Characterization of Organic Phosphorus in Lake Sediments by Sequential Fractionation and Enzymatic Hydrolysis

Abstract

The role of sediment-bound organic phosphorus (P<sub>o</sub>) on lake eutrophication was studied using sequential extraction and enzymatic hydrolysis by collecting sediments from Dianchi Lake, China. Bioavailable P<sub>o</sub> species including labile monoester P, diester P, and phytate-like P were identified in the sequential extractions by H<sub>2</sub>O, NaHCO<sub>3</sub>, and NaOH. For the H<sub>2</sub>O–P<sub>o</sub>, 36.7% (average) was labile monoester P, 14.8% was diester P, and 69.9% was phytate-like P. In NaHCO<sub>3</sub>–P<sub>o</sub>, 19.9% was labile monoester P, 17.5% was diester P, and 58.8% was phytate-like P. For NaOH–P<sub>o</sub>, 25.6% was labile monoester P, 7.9% was diester P, and 35.9% was phytate-like P. Labile monoester P was active to support growth of algae to form blooms. Diester P mainly distributed in labile H<sub>2</sub>O and NaHCO<sub>3</sub> fractions was readily available to cyanobacteria. Phytate-like P represents a major portion of the P<sub>o</sub> in the NaOH fractions, also in the more labile H<sub>2</sub>O and NaHCO<sub>3</sub> fractions. Based on results of sequential extraction of P<sub>o</sub> and enzymatic hydrolysis, lability and bioavailability was in decreasing order as follows: H<sub>2</sub>O–P<sub>o</sub> > NaHCO<sub>3</sub>–P<sub>o</sub> > NaOH–P<sub>o</sub>, and bioavailable P<sub>o</sub> accounted for only 12.1–27.2% of total P<sub>o</sub> in sediments. These results suggest that the biogeochemical cycle of bioavailable P<sub>o</sub> might play an important role in maintaining the eutrophic status of lakes

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