Effects Of Hydrostatic Pressure And Dissolved Oxygen On Phosphorus Cycle Transformation Genes In Reservoir Sediments And Modified Zeolite Remediation

The release of phosphorus in the sediments of reservoir lakes is a key trigger for the eutrophication of water bodies.In this paper,the dissolved oxygen and hydrostatic pressure are used as control conditions to simulate the water-sediment multiphase inter face of the Jinhe Reservoir in Heihe.The effects of basic physicochemical properties,alkaline and acid phosphatase activities,ppk(polyphosphoric acid),phoD(alkaline pho sphatase gene),gcd(glucose dehydrogenase gene),pqqc(pyrroloquinoline quinone gen e),and microbial community structure of phosphorus in sediments were discussed,The in-situ stabilization of endogenous phosphorus at the interface of modified zeolite was investigated.The study draws the following conclusions:Under different dissolved oxygen conditions,as time goes by(0-60 days),TP(tot al phosphorus)in the sediment remains relatively stable over time,OP(organic phosp horus)content decreases with time,and has a higher content under high DO(dissolve d oxygen).The increase of iron-aluminum-bound phosphorus is accompanied by the de crease of calcium-bound phosphorus,and calcium-bound phosphorus is partially convert ed to iron-aluminum-bound phosphorus.The differences between ALP(alkaline phosph atase),ACP(acid phosphatase)and chlorophyll are always significant.The abundance o f phoD gene in sediment was positively correlated with alkaline phosphatase activity.When the test runs to the second stage,DO and phoD abundance are positively correl ated.Alkaline phosphatase activity is regulated by the phoD gene.At the same time,with the expression of phoD,the conversion of inorganic phosphorus will be accelerat ed,and the sediment will release more phosphorus into the water body;ppk gene and DO,calcium-bound phosphorus,alkaline phosphatase,Chlorophyll content was signifi cantly positively correlated.With the increase of dissolved oxygen,the combined actio n of the ppk gene,phoD geneand alkaline phosphatase accelerates the transformation o f inorganic phosphorus;the expression of the pqqc gene will promote the occurrence of iron-aluminum combined phosphorus,and at the same time accelerate the transform ation of inorganic phosphorus,and finally Promote the release of phosphorus in the se diment.The dominant bacterialphyla of phoD and ppk-type microorganisms are Actino bacteria(Proteobacteria)and Proteobacteria(Proteobacteria).The predominant bacterial phylum of gcd-type microorganisms is Gemmatimonadetes(Bacillus).Under different hydrostatic pressure conditions,hydrostatic pressure had extremelys ignificant effects on TP,OP,iron-aluminum-bound phosphorus,calcium-bound phosphor us,alkaline phosphatase,acid phosphatase,ammonia nitrogen,and pH;Significant effe ct,no significant effect on IP,soluble orthophosphorus,phoD,ppk genes.High hydrost atic pressure increases the activity of alkaline phosphatase and acid phosphatase,and p romotes the release of nitrogen and phosphorus.The phoD gene will promote the con version of IP,iron and aluminum combined phosphorus,and inhibit ammonia nitrogenf rom entering the water body.The expression of ppk gene is negatively correlated with pqqc gene,and the two inhibit each other.When the hydrostatic pressure drops,it pro motes the expression of the pqqc gene,while inhibiting the activity of alkaline phosph atase and acid phosphatase,reducing the TP content in the sediment,so that more ph osphorus enters the water body.In the zeolite modification experiment,the zeolite was screened and modified by thermal modification,alkali modification,acid-thermal modification,and alkali-thermal modification.Mordenite and phosphorus locking agent have better binding ability.Amo ng the four lanthanum modification experiments,the relative content of La2O3 was th e highest after alkali-thermal modification,reaching 2.16%.The amount of phosphorus adsorbed by lanthanum-modified mordenite was 4.13 times higher than that before un modified.In the simulation experiment of water-sediment in-situ stabilization and repair,under anaerobic conditions,the phosphorus concentration decreased by 68%and the a mmonia nitrogen concentration decreased by 32%after the addition of zeolite.Under aerobic conditions,after the addition of zeolite,the phosphorus concentration decreased by 50%and the ammonia nitrogen concentration decreased by 15.6%.