岱海冰封期与非冰封期氮磷分布及影响因素差异分析

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

为揭示岱海不同时期营养盐分布特征及与环境因子的响应机制差异,基于2021年1月(冰封期)和5、7、10月(非冰封期)岱海水样及冰样的实测数据,运用克里金插值、相关性分析、差异显著性分析方法,分析岱海氮、磷时空分布特征,探讨其与环境因子在冰封期与非冰封期的响应机制。结果表明:岱海水体中总氮(TN)变化趋势为春季>秋季>夏季>冬季;总磷(TP)变化趋势+-为夏季>秋季>春季>冬季。从冬季到次年秋季,水体中氨氮(NH_(4)^(+)-N)和硝态氮(NO_(3)^(-)-N)的平均浓度呈先减少后增加的变化趋势,而TN、溶解性总磷(DTP)和颗粒态磷(PP)浓度呈先增加后减少的变化趋势,且夏季浓度最高,以溶解态磷为主。冬季TN浓度呈湖心处高四周低的分布,TP浓度整体分布均匀。除NO_(3)^(-)-N在底层冰中浓度最大外,冰体中TN、TP和NH4-N均表现为表层冰>底层冰>中层冰。在湖体冻结排盐作用下,不同形态氮、磷平均分离系数大小依次为NH4-N>TP>TN>NO_(3)^(-)-N。DTP与水温全年呈显著正相关,入冬后温度降低且外源磷供给减少,而结冰过程中TN浓缩程度高于TP,导致冰下水体的氮磷比增大。不同时期水体中营养盐与盐度、叶绿素a的响应存在明显差异,这一结果受冰盖阻隔、冻结排盐、内外源污染以及微生物代谢等多个过程的共同控制。

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(NH4-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 NH4+-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 NH4+-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.