Laboratory Studies of Tropospheric Sulfur Chemistry

大气硫循环多年来一直是环境科学家非常感兴趣的课题，因为需要评估生物和人为硫对酸雨、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，人为硫排放超过自然排放约一个数量级。然而，在全球范围内，生物源硫排放被认为与人为源硫排放大致相等。因此，需要了解生物硫循环，以便建立一个基线，与人为干扰进行比较。该研究计划为期三年，包括持续的实验室研究，旨在阐明控制还原性硫化合物大气氧化的动力学和反应机制。强调“实时”直接观察反应中间体和相对稳定的产物，因为只有通过这样的观察才能获得具有独特解释的结果。将采用的实验方法包括耦合激光闪光光解产生的不稳定反应，通过激光诱导荧光、原子共振荧光、长路紫外可见吸收或可调谐二极管激光（红外）吸收对中间体和最终产物进行时间分辨检测。只要有可能，实验将在具有温度、压力和气体成分的大气条件下进行。

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.