VERTICAL DISTRIBUTION OF VARIOUS FORMS OF PHOSPHORUS IN THE SEDIMENTS OF DIANCHI LAKE, CHINA

The phosphorus fractions of 15 core sediment samples collected from the Dianchi Lake were analysed, and characters of vertical distribution were discussed. In present study, the sediment phosphorus was fractioned into exchangeable phosphorus (Exch-P), aluminum bound phosphorus (Al-P), iron bound phosphorus (Fe-P), calcium bound phosphorus (Ca-P), occlude Al-P, occlude Fe-P, inorganic phosphorus (IP) and total phosphorus (TP). The results showed that the TP concentrations in the sediment ranged from 701.97 to 2868.61 mg.kg(-1), and IP was the main fraction of TP, ranging from 491.64 to 2254.73 mg.kg(-1). Simultaneously, the Ca-P was the main fraction of IF, ranging from 200.64 to 1381.77 mg.kg(-1). It indicated that the water body was much more eutrophic. The vertical distribution of different samples was distinguishing. The relationships between TP concentration and Fe-P, Ca-P, occlude Fe-P and Org-P concentrations were significant. TP and Fe-P showed obviously vertical and spatial variation. In some samples, the high TP and Fe-P concentrations in surface 0-20 cm showed the increasing P inputs in the recent 50 years. The vertical distribution indicated that the P concentration was related to the humanity with a certain extent, moreover, the internal source pollution played an important role in the eutrophication of the Dianchi Lake, and some sewage interception projects were resultful. The amounts of P released from the sediments had positive correlations with TP contents. It indicates that the heavily polluted sediments may have the high risk of P release.