The Measurement of Mass Independent Isotopic Compositions in Atmospheric Species as a New Index of Global Processes

9711203 Thiemens这个项目包括大气二氧化碳、分子氧、水和大小分离的硫酸盐气溶胶的稳定同位素测量（氧、硫）。这些测量区分了质量依赖和独立的同位素组成，作为诊断探针，可用于诸如二氧化碳和臭氧之间的光化学耦合、全球碳循环库转移、平流层-对流层和平流层-中间层混合以及硫酸盐气溶胶来源和转化机制等现象。全球采样计划将利用地面、船上和飞机，以及平流层气球和火箭收集。平流层和中间层二氧化碳具有较大的不依赖质量的氧同位素组成，这是由单线态原子氧相互作用产生的，其丰度不易测量。将继续进行高层大气测量，以确定这种同位素变化的定量来源以及季节和空间变化。在与国际科学家的合作下，将从平流层气球、商业飞机货舱中的采样系统和火箭中获取样本。早些时候由火箭收集的水样本将被分析为稳定的氧同位素，这将提供关于平流层水来源的信息。来自原位甲烷氧化的水应保持与臭氧质量无关的组成，而来自对流层的水则依赖于质量。平流层中二氧化碳（与质量无关）获得的异常同位素特征特别标记了对流层（与质量有关）二氧化碳。因此，二氧化碳的同位素测量，结合宇宙起源的硫核素的同时测量，可以确定平流层入侵。二氧化碳样本将从拉霍亚、北极、南极、印度和印度洋上的船只等多个地面观测站获得。硫酸盐气溶胶将被收集成六种大小的组分，并对所有三种氧和所有四种硫稳定同位素进行分析。同位素特征可能反映了均相或非均相氧化途径。硫同位素也将部分确定其来源。雨水样本将被收集，硫酸盐将被分析。将测量一种短寿命的宇宙核素，以确定硫氧化物的相对年龄和沉积速度。

9711203 Thiemens This project consists of stable isotope measurements (oxygen, sulfur) of atmospheric carbon dioxide, molecular oxygen, water, and size separated sulfate aerosols. These measurements distinguish mass dependent and independent isotopic compositions as a diagnostic probe of such phenomena as the photochemical coupling between carbon dioxide and ozone, the global carbon cycle reservoir transfer, stratosphere-troposphere and stratosphere-mesosphere mixing, and sulfate aerosol sources and transformation mechanisms. A global sampling program will utilize ground, shipboard, and aircraft-based, as well as stratospheric balloon and rocket collection. Stratospheric and mesospheric carbon dioxide possesses a large and variable mass independent oxygen isotopic composition, which derives from interaction with singlet atomic oxygen, whose abundance is not easily measurable. Upper atmospheric measurements will be continued to determine the quantitative source of this isotopic variation and the seasonal and spatial variations. In collaboration with international scientists, samples will be obtained from stratospheric balloons, a sampling system in the cargo hold of a commercial aircraft, and rockets. Water from samples collected earlier by rockets will be analyzed for stable oxygen isotopes, which will provide information on the sources of stratospheric water. Water from in situ methane oxidation should maintain the ozone mass independent composition, whereas water from the troposphere is mass dependent. The anomalous isotopic characteristic acquired by carbon dioxide (mass independent) in the stratosphere specifically tags it with respect to tropospheric (mass dependent) carbon dioxide. Therefore, isotopic measurements of carbon dioxide, combined with simultaneous measurements of a cosmogenic sulfur nuclide, allow the identification of stratospheric incursions. Carbon dioxide samples will be obtained from various ground-based stations including La Jolla, the Arctic, Antarctic, India, a nd on ships in the Indian ocean. Sulfate aerosols will be collected in six size fractions and analyzed for all three oxygen and all four sulfur stable isotopes. The isotopic signature possibly reflects homogenous vs. heterogeneous oxidation pathways. The sulfur isotopes will also partly define sources. Rain samples will be collected and the sulfate analyzed. A short lived cosmogenic nuclide will be measured to determine the relative age and deposition velocity of sulfur oxides.