The implications of H2S and H2 kinetic stability in high-T mixtures of magmatic and atmospheric gases for the production of oxidized trace species (e.g., BrO and NOx)
The implications of H2S and H2 kinetic stability in high-T mixtures of magmatic and atmospheric gases for the production of oxidized trace species (e.g., BrO and NOx)
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DOI：
10.1016/j.chemgeo.2008.12.028
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发表时间：
2009-06
期刊：
影响因子：
3.9
通讯作者：
R. S. Martin;T. Roberts;T. Mather;D. Pyle
中科院分区：
文献类型：
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作者：
R. S. Martin;T. Roberts;T. Mather;D. Pyle
以前的研究使用热力学（即，“平衡”）模型来模拟高温岩浆气体在火山口（或类似地，在熔岩穹丘和熔岩湖上）与大气气体混合和反应时发生的成分变化。目前的兴趣是使用这些高T混合物模型的输出，以初始化低T火山羽化学动力学模型。然而，最近的研究表明，某些物种（即，H2S）可能不会在高T混合物中重新平衡。在这项工作中，我们修改了现有的高T混合物模型，将H2S和/或H2视为惰性（即，动力学稳定），同时再平衡所有其它种类。这种修改使我们能够探索H2S和H2动力学稳定性对氧化痕量物质产生的影响，并为低温动力学模型生成更真实的初始化。我们的研究结果表明，如果H2S和H2不重新平衡，高浓度的Br，Cl和OH可能会形成在高T的混合物与少量的大气气体比以前预期的。对于这里考虑的平均岩浆气体组成，我们表明，溴，氯和OH的生产需要一个高T的混合物与~1%的空气，如果H2S不重新平衡和~6%，否则。相比之下，在高T混合物中形成NO需要更大量（>1%）的大气气体，因为混合物中的总N较低。这些结果表明，高T的混合物可能会发挥更重要的作用，在形成氧化的Br和Cl物种比以前认识到的。
Previous studies have used thermodynamic (i.e., “equilibrium”) models to simulate the changes in composition occurring as high-T magmatic gases mix and react with atmospheric gases at volcanic vents (or similarly, in lava domes and on lava lakes). There is current interest in using the outputs of these high-T mixture models to initialize low-T kinetic models for volcanic plume chemistry. However, recent studies have indicated that certain species (i.e., H2S) may not re-equilibrate within the high-T mixture. In this work we modify an existing high-T mixture model to treat H2S and/or H2as inert (i.e., kinetically stable) whilst re-equilibrating all other species. This modification allows us to explore the implications of H2S and H2kinetic stability for the production of oxidized trace species, and to generate more realistic initializations for low-T kinetic models. Our results show that if H2S and H2do not re-equilibrate, high concentrations of Br, Cl and OH may be formed in high-T mixtures with smaller amounts of atmospheric gases than previously anticipated. For the average magmatic gas composition considered here, we show that the production of Br, Cl and OH requires a high-T mixture with ~1% air if H2S does not re-equilibrate and ~6% otherwise. In contrast, the formation of NO in high-T mixtures requires greater amounts (>1%) of atmospheric gases because of low total N in the mixture. These results suggest that high-T mixtures may play a more significant role in the formation of oxidized Br and Cl species than previously recognized.