Spatial and temporal distribution characteristics of nitrogen and phosphorus and analysis of differences with environmental impact factors in Lake Daihai frozen period and no-frozen period
To investigate the nutrient distribution characteristics in Lake Daihai at different periods and the differential response mechanisms to environmental factors,this study used kriging interpolation,correlation analysis,and analysis of significant differences to analyze the spatiotemporal distribution characteristics of nitrogen and phosphorus in Lake Daihai ecosystem and to investigate their response mechanisms to environmental factors in the frozen(January 2021)and non-frozen(May,July,October)periods of the study.The results showed that the trend of total nitrogen(TN)in Lake Daihai was in the order of spring＞autumn＞summer＞winter and the trend of total phosphorus(TP)was in the order of summer＞autumn＞spring＞winter.From winter to the following autumn,the average concentrations of ammonium nitrogen(NH+4-N)and nitrate nitrogen(NO-3-N)in water decreased and then increased across seasons,whereas TN,dissolved total phosphorus(DTP),and particulate phosphorus(PP)increased and then decreased,with the highest concentrations in summer,primarily in dissolved phosphorus.In winter,TN concentration exhibited a gradient distribution of high in the lake's center and low in the surrounding areas,while TP concentration was uniformly distributed.Apart from NO-3-N being most concentrated in the bottom ice layer,TN,TP,and NH+4-N in the ice sample showed the order of surface ice＞bottom ice＞middle ice.Under the freezing exclusion of salts in the lake,the average separation coefficients of different forms of nitrogen and phosphorus were in the order of NH+4-N＞TP＞TN＞NO-3-N.DTP showed a significant positive correlation with water temperature throughout the year,decreasing in temperature after entering winter along with reduced external phosphorus supply.During the freezing process,TN was more concentrated than TP,resulting in an increased nitrogen-to-phosphorus ratio in the water beneath the ice.Nutrients response to salinity and chlorophyll-a varied over time,influenced by multiple processes such as ice cover isolation,freezing and salt expulsion,internal and external pollution,and microbial metabolism.
Lake Daihainutrientfrozen periodnon-frozen periodwater environmental factorfreezing exclusion of salts
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