Phosphorus Uptake Potential And Its Response To Exogenous Carbon Of Sediments From Shiwuli River,Chaohu Lake Basin

Shiwuli River runs through the southwestern urban area and suburbs of Hefei City.It is a place for the collection,transmission and purification of domestic sewage and agricultural sewage.The nutrient load of nitrogen and phosphorus in the river is large,and the sediment nitrogen and phosphorus may pass through water-deposition.The interface exchange function enters the overlying water,which makes the pollution of the river more serious and affects the water quality of the western half of Chaohu Lake.Therefore,the river has the characteristics of“source”and“sink”.From July 2017 to May 2018,the surface sediments of 5 points and the corresponding overlying water samples were collected at the frequency of sampling once every two months in the urban-rural gradient direction of the main stream of Shiwuli River.Carry out river water quality assessment and sediment phosphorus morphological analysis;use laboratory culture method to measure the biological and non-bioabsorption potential of sediment phosphorus,and analyze sediment phosphorus uptake for three different exogenous carbons(sodium acetate,glucose,Response level of sodium acetate and glucose mixture;Analyze the equilibrium concentration of phosphorus in sediments,and quantitatively analyze the effect of exogenous carbon?sodium acetate?on the equilibrium concentration of phosphorus,and evaluate the change of phosphorus release risk of sediment caused by exogenous carbon addition.The main research results are as follows:?1?The water body of Shiwuli River is in a weakly oxidizing state and is basically weakly alkaline;the average phosphorus content in the overlying water is 1.05mg·L^-1,and the average SRP content is 0.61 mg·L^-1,and both of them are along the urban and rural areas.The gradient direction increases first,reaches the highest value in SP3,and then gradually decreases;the black odor level of the five sampling points is not up to standard,and both are inferior V black odor levels.?2?The TP mean value of sediments in the Jiulihe River is 1091.61 mg·kg^-1,and the total phosphorus pollution assessment at each point is basically heavy pollution.The average pollution index is as high as 2.599,which is more serious than the pollution of the sediment TN;IP The content accounts for 48%⁹6%of total phosphorus,and Ca-P accounts for the highest proportion of inorganic phosphorus?average value is 42%?;except for TP and IP,Ex-P and pH are significantly positively correlated,most of the rest The correlation between physical and chemical indicators is not significant.?3?There are spatio-temporal differences in SPU_live of Shiwuli River sediment,and the SPU_kill is higher than SPU_biotic.The average contribution rate of biological and abiotic is 15.45%and 84.55%respectively.When no carbon source is added,the bioabsorption potential gradually increases along the urban-rural gradient.The decreasing trend,the mean value is 0.536?g×?g×h?^-1,and the non-bioabsorption potential is smaller in SP1^SP4,but significantly higher than SP5,the average value is3.380?g×?g×h?^-1;5 Sampling points were generally highest in July and September 2017,while non-bioabsorption potential reached its highest value in November 2017,indicating differences in biotic and abiotic effects;In the presence of adding carbons,not only the value of SPU_biotic but the contribution rate of biotic phosphorus uptake had distinctly increased as well.In general,the magnitude and rate of biotic uptake of phosphorus by sediments was highest when sodium acetate was added,followed by glucose,while the effect of mixed carbon was worst,increasing by 19%,12%,and 6%,respectively.?4?Under no carbon added?Scheme 1?,the EPC₀ value of ShiwuliRiver sediments ranges from 0.008 to 0.570 mg·L^-1,with an average of 0.356mg·L^-1.Exogenous carbon addition not only reduced the EPC₀ values of sediments?about 29%?but changed the order of EPC₀ values among the five sampling sites as well.In general,ratio of overlying water SRP concentration to EPC₀ value was 66.7%,and phosphorus adsorption desorption equilibrium saturation EPC_sat<-20%accounted for about 60.0%,indicating that the surface sediments in Shiwuli River were dominated by phosphorus adsorption,namelykeeping phosphorus“sink”state.The input of exogenous carbon increased the proportion of EPC_sat<-20%by 13.3%,which lowered the risk ofphosphorus release from sediments.