Characteristics And Bioavailability Of Organic Phosphorus From Different Sources Of Dianchi Lake

Eutrophication of Dianchi Lake has been serious over last few years,biogeochemical cycles of organic phosphorus from different sources may be a keyfactor in maintaining eutrophication of Dianchi Lake. Enzymatic hydrolysis isinvolved in the biogeochemical process of organic phosphorus in aquatic ecosystems.In this paper, the enzymatic hydrolysis technology has used to characterizebioavailability of organic phosphorus from different sources (Lake,inflowing riversand rainfall) of Dianchi Lake, attempting to provide a scientific evidence forunderstanding and evaluating phosphorus bioavailability of Dianchi Lake.The conclusions based on the article are drawn:(1) Dissolved organic phosphorus (DOP) represented a major part of dissolvedtotal phosphorus (DTP) from different sources (Lake,inflowing rivers and rainfall).The concentrations of enzymatically hydrolysable phosphorus(EHP) from differentsources ranged from not detectable(nd)-0.058,nd-0.673and nd-0.031mg/L,and thepercentage of enzymatically hydrolysable DOP (EHP/DOP) from were relatively high.DOP from different sources showed evident characteristic of spatial and temporaldistribution and the bioavailability of DOP from Lake Dianchi, inflowing rivers andrainfall declined in turn.Labile monoester P and phytate-like P represented primaryportions of EHP in Dianchi Lake,whereas,EHP from inflowing rivers and rainfallwere composed mainly of Labile monoester P,especially for rainfall which hadrelatively low concentrations of diester P and phytate-like P. EHP from differentsources represented a source of available P of equivalent magnitude to SRP, so EHPand SRP keep eutrophication of Dianchi Lake together.(2) The inorganic phosphorus represented primary portions of extractablephosphorus of sediments in Dianchi Lake. The rank of order of organicphosphorusfractionation in sediments of Dianchi Lake was NaOH-Po> NaHCO3-Po>H2O-Po>HCl-Po.The vertical distribution of NaOH-Po, NaHCO3-Poand H2O-Powithrelativelyhigh mobility showed the trends: the topper layer>middle layer>bottomlayer.The EHP content of NaOH-Po, NaHCO3-Poand H2O-Powere0.11-5.93, 0-45.32and0-107.11mg/kg respectively. The EHP content of different organicphosphorus species followed the order: NaOH-Po>NaHCO3-Po>H2O-Po, with thetrends of the distribution: the topper layer>middle layer>bottom layer. Labilemonoester P represented primary portions of EHP in sediments of Dianchi Lake,diester P and phytate like-P coming second.The bioavailability of organic phosphorusof different depth keeped the order: the topper layer>middle layer>bottom layer.EHP were an considerable source of the bioavailable phosphorus of sediments inDianchi Lake.The biogeochemical cycle of EHP might paly an important role inmaintaining the eutrophication of Dianchi Lake.(3) The content of organic phosphorus from different sources followed the order:sediments of Dianchi Lake (416.50mg/kg)>waters of inflowing rivers (196.3mg/kg)>rainfall (36.85mg/kg)> waters of Dianchi Lake (27.10mg/kg), their EHP contentaccording to the following sequences: waters of inflowing rivers (63.70mg/kg)>sediments of Dianchi Lake (49.35mg/kg)>waters of Dianchi Lake (17.31mg/kg)>rainfall (10.50mg/kg). The bioavailability of organic phosphorus from differentsources keeped the order: waters of Dianchi Lake>waters of inflowing rivers>rainfall>sediments of Dianchi Lake. Treatments for Dianchi Lake should consider theeffects of different phosphorus species from different sources for the water quality inthe overall watersheds perspective, especially reinforcing the management for thepollution of inflowing rivers.