The lower Venusian atmosphere is the region from the surface to the cloud deck or about 0–50 km. Early modeling studies of the atmosphere were primarily based on thermodynamics; more recent modeling studies are based on kinetics of the elementary reactions. In this paper, we take the accepted nominal composition of near-surface gases at ∼42 km and show some of the constituents are indeed at thermodynamic equilibrium. We impose a small oxygen gradient and use a thermodynamic free energy minimization code to describe the vertical gradients of mixing ratios for the primary gases in the lower atmosphere. The oxygen gradient is within the measurement errors on oxygen and thus maintains mass conservation. Reasonable agreement is found between our calculations and the vertical profiles of H₂O, H₂SO₄, OCS, H₂S, and S_n (n = 1–8). We then did a kinetic analysis of kinetic expressions for the formation of these species. Consistent with other investigators, we find that very few if any reactions should be at equilibrium in the lower atmosphere. Yet our equilibrium calculations do show some agreement with observations. We conclude that the available kinetic expressions likely need improvement and factors such as catalysis must be included to reflect actual Venus conditions.

中文翻译：

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金星下部大气的热力学约束

金星较低的大气层是从地表到云层的区域或大约0–50 km。大气的早期模型研究主要基于热力学。最近的建模研究是基于基本反应的动力学。在本文中，我们采用了在〜42 km处可接受的近地表气体名义组成，并表明其中一些成分确实处于热力学平衡状态。我们施加一个小的氧气梯度，并使用热力学自由能最小化代码来描述低层大气中主要气体的混合比的垂直梯度。氧气梯度在氧气的测量误差范围内，因此保持了质量守恒。在我们的计算与H ₂ O，H ₂的垂直剖面之间找到​​合理的一致性SO ₄，OCS，H ₂ S和S _n（n = 1-8）。然后，我们对形成这些物种的动力学表达进行了动力学分析。与其他研究者一致，我们发现很少有反应在低层大气中达到平衡。然而，我们的平衡计算确实与观察结果有些吻合。我们得出的结论是，可能的动力学表达可能需要改进，并且必须包括诸如催化之类的因素以反映实际的金星状况。