| 西沙群岛东岛潟湖沉积物碳、氮元素地球化学特征及其指示的环境变化 |
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| 引用本文： | 刘晓瞳,葛晨东,邹欣庆,黄梅,唐盟,李亚丽.西沙群岛东岛潟湖沉积物碳、氮元素地球化学特征及其指示的环境变化[J].海洋学报,2017,39(6):43-54. |
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| 作者姓名： | 刘晓瞳 葛晨东 邹欣庆 黄梅 唐盟 李亚丽 |
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| 作者单位： | 南京大学 中国南海研究协同创新中心, 江苏 南京 210023;南京大学 地理与海洋科学学院, 江苏 南京 210023;南京大学 海岸与海岛开发教育部重点实验室, 江苏 南京 210023 |
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| 基金项目： | 国家自然科学基金项目（41530962）；中国南海研究协同创新中心2015年度两项重大任务"基于资源分布特点的我国南海主要岛礁战略地位研究"和"南海疆界线位置地学依据研究"。 |
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| 摘 要： | 根据对西沙群岛东岛潟湖沉积柱样DD-01粒度特征，210Pb年代学，C、N元素地球化学，有机碳同位素（δ13C）以及生物残留组分的分析，探讨了东岛沉积环境的演变。结果显示，沉积柱剖面自下而上可分成4段:（1）34~40 cm的沉积层受鸟粪影响较大，TN、TOC含量分别介于0.15%~0.27%及1.78%~2.8%，δ13C值介于-24.86‰~-23.84‰，可见大量鸟粪沉积，植物颖果以及淡水相介形类残体；（2）28~34 cm （年代约132 a BP）的沉积层中淡水相的介形类以及植物颖果和鸟粪沉积几乎绝迹，海相有孔虫以及海胆刺残体数量激增，TN含量介于0.05%~0.06%，TOC含量在0.4%~1.17%之间，分别降至相对低值；δ13C值变轻，介于-25.95‰~-25.45‰；平均粒径较粗，稳定在1.3Φ左右；TIC含量较高，介于10.95%~11.26%，接近纯净碳酸盐的含量。C、N元素的含量较上下层位均出现了剧烈的变化，这可能受到了海洋沉积动力事件影响，使得东岛的生态环境产生了剧烈的变化；（3）19~28 cm 深度，TN、TOC出现增加的趋势，沉积物中又重现植物颖果及其残体，此段沉积物更多受到牛粪的影响，δ13C值保持在较轻的水平；（4）19 cm（年代约90 a BP）处至表层，TN、TOC含量快速波动增长，受到鸟类种群恢复带来的大量鸟粪输入的影响，δ13C的值也出现了变重的趋势。
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| 关 键 词： | TOC δ13C 环境变化 人类活动 西沙群岛东岛 |
| 收稿时间： | 2016/8/30 0:00:00 |
| 修稿时间： | 2017/1/17 0:00:00 |
Carbon, Nitrogen geochemical characteristics and their implications on environmental change in the lagoon sediments of the Dongdao Island of Xisha Islands in South China Sea |
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| Liu Xiaotong,Ge Chendong,Zou Xinqing,Huang Mei,Tang Meng and Li Yali.Carbon, Nitrogen geochemical characteristics and their implications on environmental change in the lagoon sediments of the Dongdao Island of Xisha Islands in South China Sea[J].Acta Oceanologica Sinica (in Chinese),2017,39(6):43-54. |
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| Authors: | Liu Xiaotong Ge Chendong Zou Xinqing Huang Mei Tang Meng and Li Yali |
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| Institution: | Collaborative Innovation Center of South China Sea Studies, Nanjing University, Nanjing 210023, China;School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210023, China;The Key Laboratory of Coast&Island Development of Education, Nanjing University, Nanjing 210023, China |
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| Abstract: | A sediment core, DD-01, was collected from Cattle Pond, on Dongdao Island in the Xisha Islands. Measurements of grain size, C and N elemental geochemistry, δ13C and biological remains were taken, and a 210Pb chronology established, to study the evolution of the sedimentary environment of Dongdao Island. The results indicate that 4 depositional units can be distinguished between the bottom and the surface layers. The sediment unit below 34 cm was more influenced by guano than the others; its TN and TOC contents are between 0.15%-0.27% and 1.78%-2.8% respectively, δ13C ranges from -24.86‰ to -23.84‰, and there is a large amount of guano sediment, caryopses, and fresh Ostracodes residues. At a depth of 28-34 cm (about 132 a BP), the guano sediment, caryopses and fresh Ostracodes residues disappear, and the number of foraminifers and sea urchin spines increases sharply. The TOC values in this unit are between 1.25% and 2.28%, and TN ranges from 0.11% to 0.29%. δ13C values vary in the range of -25.95‰ to -25.45‰, which is much lower than those in the top 28 cm and those in the bottom 34 cm. A larger mean grain size was also observed, with a stable value of 1.3 Φ, and TIC values were higher at between 10.95% and 11.26%. All of this data shows that this sediment unit may have been influenced by marine dynamic events, which changed the environment of Cattle Pond over a long period. At a depth of 19-28 cm, TN and TOC show increasing trends, and the caryopses reappear. The sediment is more affected by cow-dung and the δ13C remains at a low level. Above 19 cm (about 90 a BP), the TN and TOC values increase rapidly but with fluctuations, suggesting an increasing source of organic matter. An increasing trend in δ13C is related to the input of guano, which was caused by recovery of the sea bird population. |
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