Study on Novel Structures Phosphorus Sorption Capacity of Surficial Sediment in Dongping Lake and Risk Assessment of Potential Phosphorus Release

Phosphorus sorption capacity of the surficial sediments are estimated by the phosphorus sorption index (PSI) and the degree of phosphorus saturation (DPS) of the sediments in the Dongping Lake, China. In addition, the risk of potential phosphorus release was also analyzed. The results showed that PSI gradually increased from the middle and the east of the lake to the north and the south, which was fan-shaped. However, the variation tendency of DPS was contray to this of PSI. PSI was very significantly and positively correlated to iron (FeOX) extracted from sediment by ammonium oxalate. DPS was significantly and positively correlated to phosphorus (POX) extracted from sediment by ammonium oxalate. Additionally, the analysis of the phosphorus release risk index (RRI) indicated that the Dongping Lake might be in high potential eutrophication risk due to the release of phosphorus from the surfacial sediments.

Phosphorus availability in soils subjected to short periods of flooding and drying

The effects of flooding and drying on the availability of original soil phosphorus, phosphorus added before flooding and phosphorus added after drying were studied. In four soils high in organic carbon and reducible iron, 2 or more days of flooding (at 25�C) caused the immobilization of phosphorus added after drying. Four or more days of flooding caused immobilization of original soil phosphorus. Phosphorus applied before the flooding period was immobilized to a greater degree than phosphorus applied after drying in a soil rich in organic carbon and reducible iron. In a soil low in these, phosphorus applied before flooding was immobilized, but phosphorus applied after drying was not. Changes in soil extractable iron and phosphorus, and in phosphorus sorption index, caused by flooding and drying, were consistent with immobilization of phosphorus added after flooding by a surface reaction, and the immobilization of phosphorus present during flooding by occlusion of phosphorus with iron(III) hydrous oxide, or by formation of iron(III) phosphate.