| 引用本文: | 胡婧,谭亮成,李宇亮,韩永明,蓝江湖,刘卫国.2026.四海龙湾表层沉积物氮同位素组成特征及其影响机制[封面文章][J].地球环境学报,17(3):611-621 |
| HU Jing,TAN Liangcheng,LI Yuliang,HAN Yongming,LAN Jianghu,LIU Weiguo.2026.Characteristics and influence mechanisms of nitrogen isotope composition in surface sediments of the Sihailongwan Maar Lake[Cover][J].Journal of Earth Environment,17(3):611-621 |
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| 摘要: |
| 湖泊沉积物氮同位素能够记录人类活动和气候变化信息, 因而在湖泊氮循环和古环境研究中具有重要意义。然而, 由于氮循环过程伴有氮同位素分馏现象, 致使湖泊氮同位素的解读存在一定争议。文章以四海龙湾为研究对象, 通过表层沉积物氮同位素、湖水和孔隙水中的硝酸盐氮、氧同位素, 探讨该湖泊表层沉积物中氮同位素的变化规律及其影响机制。结果显示: 表层沉积物中δ15N变化幅度较小, 处于2.4‰—3.1‰, 孔隙水中硝酸盐氮、氧同位素的变化范围分别为1.4‰—4.9‰和3.3‰—33.9‰, 均未呈现出明显的变化规律。表层沉积物硝酸盐氮、氧同位素的变化范围分别为0.4‰—7.0‰和11.7‰—33.5‰; 随着湖水深度的增加, 表层沉积物中硝酸盐含量升高, 同时硝酸盐氮同位素偏正, 且与湖水深度呈现显著相关性。依据氮转化过程中的同位素分馏机制, 推断厌氧氨氧化是该表层沉积物硝酸盐的主要生成路径, 基于此线性关系, 初步提出四海龙湾湖泊表层沉积物水溶性硝酸盐氮同位素具备成为反演湖水深度变化的地球化学指标的潜力。研究结果为湖泊沉积物氮同位素在古环境研究中的应用提供了基础支撑。 |
| 关键词: 四海龙湾 表层沉积物 氮同位素 厌氧氨氧化 湖水深度 |
| DOI：10.7515/JEE2024123 |
| CSTR：32259.14.JEE2024123 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41991252，41991250）；中国科学院仪器设备功能开发技术创新项目（2024g103） |
| 英文基金项目: |
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| Characteristics and influence mechanisms of nitrogen isotope composition in surface sediments of the Sihailongwan Maar Lake[Cover] |
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HU Jing1，TAN Liangcheng1，LI Yuliang2，HAN Yongming1，LAN Jianghu1，LIU Weiguo1
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1. State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061 , China ； 2. School of Water and Environment, Chang'an University, Xi'an 710054 , China
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| Abstract: |
| Background, aim, and scope The nitrogen isotopes (δ15N) in lake sediments can record information on human activities and climate change, making them of great significance in the study of lake nitrogen cycling and paleoenvironment. However, due to the nitrogen cycle process accompanied by nitrogen isotope (δ15N) fractionation, there is some controversy over the interpretation of nitrogen isotopes (δ15N) in lakes. This study focuses on nitrogen isotopes of different components in surface sediments to clarify the main influencing factors of nitrogen isotopes and their geochemical implications in the Sihailongwan region. Materials and methods This study takes Sihailongwan (42°17′00″—42°17′24″N, 126°35′51″—126°36′24″E) as the object, and explores the changes and influencing mechanisms of nitrogen isotopes (δ15N) in 15 surface sediments (D1—D15) of the lake through surface sediment nitrogen isotopes (δ15N), nitrogen and oxygen isotopes of nitrate (δ15N-NO3- and δ18O-NO3-) in 29 lake water (W-1—W-29). Results The research results show that the variation amplitude of nitrogen isotopes (δ15N) in surface sediments is relatively small, ranging from 2.4‰ to 3.1‰. The variation range of nitrogen and oxygen isotopes of nitrate (δ15N-NO3- and δ18O-NO3-) in pore water is 1.4‰ to 4.9‰ and 3.3‰ to 33.9‰, respectively, and no obvious change pattern is shown. The variation range of nitrogen and oxygen isotopes of nitrate (δ15N-NO3- and δ18O-NO3-) in surface sediments is 0.4‰—7.0‰ and 11.7‰—33.5‰, respectively. Discussion We found that nitrogen isotopes of nitrate (δ15N-NO3-) of water-soluble in the sediment decreased with increasing sediment organic nitrogen isotopes. It indicates that the depletion of organic nitrogen in sediments is accompanied by the process of nitrate production. Firstly, organic nitrogen is mineralized to ammonia nitrogen, and the residual particulate organic nitrogen isotopes in the sediment become progressively more positive as the mineralization process proceeds. Then, both the nitrification and the anaerobic ammonia oxidation process could convert the mineralized ammonia nitrogen to nitrate. We also found that as the depth of the lake water increases, the nitrate content in surface sediments increases, and the nitrate nitrogen isotope is positively correlated with the depth of the lake water. Based on the isotope fractionation mechanism during nitrogen conversion, it is inferred that anaerobic ammonia oxidation is the main pathway for nitrate production in the surface sediment. Conclusions Based on this linear relationship, it is preliminarily proposed that the water-soluble nitrogen and oxygen isotopes of nitrate (δ15N-NO3- and δ18O-NO3-) in the surface sediments of Sihailongwan Lake have the potential to become geochemical indicators for inverting changes in lake water depth. Recommendations and perspectives This study provides fundamental research support for the application of nitrogen isotopes (δ15N) in lake sediment in paleoenvironmental research. |
| Key words: Sihailongwan surface sediment nitrogen isotope anaerobic ammonia oxidation water depth |
