Evaluation of Eutrophication Status and Analysis of Its Variation Characteristics in Yangzonghai Lake during the 13th Five-Year Plan Period

Based on the routine monitoring data of pH,SD,TP,COD_Mn and Chla at 3 sampling sites in Yangzonghai Lake during the 13th Five-Year Plan period （2016—2020）,the eutrophication state of water was evaluated by comprehensive nutrition state index method,the spatial and temporal variation characteristics of eutrophication degree and Pearson correlation analysis were carried out with the help of Origin,ArcGIS and SPSS.The results showed that during the 13th Five-Year period,the overall degree of eutrophication in Yangzonghai Lake was not high,which was graded as poor nutrition.However,the average concentrations of TP and TN at the 3 sites were close to or higher than the water bloom threshold,potential ecological risks still exist;the eutrophication degree of the 3 monitoring points in Yangzonghai Lake showed a trend of increasing first and then decreasing in terms of time change;in the change of space,the degree of eutrophication in the northern area of YangzonghaiLake was relatively high,and the southern area was relatively low.Pearson correlation analysis showed that the eutrophication status of YangzonghaiLake was mainly affected by TN and NH₄⁺-N.