Fate Of Phosphorus In Sediments Of Jinpen Reservoir And Its In-situ Control Using Water Lifting Aerator

In order to understand the transformation and distribution characteristic of phosphorus in the sediments and the effect of water lifting aerator on the control of phosphorus released from Heihe Jinpen Reservoir,the physical and chemical properties of the overlying water body,interstitial water,sediment particles(moisture content,particle size,organic matter,etc),and the phosphorus content and occurrence of the sediments were monitored for one year.The main researches are as follows:(1)the occurrence forms and distribution characteristics of phosphorus in sediments of the Jinpen reservoir;(1)the seasonal changes and the rules of migration and transformation of phosphorus in surface sediments;the control of phosphorus in Jinpen reservoir by water lifting aerator.The main conclusions are as follows:(1)The organic matter content in surface sediments of Jinpen reservoir was45.12±0.16 mg/g,and the protein content was 4.85±0.05 mg/g.All of the soluble organic matter were humus-like,and the sediments were mainly silt(the particle size is0.002~0.05 mm).The content of total phosphorus in surface sediments was 724~780mg/kg,and the content of organic phosphorus(OP)accounts for 17~26%of total phosphorus.The order of the percentage of total phosphorus in each form of phosphorus with depth changes was:Ca-P>NaOH-P>Residue-phosphorus>BD-P>Soluble reactive phosphorus(SRP).The correlation coefficients of organic matter with total phosphorus,BD-P and NaOH-P in sediments of Jinpen reservoir were 0.884,0.831 and0.741,respectively.The linear relationship between organic phosphorus and organic matter was as follows:Organic phosphorus(%)=0.044*organic matter(%)+3.686(R~2=0.810).(2)In Jinpen reservoir,the water was stratified and the dissolved oxygen concentration was quite low at the bottom in summer.This caused the phosphorus released from the sediments into the water and the TP content reduced in the sediments.In the autumn and winter,the water was completely mixed.The operation of water lifting aerator increased the dissolved oxygen at the bottom and raised the water temperature,so the phosphorus in the water migrated to the sediment,resulting in the increase of BD-srP and NaOH-srP in autumn and the organic phosphorus in winter.(3)The soluble phosphorus in the overlying water was 0.03~0.06 mg/L,while the soluble phosphorus concentration in the interstitial water was 0.23~1.84 mg/L.The flux of phosphates released from sediments to the water was 1.841×10~-66 mg/(m~2·d)in Jinpen reservoir.Under reduction conditions,sediment was an important source of dissolved phosphorus at the bottom.(4)The organic matter content of the sedimentation particles was about twice that of the surface sediments.The total phosphorus content in the particles was 599~728 mg/kg,which was slightly lower than the total phosphorus content in the surface sediments(669~775 mg/kg).The NaOH-P in the sedimentation particles was the main component,accounting for about 46.24%of the total phosphorus.From March to May 2017,phosphorus in sedimentation particles was converted by the action of microorganisms and environment influence,and did not accumulate in surface sediments.(5)The water lifting aerator reduced the total phosphorus water concentration by68.29%in the overlying,and the AOC content by 4.378 to 9.021 mg/g in the surface sediments.The total phosphorus in surface sediments increased slightly.In addition,the inorganic phosphorus content increased by 19~27%,but the total organic phosphorus was reduced by 20.2%in the surface sediments.This indicated that the water lifting aerator allowed the sediment to adsorb phosphorus form the water and controlled the release of phosphorus from sediment effectively.