| 摘要: |
| 富营养化湖泊水体中颗粒物的不断富集和沉降加剧了沉积物内源负荷。本文以太湖典型草、藻型湖区为研究对象，开展了为期一年的野外月度调研，分析了两种湖区水样、颗粒物和沉积物中各形态氮含量、赋存形式及其沉积物-水界面交换特征，研究了颗粒物沉降对草/藻型湖区沉积物-水界面氮赋存形态转变及迁移的影响。结果表明，草/藻型湖区水体总氮（TN）浓度年变化范围分别为0.50~1.51 mg/L（均值0.97±0.23 mg/L）和1.77~6.12 mg/L（均值3.67±1.36 mg/L），藻型湖区水体各形态氮浓度普遍高于草型湖区（p < 0.01），且季节性变化更加显著。草/藻型湖区悬浮颗粒物中TN含量年均值分别为6998.48±1413.87 mg/kg和5162.63±2205.13 mg/kg，沉积物TN平均含量分别为4219.75±216.62 mg/kg和3187.88±103.07 mg/kg，呈现草型湖区显著高于藻型湖区（p < 0.05），颗粒物显著高于沉积物（p < 0.05）的特征。NH4+-N是两个湖区颗粒物和沉积物中有效态氮的主要赋存形式，藻型湖区沉积物中NH4+-N的释放主要集中在夏季，而草型湖区则以夏秋两季为主。有效态氮高度富集的颗粒物不断沉降是造成沉积物中氮含量改变的重要原因，且藻型湖区有效态氮所占比例（5.17 %）在藻类水华季节高于草型湖区（4.34 %）。草型系统向藻型系统的转变可能会升高水体颗粒物浓度并加剧沉积物颗粒再悬浮过程，颗粒物沉降和再悬浮交替加剧了沉积物-水界面处氮的交换过程，在未来的湖泊内源氮管理中应更加重视颗粒物的作用。 |
| 关键词: 太湖 草型湖区 藻型湖区 悬浮颗粒物 内源氮负荷 |
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| 基金项目:国家重点研发计划项目(2021YFD1700600，2022YFC3202703，2022YFC3202705)、国家自然科学基金项目(42077310)和江苏省自然科学基金项目(BK20221559)联合资助 |
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| Characteristics and mechanisms of nitrogen exchanges across the sediment-water interface of the macrophyte- and algae-dominated areas under the influence of suspended particulate matter deposition |
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Han Wenxuan, Chen Qiuyu, He Xu, Tan Lixian, Liu Cheng, Zhang Lei
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State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences
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| Abstract: |
| The continuous enrichment and deposition of suspended particulate matter (SPM) aggravate the internal loadings from the sediment of eutrophic lakes. In this study, a monthly field investigation for one year was conducted in the macrophyte- (MDA) and algae-dominated (ADA) areas of Lake Taihu. The nitrogen (N) contents, fractions and sediment exchange characteristics of the sediment-water interface (SWI) in water samples, SPM and sediments were analyzed. The fraction transformation and transport of N across the SWI affected by the SPM deposition in both areas were investigated. The results showed that the annual variation ranges of total nitrogen (TN) in the water of the MDA and ADA were 0.50-1.51 mg/L (average (0.97±0.23) mg/L) and 1.77-6.12 mg/L (average (3.67±1.36) mg/L), respectively. The ADA showed higher concentrations and seasonal variations of various N fractions than those of the MDA. The annual average TN concentrations in the SPM of the MDA and ADA were (6998.48±1413.87) and (5162.63±2205.13) mg/kg, and in the sediment of the MDA and ADA were (4219.75±216.62) and (3187.88±103.07) mg/kg, respectively. The MDA showed significantly higher TN concentrations in both the SPM and the sediment than those of the ADA, with significantly higher TN in the SPM than in the sediment of both areas. NH3-N was the dominant fraction of available N in the SPM and sediment of both areas. The release of NH3-N from the sediment in the ADA mainly occurred in summer, while that in the MDA mainly occurred from summer to autumn. The continuous deposition of the SPM with high concentrations of available N was believed to be an important reason for the transformation of N concentrations and fractions in the sediment. The proportion of available N in the ADA (5.17%) was significantly higher than that in the MDA (4.34%) during algal bloom seasons. The shift from a macrophyte-dominated system to an algae-dominated system might increase the concentration of SPM in the water, thereby intensify the resuspension of sediment particles. Consequently, the alternated deposition and resuspension processes of SPM would exacerbate the N exchanges across the SWI. Therefore, more attention should be paid to the role of SPM during future management of internal N loadings in lakes. |
| Key words: Lake Taihu macrophyte-dominated area algae-dominated area suspended particulate matter internal nitrogen loading |
