Distribution And Equilibrium Of Phosphorus In Multi-medium System In Ulansuhai

Exogenous input and endogenous circulation of phosphorus load in lakes jointly determine the cyclic balance process of phosphorus nutrients in lakes,and the balance and retention of phosphorus in lakes will affect the migration and transformation process of nutrient components in different media,thus leading to differences in the distribution of phosphorus nutrients among different media.Therefore,it is very important to clarify the phosphorus balance and retention dynamics for the quantitative distribution of phosphorus in different media and the eutrophication control of lake ecosystems.Based on the current environmental pollution situation of Ulansuhai,this study focused on the chain response relationship of phosphorus load entering and leaving the lake during the environmental process of Ulansuhai,combined with the consideration of phosphorus storage in various media,and quantitatively analyzed the distribution of phosphorus in different media in the lake.The main research results are as follows:(1)According to the water quality monitoring data of Ulansuhai from 2011 to 2021,the overall pattern of seasonal variation of TP concentration was winter >spring > autumn > summer.In the process of interannual variation,the TP concentration of the whole water body in Ulansuhai decreased year by year.The TP concentration of the upper lake drained into the lake mouth and the northern area was almost higher than that of the central and southern lakes and the area near the outlet of the drainage canal.In the response relationship between water TP concentration and environmental factors,most of the water environmental factors were significantly correlated with water TP concentration,and showed obvious inter-annual and seasonal differences,which laid the foundation for establishing the response relationship between water TP and annual phosphorus retention.(2)From 2011 to 2021,the TP concentration and load of total drainage into the lake showed a decreasing trend on the whole,which was the main contributor of TP load into the lake of Ulansuhai,and the TP concentration and load out of the lake of Wumao were relatively stable.According to the results of the P balance model,the average annual P retention in the lake area is 177.3t/a,and the retention rate is 68%.Moreover,when the absorption capacity of each medium in the lake reaches the upper limit,the P balance of the lake will be staggered.Through the construction of multiple linear regression model,the results show that the TP concentration of water body can be better explained by salinity,water temperature,p H,and annual phosphorus retention.(3)According to the annual variation characteristics of TP load in and out of Ulansuhai,the variation characteristics of TP content and reserves in water,sediments,upwelling plants and submerged plants from May to August were analyzed.The average content in water was 0.027 mg/L,and TP reserves were 43.02 t.The average TP content in the sediments was 1.587 mg/g(dry weight),and the average reserve was 418.45 t.The average TP content was 1.23 mg/g(dry weight)and the average TP reserve was 454.55 t(dry weight).The average content of TP in submerged plants was 1.61 mg/g and the average reserve of TP was 47.73 t.According to the results of the distribution of phosphorus retention in the lake area,63% of TP retention was in emergent plants,33% of TP retention was in sediments,3% of TP retention was in submerged plants and 0.1% of total TP retention was in algae.