海底反风化作用与关键元素循环

Submarine reverse weathering and its effect on oceanic elements cycling

  • 摘要: 海洋环境中的反风化作用是指硅与可溶性阳离子结合形成自生铝硅酸盐矿物(黏土),同时消耗海洋碱度并释放CO2的过程。反风化假说提出半个多世纪以来,作为全球海洋碳、硅和关键元素循环以及海洋碱度的重要调控机制,越来越受到学术界的关注。反风化作用可发生在河口三角洲与边缘海、热液或深埋藏的成岩环境以及深海远洋等环境,但不同海洋环境中的反风化反应从发生时间尺度到反应限制因素都具有差异。反风化作用研究的主要方法包括自生硅酸盐矿物的直接观测、孔隙水与沉积物的化学分析、实验模拟和模型研究等,而反风化作用的程度量化、限制因子解析和对海洋关键元素循环的影响一直是反风化研究的关键问题。当前快速发展的非传统稳定(金属)同位素技术为反风化研究带来了新机遇。东亚大陆边缘发育世界特大河口三角洲、宽广陆架以及特色热液活动区,泥质沉积体系发育,界面交换活跃,是开展大陆边缘反风化研究的天然实验室。

     

    Abstract: Reverse weathering in the marine environment refers to the process in which silicon reacts with soluble cations to form authigenic aluminosilicate minerals (clays), while consuming ocean alkalinity and releasing CO2. The reverse weathering hypothesis was proposed in 1966 and has attracted rapidly increasing research attention over the last two decades. It has been regarded as an important mechanism regulating global carbon, oceanic silicon and key element cycles, and ocean alkalinity. Reverse weathering can occur in various marine environments including estuarine deltas and marginal seas, hydrothermal or deeply buried diagenetic environments, and deep oceans. The reaction timescales of reverse weathering vary widely, ranging from days to millions of years, and the controlling factors of the reactions are also significantly different in different marine environments. The major research methods of reverse weathering include direct observation of authigenic silicate minerals, chemical analysis of pore water and sediments, and experimental simulation and modelling, etc. The quantification of the degree of reverse weathering, the determination of limiting factors, and evaluation of its influence on the key element cycling have always been the key issues in the research of reverse weathering. The rapid development of non-traditional stable (metal) isotopes may allow us to better constrain the reverse weathering research. The East Asian continental margin is featured by the world's largest river delta, wide continental shelf, and characteristic hydrothermal activity, whose unique muddy sedimentary systems and active interface reactions and processes make the continental margin a natural laboratory for the integrated study of reverse weathering.

     

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