Characteristics of organic phosphorus in different forms of lake sediments from east plain region.

Eighteen surface sediment samples taken from eight shallow lakes belonging to three different types in the eastern plain region of China were chosen to investigate their contents,forms and distribution characteristics of organic phosphorus(OP).The relationships between the OP fractions in sediments and their lake eutrophication were also discussed.The results showed that the contents of OP ranged from 65.2 to 539.2 mg /kg,accounting for 19.9% to 40.6% of w(TP),which were higher in the heavily polluted sediments than those in the lightly polluted ones.The main forms of OP in the sediments from the eight lakes were moderately labile organic phosphorus(MLOP) and nonlabile organic phosphorus(NLOP).Their contents varied greatly,and the rank order from different type of lakes was urban lakes farmings lake large lakes.The NLOP was the main organic phosphorus form for the sediments from the urban lakes and the farming lakes,the content of which accounted for above 50% of w(TP).However,the main organic phosphorus form of the sediments from the large natural lakes was the bioavailable organic phosphorus(LOP + MLOP),the content of which accounted for 54.6% ～ 61.6% of w(TP).It was suggested that the organic phosphorus distribution of the sediments was tightly connected with their lake pollution degrees and human activities.In addition,the contents of HCl-Po ranged from 10.5 to 200.9 mg /kg,varying greatly in different pollution degrees of lake sediments.The ratio w(HCl-Po) /w(Po) of the sediment was significantly associated with its water quality(P 0.01),and the contents of HCl-Po were significantly associated with the contents of TP,OP,LOP and MLOP in the sediments of those lakes(P 0.01).Hence,it was proven that the HCl-Po in lake sediment may be an important phosphorus source for the overlying water,and the ratio w(HCl-Po) /w(Po) in the sediment could reflect the level of lake eutrophication.