Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation
Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation
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DOI：
10.1038/ngeo2543
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发表时间：
2015-11-01
影响因子：
18.3
通讯作者：
Dittmar, Thorsten
中科院分区：
文献类型：
--
作者：
Hawkes, Jeffrey A.;Rossel, Pamela E.;Dittmar, Thorsten
海洋溶解有机碳(DOC)是一个重要的碳库，在大小上与大气二氧化碳相似，但其最古老的形式的命运尚不清楚(1，2)。热水热循环可以促进非活性溶解有机物的降解，在长期的全球碳循环中发挥重要作用。最古老、最顽固的DOC形式，构成了海洋DOC的大部分，可以通过固相萃取来回收。在这里，我们提供了从2009年至2013年在大西洋、太平洋和南大洋的七个喷口地点收集的样品中固相可提取DOC的测量结果，以及镁浓度，这是通过热液系统进行水循环的保守示踪剂。我们发现镁和固相可提取DOC的浓度是相关的，这表明固相可提取DOC在流体温度为212-401摄氏度的热液通风口循环过程中，通过矿化或沉积几乎完全从溶液中损失。在实验室实验中，我们将样品加热到380摄氏度，持续四天，我们发现了类似的去除效率。我们的结论是，光是热降解就可以解释自然水热系统中固相可提取DOC的损失，并且其最大寿命受到水热循环的时间尺度的限制，约为4000万年(3)。
Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood(1,2). Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212-401 degrees C. In laboratory experiments, where we heated samples to 380 degrees C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years(3).