Ocean process tracers: nitrogen isotopes in the ocean
Ocean process tracers: nitrogen isotopes in the ocean
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发表时间：
2009
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通讯作者：
D. Sigman;K. Karsh;K. Casciotti
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作者：
D. Sigman;K. Karsh;K. Casciotti
介绍氮有两种稳定的同位素，N和N(原子质量分别为14和15)。氮是两者中含量较丰富的一种，占自然界中发现的氮的99.63%。物理、化学和生物过程区分这两种同位素，导致在海洋环境中发现的不同形态的氮之间的氮与氮的比率存在细微但可测量的差异。氮是海洋生物量的核心组成部分，也是所有浮游植物所需的主要营养物质之一。从这个意义上说，生物可利用氮(或固定氮，即非氮氮)代表了海洋中生物地球化学循环的基本模式。然而，N与其他营养物质的不同之处在于，它的海洋来源和汇主要是内部和生物的，海洋固定氮提供了海洋中固定N的大部分，海洋反硝化作用去除了它。氮同位素提供了一种研究海洋固定氮的输入/输出预算及其在海洋中的循环的方法。在这篇综述中，我们概述了N循环过程的同位素系统学及其对海洋中主要N储量的同位素组成的影响。这一信息为审议海洋科学中可应用氮同位素的广泛问题提供了一个起点。
Introduction Nitrogen has two stable isotopes, N and N (atomic masses of 14 and 15, respectively). N is the more abundant of the two, comprising 99.63% of the nitrogen found in nature. Physical, chemical, and biological processes discriminate between the two isotopes, leading to subtle but measurable differences in the ratio of N to N among different forms of nitrogen found in the marine environment. Nitrogen is a central component of marine biomass and one of the major nutrients required by all phytoplankton. In this sense, biologically available (or ‘fixed’, i.e., non-N2) N is representative of the fundamental patterns of biogeochemical cycling in the ocean. However, N differs from other nutrients in that its oceanic sources and sinks are dominantly internal and biological, with marine N2 fixation supplying much of the fixed N in the ocean and marine denitrification removing it. The N isotopes provide a means of studying both the input/output budget of oceanic fixed N and its cycling within the ocean. In this overview, we outline the isotope systematics of N cycle processes and their impacts on the isotopic composition of the major N reservoirs in the ocean. This information provides a starting point for considering the wide range of questions in ocean sciences to which the N isotopes can be applied.