Stable Isotope Geochemistry

硫和氧的非质量依赖（NMD）同位素效应将用于研究地球化学和地球大气演化中的两个主题。 其他人提出，在太古代岩石中硫中观察到的NMD效应是由于在有效的臭氧屏蔽存在之前平流层中的紫外光化学作用。 将在涉及二氧化硫光解的系统实验室实验中研究潜在的光化学。 确定富氧大气形成的时间和机制是生物进化的一个重要因素。第二项研究涉及现代大气，包括在对流层含氧分子中搜索NMD信号，这些分子是从平流层臭氧中获取的，并穿过对流层顶传输。 待分析的样品包括来自低纬度、高海拔冰川的冰芯，这些冰芯可能提供千年来的大气动力学记录。 这两项研究对了解我们大气的化学作用具有实际意义。 这项工作将构成两个研究生的博士论文。

ClaytonEAR-0439925Non-mass-dependent (NMD) isotope effects in sulfur and oxygen will be used to study two topics in the geochemistry and evolution of Earth's atmosphere. It has been proposed by others that the observed NMD effects in sulfur in Archean rocks are due to ultraviolet photochemistry in the stratosphere before the existence of an effective ozone shield. The underlying photochemistry will be studied in systematic laboratory experiments involving photolysis of sulfur dioxide. Determination of the timing and mechanism for the development of an oxygen-rich atmosphere is an important factor in biological evolution. The second study deals with the modern atmosphere, and consists of a search for NMD signals in tropospheric oxygen-bearing molecules, acquired from stratospheric ozone, and transported across the tropopause. Samples to be analyzed include ice cores from low-latitude, high-altitude glaciers, which may provide a millennial record of atmospheric dynamics. Both of these studies are of practical importance in understanding the chemical workings of our atmosphere. This work will constitute the doctoral theses of two graduate students.