Vertical variation of phosphorus forms in surface sediments from Wuli Bay,Taihu Lake,China

In order to investigate the cycling of phosphorus in the Taihu Lake, a sequential extraction technique was used to separate different phosphorus forms in surficial sediments from the Wuli Bay of the Taihu Lake. The concentrations of total P are high in the sediments, with an average of {2.80} mg·g+{-1}, and a variation range between {4.02} and {2.05} mg·g+{-1}. Total P is composed mainly of inorganic P (70%-90%), a large portion (75%-85%) of which lies in the CDB-extractable iron oxide phase. The low Fe/P atomic ratios ({2.0}-{5.3}) indicate that the Fe compounds extracted with CDB have a lower proportion of relatively crystalline phases in all samples, and that the absorption between iron and phosphorus has probably reached certain equilibrium. Organic C/N atomic ratios ({8.8}-{10.6}) for most of the samples are lower, which suggests a lacustrine authigenic source of organic matter in the sediments. Moreover, organic C/P atomic ratios (135-320) are usually higher than the Redfield ratio (106∶1), showing that the organic phosphorus had been preferentially released via organic matter degradation during the early diagenesis process.