic P was fractionated into three fractions through a column of Sephadex G-75. In the surface sediment the percentages of organic P in G-75-I (MW>50, 000), G-75-II (MW=1, 00050, 000) and G-75-III (MW<1, 000) were 32.9, 38.7 and 28.4%, respectively. The amount of organic P decreased with the core depth in G-75-II and G-75-III, while it was unchanged in G-75-I. Organic P was separated into humic acid and fulvic acid fractions and the molecular weight distributions of the fractions were determined. It was suggested that organic P in lake sediments was stable in the high molecular weight fraction.