CO2 Removal With Enhanced Weathering and Ocean Alkalinity Enhancement: Potential Risks and Co-benefits for Marine Pelagic Ecosystems
CO2 Removal With Enhanced Weathering and Ocean Alkalinity Enhancement: Potential Risks and Co-benefits for Marine Pelagic Ecosystems
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DOI：
10.3389/fclim.2019.00007
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发表时间：
2019-10-11
影响因子：
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通讯作者：
Renforth, Phil
中科院分区：
文献类型：
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作者：
Bach, Lennart T. T.;Gill, Sophie J. J.;Renforth, Phil
到21世纪末，人类需要从大气中去除数千亿吨的二氧化碳，才能在全球碳预算的限制下将全球变暖控制在2摄氏度以下。然而，目前尚不清楚这是否以及如何实现。一个被广泛认可的想法是加速矿物的风化反应，当它们溶解时消耗二氧化碳。加速可以通过粉碎并将这些矿物分布到陆地（称为“增强风化（EW）”）或海洋（称为“海洋碱度增强（OAE）”）来实现，从而大大增加其活性表面。然而，在溶解过程中，大气二氧化碳的预期消耗将不可避免地伴随着矿物溶解产物（碱度、Si、Ca、Mg、Fe、Ni等）的释放。在这里，我们估计了它们的最大添加量，以评估它们对远洋群落（主要是初级生产者）和它们控制的生物地球化学通量的潜在影响。基于这一评估，我们初步确定了诱发正面和/或负面副作用的可能性，对Fe， Ni， Si来说是高的，对碱度来说是中等的，对Ca和Mg来说是低的。然而，在扰动热点处，微扰电位总是较高的，并且电子束与声发射的微扰电位不同。此外，EW/OAE的生态/生物地球化学后果在很大程度上取决于所使用的矿物。我们假设，主要的钙化剂将有利于方案，其中CaCO3衍生物将被使用，由于在碳酸盐化学有益的变化。打个比方，这可能会把蓝海变成白海。当使用硅酸盐时，额外的Si， Fe和Ni的释放可以有利于硅化剂和n -2固定剂（蓝藻），并提高海洋生产力，最终将蓝海变成绿色（er）海洋。这些考虑要求进行专门的研究，以评估矿物溶解产品对海洋和其他环境的风险和共同利益。事实上，EW和OAE都可以成为在全球范围内实现二氧化碳去除的重要工具，但在决定实施它们之前，应该揭示相关的风险和/或协同效益。
Humankind will need to remove hundreds of gigatons of carbon dioxide (CO2) from the atmosphere by the end of the twenty-first century to keep global warming below 2 degrees C within the constraints of the global carbon budget. However, so far it is unclear if and how this could be achieved. A widely recognized idea is to accelerate weathering reactions of minerals that consume CO2 when they dissolve. Acceleration could be realized by pulverizing and distributing gigatons of these minerals onto land (termed "enhanced weathering (EW)") or sea (termed "ocean alkalinity enhancement (OAE)") thereby largely increasing their reactive surfaces. However, the desired consumption of atmospheric CO2 during dissolution would inevitably be accompanied by a release of mineral dissolution products (alkalinity, Si, Ca, Mg, Fe, Ni, and maybe others). Here, we approximate their maximum additions to assess potential consequences for pelagic communities (mainly primary producers) and the biogeochemical fluxes they control. Based on this assessment, we tentatively qualify the potential to induce positive and/or negative side effects to be high for Fe, Ni, Si, intermediate for alkalinity, and low for Ca and Mg. However, perturbation potentials are always higher at perturbation hotspots and would be different for EW than for OAE. Furthermore, ecological/biogeochemical consequences of EW/OAE largely depend on the minerals used. We hypothesize that mainly calcifiers would profit in a scheme where CaCO3 derivatives would be used due to beneficial changes in carbonate chemistry. Figuratively, this may turn the blue ocean into a white(r) ocean. When using silicates, the release of additional Si, Fe and Ni could benefit silicifiers and N-2-fixers (cyanobacteria) and increase ocean productivity ultimately turning the blue ocean into a green(er) ocean. These considerations call for dedicated research to assess risks and co-benefits of mineral dissolution products on marine and other environments. Indeed, both EW and OAE could become important tools to realize CO2 removal at the planetary scale but associated risks and/or co-benefits should be revealed before deciding on their implementation.