Laboratory Studies of Tropospheric Sulfur Chemistry

多年来，大气硫循环一直是环境科学家非常感兴趣的课题，因为需要评估生物硫和人为硫对酸雨、能见度降低和气候变化等问题的贡献。在美国东部和欧洲大部分地区等高度工业化地区，人为硫排放比自然排放高出约一个数量级。然而，在全球范围内，生物来源的硫排放量被认为与人为来源的排放量大致相当。因此，需要了解生物成因的硫循环，以便确定可与人为扰动进行比较的基线。这项研究计划为期三年，包括持续的实验室研究，旨在阐明控制还原硫化合物在大气中氧化的动力学和反应机理。强调“实时”地直接观察活性中间体和相对稳定的产物，因为只有通过这种观察才能得到具有独特解释的结果。实验方法包括利用激光诱导荧光、原子共振荧光、长程紫外可见吸收或可调谐半导体激光(红外)吸收，将不稳定反应的激光闪光光解产物与中间体和最终产物的时间分辨检测相结合。只要有可能，实验将在温度、压力和气体组成的大气条件下进行。

The atmospheric sulfur cycle has been a subject of intense interest to environmental scientists for many years because of the need to assess the contributions of biogenic and anthropogenic sulfur to such problems as acid rain, visibility reduction, and climate modification. In heavily industrialized regions such as the eastern United States and much of Europe, anthropogenic sulfur emissions exceed natural emissions by about an order of magnitude. On a global scale, however, biogenic sulfur emissions are thought to approximately equal those from anthropogenic sources. An understanding of the biogenic sulfur cycle is thus required in order to establish a baseline against which anthropogenic perturbations can be compared. This research program is three years in duration and involves continued laboratory studies aimed at elucidating the kinetics and reaction mechanisms which control the atmospheric oxidation of reduced sulfur compounds. Direct observation of reactive intermediates and relatively stable products in "real time" is emphasized because only through such observations can results with a unique interpretation be obtained. The experimental methods to be employed involve coupling laser flash photolysis production of unstable reactions with time-resolved detection of intermediates and end products by laser induced fluorescence, atomic resonance fluorescence, long path UV-visible absorption, or tunable diode laser (infrared) absorption. Whenever possible, experiments will be carried out under atmospheric conditions of temperature, pressure, and gas composition.