Study On The Influence Of River-Lake Relation Change On The Bioavailability Of Organic Phosphorus In Tongjiang Lakes Sediments

The improved Hedley continuous extraction method,enzymatic hydrolysis technique,liquid phase ³¹P-NMR method,UV-visible spectroscopy?UV-Vis?and infrared spectroscopy?FT-IR?were used to characterize the large-scale Tongjiang Lake in the dry season of 2007 and 2012.Changes in OP composition,structure,morphology and bioavailability of surface sediments from 38 different elevations.In order to reveal the changes in the relationship between the Tongjiang Lake and the Yangtze River since the operation of the Three Gorges Water Conservancy Project,the water level of the Tongjiang Lake has decreased during the dry season,the low water level is prolonged,the sediment exposure time is advanced and prolonged,and the OP activity of the sediment is further The impact of the change of rivers and lakes on the potential release risk of sediment OP is discussed,in order to provide a theoretical basis for protecting the water quality and ecological environment of Tongjiang Lake.The main conclusions of the paper are as follows:?1?The liquid phase 31P-NMR study found that the phosphorus composition of the sediments in the Tongjiang Lake was Ortho-P>Monoester-P>DNA>Pyro-P>phosphonate.The content of Phosphonate is mainly characterized by Monoester-P and DNA.With the change of rivers and lakes,the content of Biogenic-P in the sediments of Tongjiang Lake in 2012 is increasing compared with that in 2007.Difference?ANOVA,P<0.05?,the distribution of Biogenic-P was higher in the elevation range,and the higher the content of Biogenic-P in each elevation in 2012 was greater than that in 2007;the sediments of Tongjiang Lake in 2012 were The composition of OP increased compared with that of 2007.The content of Monoester-P,DNA and Phosphonate in the sediments of Poyang Lake in 2012 increased by 42%,25%and 7%respectively compared with 2007.The OP components of Dongting Lake increased by 127.%,36%and 2%.It indicates that the exposure time of sediments in Tongjiang Lake caused by the change of rivers and lakes will affect the change of OP content in sediments,and the two lakes OP group due to the increase of sediment OM,metal content and the environment of two lakes.There are differences in the growth of points.?2?Through improved Hedley continuous extraction and enzymatic hydrolysis studies,it was found that the OP content of sediments in Poyang Lake of Tongjiang Lake was:NaOH-OP>NaHCO₃-OP>H₂O-OP>HCl-OP,Dongting Lake sediments The order of morphological organic phosphorus content was:NaOH-OP>HCl-OP>NaHCO₃-OP>H₂O-OP.The OP of the sediments of Tongjiang Lake showed a higher elevation in the elevation distribution,and the higher the content,along with the rivers and lakes.The relationship between the OP content of all forms in 2012 was greater than that in2007.The OP content of OP in the extracted OP was:NaOH-OP>NaHCO₃-OP>H₂O-OP,different forms of OP extract The content of orthophosphate released in the order was APase+PDEase+Phytase>APase+PDEase>Apase,and the total content of hydrolyzable phosphorus in each extracted state showed a trend of change from 2012 to 2007,in which H₂O-OP was active.Ester phosphorus is the main component,NaHCO₃-OP and NaOH-OP are mainly phytate phosphorus,diester phosphorus is mainly distributed in H₂O-OP and NaOH-OP,and the active monoester in H₂O-OP changes with the relationship between rivers and lakes.Phosphorus content increased,diester phosphorus and phytate phosphorus content did not change significantly,bioavailability Strong;the content of active monoester phosphorus and phytate phosphorus in NaHCO₃-OP increased,the change of diester phosphorus was smaller,the bioavailable phosphorus increased;the content of active monoester phosphorus in NaOH-OP increased.The content of phytate phosphorus is decreasing and the bioavailability is enhanced.?3?With the change of rivers and lakes,A253/A203 and A260 in the extracted OP showed an increasing trend,and E3/E4 and E2/E3 showed a downward trend,indicating that the sediment DOM structure became complicated,the molecular weight became larger,and the aromatic hydrocarbon substituents increased.And the degree of humification increased and the sediment OM became relatively stable,resulting in increased sediment OM content,which led to an increase in sediment OP;active monoester phosphorus,diester phosphorus and phytate-like phosphorus as H₂O-OP,NaHCO₃-OP The active OP components that can be bio-utilized in OP and NaOH-OP vary with the relationship between rivers and lakes,and their contents have increased to varying degrees.This is mainly due to the change of the relationship between rivers and lakes,which leads to the surface OM,metal content,microbial quantity,The number of phytoplankton was related to the degree of bacterial metabolism.In 2012,the OP content of surface sediments in Poyang Lake increased by 35.6t compared with that in 2007,and the potential release of OP was 27.5t,accounting for 77.24%of the increase of OP in each form;The OP content of Dongting Lake increased by 161.1t,and the potential release of OP was 67.2t,accounting for 41.7%,indicating that the change of rivers and lakes led to an increase in the potential release potential of sediment OP,which aggravated the deterioration of lake water quality and Eutrophication risks.