Phosphorus species and distribution characteristics in sediment of Nansi Lake.

By the method of sequential extraction,various species of phosphorus were extracted and determined on each sediment samples in the downstream Nansi Lake and its inflows.Distribution characteristics of phosphorus species in surface sediments and sediment cores were analysed.There was no significant regularity in the horizontal distribution of phosphorus species,but there existed obvious variances in contents.Bio-available phosphorus(BA-P),sum of exchangeable phosphorus(Ex-P),Al bound phosphorus(Al-P) and iron bound phosphorus(Fe-P),accounted for 41%～65% of the total extracted phosphorus in the sediments,suggesting a high bio-availability in the surface sedimentary phosphorus.There was large content of bio-available phosphorus in sediment cores,which was mainly consisted of Ex-P and Fe-P but less Al-P.The contents of occlude phosphorus(Oc-P),auto-calcium-bound phosphorus(Aca-P),debris phosphorus(De-P) and organic phosphorus(Or-P) were quite stable in sediment cores comparatively.Inorganic phosphorus was the overwhelmingly dominant species in both surface sediments and sediment cores,indicated that sediments in Nansi Lake was mainly deposited by inorganic phase.