【作者】 吴洪波；

【导师】 陈建民；

【作者基本信息】 复旦大学 ， 环境科学， 2005， 博士

【摘要】 大气颗粒物或气溶胶对大气的辐射和化学组成有着重要影响,许多关键的大气化学过程如臭氧层损耗,酸沉降都与其密切相关。虽然大气颗粒物表面的复相和多相反应是大气反应性物种生成和消除的重要途径,但是由于大气中气体成分复杂而且不同气溶胶粒子的浓度,性质及反应活性具有较大差异,人们对大气中这些气溶胶粒子表面的化学反应过程的认识还十分有限。为了得到大气复相和多相化学反应的信息,对大气中的不同气体成分在不同化学组成的气溶胶粒子表面的化学反应分别进行研究是行之有效的方法。 含硫化合物是典型的大气污染物,而矿尘气溶胶粒子是大气中化学反应特性最活跃的气溶胶粒子之一。因此,研究含硫化合物与矿尘气溶胶粒子及其组成成分的复相化学及复相光化学反应过程具有一定的代表性,对认识大气中含硫化合物的转化过程,揭示大气硫物种转化中气溶胶粒子的贡献有重要的价值。 本文建立了以长光程傅立叶红外光谱为测定基础的原位观测反应体系,并结合x射线光电子光谱（XPS）、漫反射红外光谱（DRIFTS）等分析手段,对大气中主要的含硫化合物二氧化硫（SO₂）,羰基硫（COS）以及二甲基硫（DMS）与矿尘气溶胶典型氧化物组分及大气颗粒物样品的复相（光）化学反应的动力学过程和反应机理进行了研究。 论文首先研究了SO₂与矿尘气溶胶典型氧化物组分及大气颗粒物的复相反应过程,实验证实了SO₂首先在固体表面化学吸附生成SO₃^2-或HSO₃^2-,进而在氧化物表面化学吸附的活性氧和羟基的作用下氧化形成SO₄^2-的反应机理。论文比较了SO₂与不同氧化物反应活性的大小,测定了实际采集的大气颗粒物样品的表观反应速率常数为2.28×10^-5 S^-1,并推断在该反应速率条件下SO₂与大气颗粒物的复相反应可能对大气SO₂的转化有着显著的贡献。 论文重点研究了COS与矿尘气溶胶典型氧化物组分及大气颗粒物的复相反应和光氧化反应过程。一方面,论文发现了常温常压条件下,COS可以与Al₂O₃,Fe₂O₃等氧化物发生显著的作用,并在其表面生成SO₄^2-。通过考察不同酸碱性Al₂O₃的反应,论文证明了氧化物表面的羟基是COS发生反应的决定性因素,因此提出了COS/O₂反应体系中,羟基和表面活性氧共同作用形成SO₄^2-和单质S更多还原

【Abstract】 Atmospheric particles or aerosols play an significant role in atmospheric irradiation balance and changes of chemical components, and many key chemical processes including ozone depletion and acid deposition are known to be concerned with them. Heterogeneous and multiphase reactions on the surface of atmospheric particles are important ways for the production and elimination of atmospheric reactive gases. However, not all of these chemical processes have been known well due to the complexity of gas-phase species, and differences of particle concentrations, surface property and reactivity of condensed-phase species. To obtain more information about these heterogeneous and multiphase processes, it is a routine research approach to investigate the reactions between classified atmospheric trace gases and aerosol particles.Sulfur-containing compounds are the major pollutions in the atmosphere, and mineral dust particles are one of the most active components of aerosols. It is significant to study the heterogeneous reactions between them, for revealing the contribution of atmospheric particles to the conversion of sulfur-containing compounds in the atmosphere.The reaction system based on long optical path FTIR monitoring was established in this work. Combined X-ray Photoelectron Spectroscopy（XPS）, in situ Diffused Reflectance Infrared Fourier Transform Spectroscopy（DRIFTS） and Transmission FTIR, the heterogeneous （photo） reactions between sulfur-containing gases, sulfur dioxide（SO₂）, carbonyl sulfide（COS） and dimethyl sulfide（DMS）, and typical oxides in mineral dust and collected atmospheric particles were investigated, and the reaction mechanisms and kinetics were discussed detailedly in this paper.Firstly, the mechanism of the heterogeneous reaction SO₂/O₂ + Oxides（or particles） was proved to be adsorption of SO₂ on the oxides forming SO₃^2- or HSO₃^2-, and then oxidized into SO₄^2- by hydroxyls and active adsorbed O atoms. The reactivity of different oxides with SO2 was compared, and the apparent reaction rate coefficient of collected atmospheric particles with SO₂ was determined as 2.28×10^-5 s^-1. It can be deduced that the heterogeneous reactions of SO₂ with atmospheric particles may contribute significantly to the conversion of SO₂ in the atmosphere, if the reaction rate coefficient could keep constant under all conditions.更多还原