Mineral protection regulates long-term global preservation of natural organic carbon
Mineral protection regulates long-term global preservation of natural organic carbon
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DOI：
10.1038/s41586-019-1280-6
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发表时间：
2019-06-13
期刊：
影响因子：
64.8
通讯作者：
Galy, Valier V.
中科院分区：
文献类型：
--
作者：
Hemingway, Jordon D.;Rothman, Daniel H.;Galy, Valier V.
光合有机碳生产和呼吸之间的平衡控制着大气成分和气候(1,2)。大部分有机碳在生物圈中被呼吸回到二氧化碳，但一小部分逃脱了再矿化并在地质时间尺度上得以保存(3)。通过去除地球表面减少的碳，这种封存过程促进了大气中氧气的积累(2) 和二氧化碳的去除1。人们提出了两种主要机制来解释有机碳的保存：生化惰性化合物的选择性保存(4,5)和与矿物基质相互作用产生的保护(6,7)。尽管这两种机制可以在一系列环境和时间尺度上运行，但它们在 1,000 年到 100,000 年时间尺度上的全球相对重要性仍然不确定(4)。在这里，我们提供了土壤、沉积物和溶解有机碳中有机碳活化能和相应放射性碳年龄分布的全球数据集。我们发现，在所有含矿物质的样品中，活化能分布随着时间的推移而变宽。这一结果需要增加键强度的多样性，这与有机矿物键的形成一致(8)，但与选择性保存不一致。放射性碳年龄进一步揭示，相对于低能、未结合的有机碳，高能、矿物结合的有机碳可以存在数千年。我们的研究结果为所提议的(7)矿物保护在促进有机碳保存方面的重要性提供了全球一致的证据。我们建议，对古代沉积物中键强度多样性的类似研究可能会揭示有机碳保存（以及大气成分和气候）如何以及为何随着地质时期的变化而变化。
The balance between photosynthetic organic carbon production and respiration controls atmospheric composition and climate(1,2). The majority of organic carbon is respired back to carbon dioxide in the biosphere, but a small fraction escapes remineralization and is preserved over geological timescales(3). By removing reduced carbon from Earth's surface, this sequestration process promotes atmospheric oxygen accumulation(2) and carbon dioxide removal1. Two major mechanisms have been proposed to explain organic carbon preservation: selective preservation of biochemically unreactive compounds(4,5) and protection resulting from interactions with a mineral matrix(6,7). Although both mechanisms can operate across a range of environments and timescales, their global relative importance on 1,000-year to 100,000-year timescales remains uncertain(4). Here we present a global dataset of the distributions of organic carbon activation energy and corresponding radiocarbon ages in soils, sediments and dissolved organic carbon. We find that activation energy distributions broaden over time in all mineral-containing samples. This result requires increasing bond-strength diversity, consistent with the formation of organo-mineral bonds(8) but inconsistent with selective preservation. Radiocarbon ages further reveal that high-energy, mineral-bound organic carbon persists for millennia relative to low-energy, unbound organic carbon. Our results provide globally coherent evidence for the proposed(7) importance of mineral protection in promoting organic carbon preservation. We suggest that similar studies of bond-strength diversity in ancient sediments may reveal how and why organic carbon preservation-and thus atmospheric composition and climate-has varied over geological time.