Abstract: In order to investigate cycling and burial of phosphorus and nitrogen in Chaohu Lake,the sequential extraction method was used to measure different forms of phosphorus and nitrogen in sediments of the lake.It was found that total P in the sediment ranged from(0.1110.655) g·kg^-1,averaging 0.358 g·kg^-1,and was composed mainly of inorganic P(65%-72%),dominated with Fe-bound P.Total N in the sediment ranged from 0.220-0.922 g·kg^-1,averaging(0.532) g·kg^-1,and was composed mainly of organic nitrogen(94.7%).All these indices signify that Chaohu Lake is in the state of cleanness and almost cleanness.The very close linear relations between organic matter,total phosphorus and total nitrogen in the sediments indicate the nutrients in Chaohu Lake come from the same source.The mean TOC/N ratio of the sediment suggests that the organic matter in Chaohu Lake originates from land.

Key words: phosphorus, nitrogen, organic matter, sediment, Chaohu Lake