Spatial distribution, fractions, and potential release of sediment phosphorus in the Hongfeng Reservoir, southwest China

Abstract

We investigated the spatial distributions of total phosphorus (P) and its fractions in the sediments from Hongfeng Reservoir, the largest man-made water body in southwest China, to reveal P sources to the reservoir and its pollution history. We sectioned sediment cores and measured P species concentrations, which increased progressively from relatively low concentrations at a depth of 20–30 cm to higher concentrations in upper sediment layers, reflecting an increase in P input that accompanied anthropogenic influences. P bound to metal oxides (NaOH-SRP) was the largest component of P in most core profiles, accounting for 34.6–67.2% of total P. The Yangchang River is the primary external P source to the reservoir and should be the focus of remediation efforts in the future. A batch P release experiment conducted using sediment cores showed that sediment P release was mainly caused by the transformation and/or desorption of NaOH–P and Residual–P under high temperature and low oxygen conditions. Large P release from sediments could affect the water quality of the reservoir in the future. Detailed knowledge of in situ microscale changes at the sediment–water interface is required to understand the migration of P fractions in the sediments.