地学前缘 ›› 2022, Vol. 29 ›› Issue (5): 35-46.DOI: 10.13745/j.esf.sf.2021.9.12

• 海洋化学 • 上一篇    下一篇

春季黄、渤海沉积物中CH4和N2O的垂向分布特征研究

李思琦1,2,3(), 陈烨1,2,3, 尹霞2,3,4, 臧昆鹏5, 甄毓2,3,4,*()   

  1. 1.中国海洋大学 海洋生命学院, 山东 青岛 266003
    2.青岛海洋科学与技术国家实验室 海洋生态与环境科学功能实验室, 山东 青岛 266237
    3.海洋环境与生态教育部重点实验室, 山东 青岛 266100
    4.中国海洋大学 环境科学与工程学院, 山东 青岛 266100
    5.国家海洋环境监测中心, 辽宁 大连 116023
  • 收稿日期:2020-07-10 修回日期:2020-11-12 出版日期:2022-09-25 发布日期:2022-08-24
  • 通讯作者: 甄毓
  • 作者简介:李思琦(1993—),女,博士研究生,海洋生物学专业。E-mail: lisiqi.sy@outlook.com
  • 基金资助:
    国家重点研发计划项目(2017YFC1404404);国家自然科学基金项目(41620104001);国家自然科学基金项目(41806131);青岛海洋科学与技术国家实验室鳌山科技创新计划项目(2016ASKJ02);中央高校基本科研业务费专项(202061013)

Vertical distributions of CH4 and N2O in sediments of the Bohai and Yellow Seas in spring

LI Siqi1,2,3(), CHEN Ye1,2,3, YIN Xia2,3,4, ZANG Kunpeng5, ZHEN Yu2,3,4,*()   

  1. 1. College of Marine Life Science, Ocean University of China, Qingdao 266003, China
    2. Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
    3. Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao 266100, China
    4. College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
    5. National Marine Environmental Monitoring Center, Dalian 116023, China
  • Received:2020-07-10 Revised:2020-11-12 Online:2022-09-25 Published:2022-08-24
  • Contact: ZHEN Yu

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摘要：

本研究分别利用顶空平衡法与qPCR技术测定了2018年春季黄、渤海5个典型站位柱状沉积物中甲烷(CH4)和氧化亚氮(N2O)浓度及产甲烷菌与硫酸盐还原菌功能基因拷贝数,并分析了其与间隙水中相关环境因子的关系。沉积物上方水文条件的差异以及其中复杂的碳氮生物地球化学过程使得CH4和N2O浓度呈现出明显的空间和垂直变化。结果显示,沉积物中CH4浓度为0.23~0.92 μmol·kg-1,N2O浓度为18.90~104.96 nmol·kg-1。总体来说,渤海沉积物中CH4和N2O平均浓度高于黄海。垂向分布上,CH4浓度均随深度增加逐渐升高, $\text{SO}_{4}^{2-}$浓度随深度增加逐渐降低,并与CH4浓度呈镜像关系,产甲烷菌与硫酸盐还原菌的丰度也遵循着同样规律,这表明沉积物中产甲烷作用受$\text{SO}_{4}^{2-}$浓度的抑制。 mcrA基因拷贝数平均值为渤海低于黄海。除3500-7站外,沉积物中mcrA基因拷贝数随深度增加而升高。各站位mcrA 基因丰度与CH4浓度均无显著相关性,且mcrA丰度与$\text{SO}_{4}^{2-}$浓度之间也未检测到显著相关性。dsrB基因拷贝数远高于mcrA基因拷贝数,且两者相差至少两个数量级。 dsrB基因拷贝数随深度逐渐增加,直至10 cm左右,随后至沉积物底部逐渐减少。各站位dsrB基因拷贝数与CH4浓度剖面略有镜像关系,但均未检测到显著负相关性。以上结果均表明沉积物中存在着同时消耗沉积物中$\text{SO}_{4}^{2-}$与CH4的其他作用。N2O浓度随深度增加先降低,在深度30 cm以下逐渐升高。间隙水中$\text{NO}_{3}^{-}$和$\text{NO}_{2}^{-}$浓度均随深度减小,同时$\text{NH}_{4}^{+}$浓度与其呈相反趋势。沉积物中N2O与$\text{NO}_{2}^{-}$及$\text{NO}_{3}^{-}$浓度均呈正相关,且前者相关性较高,说明反硝化作用是沉积物中N2O产生的主要过程。这些结果为进一步了解近岸陆架海域沉积物中CH4和N2O的来源、分布及碳氮生物地球化学循环提供了参考资料。

关键词: 甲烷, 氧化亚氮, 渤海, 黄海

Abstract:

In this study, the head-space equilibrium and quantitative PCR methods were used respectively to obtain the concentrations of methane (CH4) and nitrous oxide (N2O) and the vertical abundances of methanogens and SRB in five representative sediment cores in the Bohai and Yellow Seas during two cruises in spring 2018. The relationships between these measurements and the related environmental parameters in pore water were also analyzed. The CH4 and N2O concentrations showed obvious spatial and vertical variations, due to the differences in the hydrological conditions above the sediment and the complexity of carbon/nitrogen biogeochemical processes in sediment cores. The average CH4 and N2O concentrations in sediments ranged between 0.23-0.92 nmol·kg-1 and between 18.90-104.96 nmol·kg-1, respectively, and they were higher overall in the Yellow Sea than in the Bohai Sea. The CH4 concentrations in sediments increased with increasing depth, whereas the $\text{SO}_{4}^{2-}$ concentrations decreased steadily with depth as in a mirror-image relationship with CH4 concentrations, while the abundances of methanogens and sulfate-reducing bacteria followed the same trend, indicating the CH4 production rate in sediments was controlled by the $\text{SO}_{4}^{2-}$ concentration in pore water. The average copy number of the mcrA gene was lower in the Bohai Sea than in the Yellow Sea and increased with depth at all stations except station 3500-7; whilst no significant correlation was detected at all stations between the mcrA gene abundance and CH4 concentration, and the same held true for $\text{SO}_{4}^{2-}$. The copy number of the dsrB gene was at least 2 orders of magnitude higher than that of the mcrA gene and, at all stations, increased at depths above 10 cm then gradually decreased till the bottom of sediments; and there was a weak mirror-image relationship between the dsrB gene copy number and CH4 profiles at all stations, although no significant negative correlation was found between the two. The above results indicate there are other processes that consume CH4 and $\text{SO}_{4}^{2-}$ in sediments. The N2O concentrations roughly decreased with increasing depth but gradually increased at depths below 30 cm; whilst the $\text{NO}_{3}^{-}$ and $\text{NO}_{2}^{-}$ concentrations gradually decreased with depth at all stations while the $\text{NH}_{4}^{+}$ profiles followed the opposite trend. The significant positive correlation between the N2O and $\text{NO}_{2}^{-}$ concentrations and slightly weaker positive correlation between N2O and $\text{NO}_{3}^{-}$ in sediments indicate that denitrification is the main process for the N2O production in marine sediments. These results provide a reference for further understanding the source and distribution of CH4 and N2O, as well as the carbon and nitrogen cycles in the sediments of the continental shelf.

Key words: methane, nitrous oxide, Bohai Sea, Yellow Sea

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