喀斯特高原湖泊水体氮形态的时空动态及影响因素OA

Caohai Lake is a typical karst plateau lake on the Yunnan-Guizhou Plateau and plays a crucial role in maintaining regional biodiversity.In this study,we explored the temporal and spatial dynamics of different forms of nitrogen in Caohai Lake,aiming to provide scientific evidence for protecting the aquatic ecology of Caohai Lake and for controlling and managing nitrogen pollution.Based on water quality monitoring data from 2021 to 2023 and historical data from 1983,2005 and 2016,the spatial and tem-poral distribution and influencing factors of nitrogen inputs to Caohai Lake were analyzed.The concen-trations of total nitrogen(TN),ammonia nitrogen(NH4+-N),and nitrate nitrogen(NO3-N)varied signifi-cantly by both year and season(P＜0.05),with dissolved nitrogen(TDN)being dominant.From 1983 to 2023,the concentrations of TN,NH4+-N and NO3-N in Caohai Lake had all increased significantly.Analysis of seasonal variation indicates that nitrogen concentrations in Caohai Lake were higher in win-ter/spring than in summer/autumn,that mineralization and decomposition of organic matter in lake sedi-ments could be the primary driver of seasonal variations in NH4+-N and TN,and that NH4+-N was the pre-dominant form of nitrogen in Caohai Lake and the primary contributor to variation of nitrogen concentra-tion.Differences in the spatial distribution of various nitrogen forms were not significant(P＞0.05).Correlation and redundancy analysis revealed that redox potential(ORP),electrical conductivity(EC),water temperature(WT),pH,and dissolved oxygen(DO)were the primary environmental factors affect-ing the fluctuation of nitrogen concentration in Caohai Lake.To improve the water quality of Caohai Lake,it is necessary to control exogenous pollution and restore a stable grass-type macrophyte dominated clear water lake to enhance self-purification of the lake water.