Spatial distribution characteristics of phosphorus forms in sediment of Lake Hongfeng,Guizhou Province

Lake Hongfeng is a man-made deep lake.Phosphorus of sediment samples that were collected from representative six water areas were analyzed.Water temperature and dissolved oxygen were investigated four times in the field by multi-parameter water quality observation analyzer YSI.The results showed that total phosphorus in sediment was generally high.The average value of total phosphorus in surface sediment was more than 1500 mg/kg,significantly higher than that in the bottom sediments.NaOH-SRP and rest-P were the main forms of phosphorus in sediment.NH4Cl-P,BD-P and HCl-P contents decreased with depth,and rest-P contents were stabile in vertical.Human activities(e.g.chemical waste water and artificial fish) greatly increased NaOH-SRP contents in sediment.Temperature of bottom water was between 14.5-23.5℃,and the maximum temperature differences was 9.9℃ in different seasons.The bottom water was seasonal anoxic or anaerobic,which may result in changes of sediment phosphorus forms.Risk of endogenous phosphorus release increased due to anoxic condition of sediment-water interface in deep lake.