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相关概念视频

Radioactive Decay and Radiometric Dating02:48

Radioactive Decay and Radiometric Dating

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Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
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Global Climate Change01:50

Global Climate Change

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Throughout its ~4.5 billion year history, the Earth has experienced periods of warming and cooling. However, the current drastic increase in global temperatures is well outside of the Earth’s cyclic norms, and evidence for human-caused global climate change is compelling. Paleoclimatology, the study of ancient climate conditions, provides ample evidence for human-caused global climate change by comparing recent conditions with those in the past.
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The Carbon Cycle01:14

The Carbon Cycle

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Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
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Carbon-13 (¹³C) NMR: Overview01:10

Carbon-13 (¹³C) NMR: Overview

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Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
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¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

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The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
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Carbon-dioxide Fixation01:28

Carbon-dioxide Fixation

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Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...
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Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
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Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

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为国际放射性碳十年辩护

Timothy I Eglinton1, Heather D Graven2, Peter A Raymond3

  • 1Department of Earth Sciences, ETH Zurich, Zurich, Switzerland.

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
|October 9, 2023
PubMed
概括

放射性碳 (14C) 的水平正在下降,原因是化石燃料和核试验. 未来的测量对了解碳循环至关重要,需要国际合作才能实现更好的碳循环.

关键词:
人类世 (Anthropocene) 是一个人类世.炸弹14C就是一个炸弹.碳循环中的碳循环.气候变化 气候变化 气候变化化石燃料是一种化石燃料.放射性碳 (14C) 是一种

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Characterization, Quantification and Compound-specific Isotopic Analysis of Pyrogenic Carbon Using Benzene Polycarboxylic Acids BPCA
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Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis
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科学领域:

  • 地球和环境科学 地球和环境科学
  • 同位素地球化学 同位素地球化学
  • 大气化学 大气化学

背景情况:

  • 放射性碳 (C) 对于跟踪全球碳循环至关重要.
  • 人类活动,化石燃料燃烧和核武器试验已经显著改变了大气14°C水平.
  • 大气CO2中的C/C12比率目前低于工业化前的水平.

研究的目的:

  • 为了突出化石燃料稀释和C炸弹对全球碳循环的双重影响.
  • 强调需要协调的国际"放射性碳十年",以利用不断增长的测量能力.
  • 概述未来放射性碳研究的关键目标,包括填补观测差距和加强观测网络.

主要方法:

  • 对大气,陆地和海洋水库中历史和当前放射性碳 (C) 数据的分析.
  • 使用14C炸弹作为空海气交换,碳循环和运输过程的追踪器.
  • 审查和提出未来放射性碳研究的战略,包括数据合成和建模.

主要成果:

  • 化石燃料的燃烧逐渐稀释了大气中的C.
  • 核武器试验引入了"炸弹"14C,作为碳循环过程的全球追踪器.
  • 未来14摄氏度下降的速度取决于化石燃料消耗和炸弹14摄氏度交换.

结论:

  • 协调的国际努力至关重要,以最大限度地提高未来放射性碳测量的实用性.
  • 拟定一个"放射性碳十年",以加强观测网络,开发数据工具,并为碳汇建立指标.
  • 了解和预测未来的碳循环动态取决于持续和扩展的放射性碳监测.