Flash heating boosts the potential for mechanochemical energy sources for subglacial ecosystems
Flash heating boosts the potential for mechanochemical energy sources for subglacial ecosystems
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DOI：
10.3389/fgeoc.2023.1180893
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发表时间：
2023-05
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影响因子：
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通讯作者：
J. Stone;J. Edgar;J. Rutherford;Beatriz Gill-Olivas;M. Tranter;Jamie A. Gould;C. Xavier;J. Telling
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文献类型：
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作者：
J. Stone;J. Edgar;J. Rutherford;Beatriz Gill-Olivas;M. Tranter;Jamie A. Gould;C. Xavier;J. Telling
冰下环境蕴藏着能够影响生物地球化学循环的微生物生态系统的多样性。然而，冰下环境的黑暗和隔离限制了微生物代谢的能量来源。最近人们认识到，在以湿为基础的地区，这些微生物的能量来源是冰川基岩机械破裂后发生的岩石-水反应。这些机械化学反应在0°C下与矿物表面缺陷（Si•和SiO•）反应产生H2和H2O2，并从矿物结构中释放铁，为微生物代谢提供电子供体和受体。然而，H2O2和H2的产生可能被低估了，因为岩石磨损部位的温度可能大大高于0°C，因为冰川“滑动和磨碎”岩石，可能会加速机械化学反应的速度。尽管如此，快速加热对随后的低温机械化学反应的影响还有待研究。在这里，我们研究了水与一系列地面岩石和矿物在“闪热”到30、60或121°C后的低温（0°C）孵育过程中H2、H2O2和Fe的产生。我们发现，短暂增加（加热5-10分钟）到中等温度（30或60°C）可以显著提高H2的产生速度，而短期加热到121°C会产生更大的氢气爆发。此外，黄铁矿容易破碎，可能会将大量的Fe2+释放到冰下系统中，并由于产生的大表面积（比其他材料大10倍）而促进机械化学反应。我们提供了水与破碎的黄铁矿反应产生H2的第一个证据，并表明破碎的黄铁矿比硅酸盐对冰下H2O2的产生有更大的影响。我们得出结论，在冰下生态系统中可以产生Fe2+和H2爆发形式的电子供体，这可能与从破碎的黄铁矿中产生的大量H2O2有关。这表明岩石-水的机械化学反应可能是冰下环境中比以前认识到的更大的能量来源。
Subglacial environments harbour a diversity of microbial ecosystems capable of influencing biogeochemical cycles. However, the darkness and isolation of subglacial environments limit the energy sources available for microbial metabolism. A recently recognised energy source for these microbes in wet-based regions is the rock-water reactions that occur after the mechanical fracturing of glacial bedrock. These mechanochemical reactions produce H2 and H2O2 at 0°C from reactions with mineral surface defects (Si• and SiO•) and release Fe from within the mineral structures, providing electron donors and acceptors for microbial metabolism. However, the production of H2O2 and H2 may be underestimated as temperatures at rock abrasion sites can increase substantially above 0°C as glaciers “slip and grind” rocks, potentially accelerating the rates of mechanochemical reactions. Despite this, the effect of rapid heating on subsequent low-temperature mechanochemical reactions has yet to be examined. Here, we investigate H2, H2O2, and Fe production during low-temperature (0 °C) incubations of water with a range of ground rocks and minerals following “flash heating” to 30, 60, or 121 °C. We show that transient increases (as little as 5–10 min of heating) to moderate temperatures (30 or 60 °C) can significantly increase the rate of H2 production, while short-term heating to 121 °C generates larger bursts of H2. In addition, pyrite is easily crushed, potentially releasing large quantities of Fe2+ into subglacial systems and promoting mechanochemical reactions due to the resulting large surface area (10× larger than other materials). We provide the first evidence for H2 production from water reactions with crushed pyrite and suggest that crushed pyrite has a greater influence on subglacial H2O2 production than silicates. We conclude that electron donors in the form of Fe2+ and H2 bursts can be produced in subglacial ecosystems, which may be coupled to substantial concentrations of H2O2 produced from crushed pyrite. This suggests that rock–water mechanochemical reactions may be a greater source of energy for subglacial environments than previously recognised.