SO2 Oxidation Kinetics Leave a Consistent Isotopic Imprint on Volcanic Ice Core Sulfate
SO2 Oxidation Kinetics Leave a Consistent Isotopic Imprint on Volcanic Ice Core Sulfate
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DOI：
10.1029/2018jd028456
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发表时间：
2018-09-16
影响因子：
4.4
通讯作者：
Farquhar, James
中科院分区：
文献类型：
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作者：
Gautier, Elsa;Savarino, Joel;Farquhar, James
这项工作介绍了对过去2600年南极冰芯记录中火山成因的时间分辨质量独立分馏硫酸盐的测量结果。这些测量用于评估沉积的同位素信号的时间依赖性，并提取现代大气中平流层火山喷发产生硫酸盐的反应的同位素特征。相对于平流层中SO2的快速氧化，雪期（年）信号的时间演化表明，光化学产生的凝聚相在极地冰盖的运输和沉积过程中迅速和连续地与气相分离，并被保存下来。在一些火山喷发中，非零同位素质量平衡突出表明，在运输和/或沉积过程中，部分信号可能会丢失。大量火山事件的研究使得S-33相对于S-36和S-34相对于S-33的斜率分别被限制在-1.56 （1 sigma=0.25）和0.09 （1 sigma=0.02）。S-33与S-36的斜率改进了先前S-36/S-33=-4的测定结果，并与早期地球样品（太古宙）中观测到的硫的范围重叠。然而，在最近的火山成因硫酸盐中，S-33和S-34与太古宙的记录不同。S-36/S-33的相似性和S-33/S-34的差异表明，太古代大气中存在类似的不依赖质量的硫酸盐分馏过程。使用一个简单的模型，我们强调需要几种机制的组合来重现观测到的同位素趋势，并提出现代大气中OH的质量依赖氧化作用的贡献更大。大型火山喷发将含硫气体注入平流层，在那里它们迅速形成硫酸气溶胶。这些气溶胶可以在平流层停留多年，覆盖整个地球，并通过散射和吸收太阳辐射深刻地改变气候。由这一过程形成的硫酸气溶胶获得了一个同位素异常，可以追踪这些过程，并允许在冰芯记录中识别这些喷发，为区分冰芯火山沉积物中高和低气候影响喷发提供了一种手段。这项研究提供了这种随时间变化的同位素特征，用于限制其起源，并了解其产生和演化的过程。
This work presents measurements of time-resolved mass-independently fractionated sulfate of volcanic origin from Antarctic ice core records that cover the last 2,600years. These measurements are used to evaluate the time dependence of the deposited isotopic signal and to extract the isotopic characteristics of the reactions yielding sulfate from stratospheric volcanic eruptions in the modern atmosphere. Time evolution of the signal in snow (years) with respect to the fast SO2 oxidation in the stratosphere suggests that photochemically produced condensed phase is rapidly and continuously separated from the gas phase and preserved during transportation and deposition on the polar ice cap. On some eruptions, a nonzero isotopic mass balance highlights that a part of the signal can be lost during transport and/or deposition. The large number of volcanic events studied allows the S-33 versus S-36 and S-34 versus S-33 slopes to be constrained at -1.56 (1 sigma=0.25) and 0.09 (1 sigma=0.02), respectively. The S-33 versus S-36 slope refines a prior determinations of S-36/S-33=-4 and overlaps the range observed for sulfur seen in early Earth samples (Archean). In recent volcanogenic sulfate, the S-33 versus S-34 differs, however, from the Archean record. The similitude for S-36/S-33 and the difference for S-33/S-34 suggest similar mass-independently fractionated sulfate processes to the Archean atmosphere. Using a simple model, we highlight that a combination of several mechanisms is needed to reproduce the observed isotopic trends and suggest a greater contribution from mass-dependent oxidation by OH in the modern atmosphere.Plain Language Summary Large volcanic eruptions inject sulfurous gases in the stratosphere, where they rapidly form sulfuric acid aerosols. These aerosols can reside in the stratosphere for years, cover the entire globe, and profoundly modify the climate by scattering and absorbing solar radiation. Sulfuric acid aerosols formed by this process acquire an isotopic anomaly that traces these processes and allows identification of these eruptions in ice core records, providing a means to distinguish between high and low climatic impact eruptions in ice core volcanic deposits. This study provides a characterization of this time-dependent isotopic signature that is used to constrain its origin and to understand the processes underlying its production and evolution.