Laboratory Studies of Tropospheric Sulfur Chemistry

近年来，由于需要评估人为产生的硫对酸雨、能见度降低和气候变化等问题的贡献，大气硫循环已成为深入研究的主题。在高度工业化地区，如美国东部和西欧，人为硫量级。然而，在全球范围内，人们认为自然硫排放量与人为来源的排放量大致相等。因此，需要了解自然硫循环，以便建立一个“基线”，与人为扰动进行比较。近年来建立了大量的主要还原硫种CS2、COS和CH3SCH3 （DMS）的测量数据库。旨在确定主要硫氧化途径和量化这些途径的速率的实验室研究也取得了迅速进展。尽管如此，有机硫化合物的大气化学仍然存在着主要的不确定性。本研究旨在阐明控制H2S、CS2、COS、硫醇、硫化物和二硫化物等还原性硫化合物大气氧化的动力学和反应机理。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。一些具体的实验研究将会进行，包括CH2S与O3、HO2和NO2反应的动力学研究，与硫醇、硫化物和二硫化物反应的动力学研究，测定CS2OH+O2反应中SH、CS、S2、HO2、COS、CO和CO2的产率。测定OH和NO3与有机硫化合物反应的CH3S产率，OH和NO3与二甲基亚砜反应的动力学研究，以及通过OH-、NO3-和o -引发的有机硫化合物氧化产生稳定的最终产物SO2、CH3SO3H和（CH3）2SO的机理研究。将采用的实验方法包括耦合激光闪光光解生产不稳定反应物与时间分辨检测中间体和最终产物通过激光诱导荧光，长路紫外可见吸收，或长路红外吸收。大多数实验将在具有温度、压力和气体成分的大气条件下进行。

The atmospheric sulfur cycle has been the subject of intensive investigation in recent years because of the need to assess the contribution of anthropogenically produced sulfur to such problems as acid rain, visibility reduction, and climate modification. In heavily industrialized regions such as the eastern United States and western Europe, anthropogenic sulfur magnitude. On a global scale, however, natural sulfur emissions are thought approximately to equal those from anthropogenic sources. An understanding of the natural sulfur cycle is thus required in order to establish a "base line" with which anthropogenic perturbations can be compared. A substantial measurement data base for the key reduced sulfur species CS2, COS, and CH3SCH3 (DMS) has become available in recent years. Laboratory research aimed at identifying major sulfur oxidation pathways and quantifying the rates of these pathways has also progressed rapidly. Nonetheless, major uncertainties in the atmospheric chemistry of organosulfur compounds remain. This research is aimed at elucidating the kinetics and reaction mechanisms which control the atmospheric oxidation of reduced sulfur compounds, i.e. H2S, CS2, COS, mercaptans, sulfides and disulfides. 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. Some specific experimental investigations which are to be undertaken include kinetics studies of CH2S reactions with O3, HO2, and NO2, kinetics studies of IO reactions with thiols, sulfides, and disulfides, determination of the product yields of SH, CS, S2, HO2, COS, CO, and CO2 from the CS2OH+O2 reaction, determination of CH3S yields from reactions of OH and NO3 with organosulfur compounds, kinetic studies of the reactions of OH and NO3 with dimethylsulfoxide, and investigations of the mechanisms for producing the stable end products SO2, CH3SO3H, and (CH3)2SO via the OH-, NO3-, and IO-initiated oxidations of organosulfur compounds. The experimental methods to be employed involve coupling laser flash photolysis production of unstable reactants with time resolved detection of intermediates and end products by laser induced fluorescence, long path UV-visible absorption, or long path infrared absorption. Most experiments will be carried out under atmospheric conditions of temperature, pressure, and gas composition.