The Influence Of River-lake Relation Change On The Poyang Lake Sediments Nitrogen/Phosphorus Form And Release Risk

In recent years,with the reduction of water from Yangtze River,the relationbetween the Poyang Lake and Yangtze River has changed,resulting in the low waterlevel advanced and outcropped time prolonged,the prolonging sediments outcropptime will change the migration and transformation of nitrogen/phosphorus andincrease the release potential in the sediments of Poyang Lake.It’s well consided thatthe release of nitrogen/phosphorus promote eutrophication,the different migration andtransformation behavior in the sediment-water interface of nitrogen/phosphorus formsdues to its’ different active behavior,then affect the nitrogen/phosphorus releaserisk,Fourteen different elevation surface outcropped sediments of Poyang Lake werechoosed to studied the thermodynamics/kinetics release characteristics and thedifferent forms of nitrogen/phosphorus,tried to reveal the influence mechanisms ofthe water level changed in the River-Lake relation changed on thenitrogen/phosphorus release risk,meanwhile,tried to provided the theoretical basis forthe protection of the ecological environment and eutrophication of Poyang Lake.Theconclusions based on the above analysis are drawn:(1) The content of TN、TP、OM of Poyang Lake sediments showed the spatialdistribution that the distict of"Five Lake” into the Poyang Lake area werehigher,while the North and center Lake areas were lower,which may resulting fromthe different exogenous input of nitrogen/phosphorus pollution of these areas,thecontent of transferable nitrogen and inorganic/organic phosphorus forms showed thatFe-P＞Ca-P＞Ex-P＞De-P＞Oc-P＞Al-P,Nonlabile Po＞Moderately Po＞LabilePo,SOEF-N＞SAEF-N＞WAEF-N＞IEF-N.The content of TN、TP、OM wereincreased with the increasing elevation,means that the change of River-Lake relationwill increase the endogenous load of nitrogen/phosphorus,the prolonged outcropptime will increase the content of Ex-P、Fe-P、Or-P of inorganic phosphorus、NonlabilePo、Moderately Po、Labile Po of organic phosphorus, SOEF、IEF-N of thetransferable nitrogen,which were both accounts for the majority of thenitrogen/phosphorus levels,and were considered to be the labile nitrogen/phosphorus forms, suggesting that the River-Lake relation change will increase the bioavailabilityof nitrogen and phosphorus in the sediments of Poyang Lake, increase the releasepotential of nitrogen and phosphorus.(2) It’s showed that the adsorption/desorption equilibrium concentrations ofnitrogen/phosphorus in Poyang Lake sediments were much higher than the theeutrophication concentrations standard,means that the sediment will be the “source”of nitrogen/phosphorus at a long time even it reaches the eutrophicationconcentrations standard.The fitting parameters of the first-order kinetic equation ofNH4+-N、SRP showed that the release rate of NH4+-N、SRP were maximized at0~5min and reach a plateau at3h,with the increasing elevation, the maximal releasepotential and initial release rate of NH4+-N、SRP increased.So we can see that withthe water lever keeping lower,it’s bound to cause much more sediments have a longoutcrop time.As a result,the NH4+-N、SRP release quantity and eutrophication riskwill be increased.(3) The experiment of organic phosphorus bioavailability showed that the activemonester phosphate was the main factor of the H20-Po,while the diesterphosphate andphytate were much lower,NaOH-EDTA-P0was the main sorce of the organicphosphorus,phytate were main factors, NaOH-EDTA extracted water-solubilizingexhibited a low level> high water level variation,indicating that the exposedsediments will increase the bioavailability of organic phosphorus in Poyang Lakesediments,increasing the risk of eutrophication.