【作者】 崔虎雄；

【导师】 成天涛；

【作者基本信息】 复旦大学 ， 环境科学， 2010， 硕士

【摘要】 矿尘是对流层气溶胶的主要成分,主要由Al2O3、Fe2O3、SiO2和CaO等氧化物组成,可以通过直接散射和吸收太阳光对地气辐射收支平衡造成影响。矿尘气溶胶是大气多相反应特性最活跃的气溶胶粒子之一,能够与SO2气体发生非均相化学反应,进而改变矿尘气溶胶的化学组成、光学性质等微观特性。矿尘与海盐气溶胶在大气传输过程中形成的混合气溶胶与SO2反应也会对气溶胶粒子造成类似的影响。迄今为止,有关SO2在矿尘气溶胶表面非均相反应的研究多集中于反应机理等方面,然而其对矿尘粒子光学特性影响的研究相对较少。本文利用傅立叶红外光谱仪、红外漫反射(DRIFTS)及怀特池等实验系统,并结合离子色谱、透射电镜等分析手段和光学理论计算,对SO2在矿尘、矿尘-海盐混合颗粒物表面非均相化学反应导致的硫酸盐生成量及颗粒光学性质变化进行了研究。此外,还采用Xe灯对反应进行照射,模拟太阳光对非均相反应过程及矿尘颗粒光学性质的影响。SO2与矿尘气溶胶典型组分(SiO2、a-Fe2O3、a-Al2O3和CaO)、含铁气溶胶典型代表(a-Fe2O3、Fe3O4、y-Fe2O3和a-FeOOH)非均相化学反应的模拟结果表明,SO2与不同氧化物组分非均相反应对粒子光学特性和硫酸盐生成的影响存在很大的差别,并且SO2与不同氧化物组分非均相反应过程中粒子光学性质剧烈变化仅出现在红外波段800-1300 cm-1。另外,Xe照射对SO2与不同氧化物组分非均相反应有一定的抑制作用。不同反应条件下SO2与a-Fe2O3非均相化学反应的模拟结果显示,温度、SO2和O2浓度对非均相反应产生重要影响。粒子光学性质和硫酸盐生成量随温度的升高而呈现先增加(15-35℃)后减小(35-45℃)的趋势,随SO2浓度(0.51-18.6ppm)的升高呈现增加的趋势,随O2浓度的升高呈现先增加(0%-21%)后减小(21%-40%)的趋势。此外,光学系数和硫酸盐生成量呈现反应初期快速增加、中期递减、后期缓慢减小的变化趋势。SO2与混合气溶胶(a-Fe2O3-NaCl)、(a-Fe2O3-KCl)和(中国黄土样品-NaCl)非均相化学反应的模拟结果显示,粒子光学性质和硫酸盐生成量随混合气溶胶(a-Fe2O3-NaCl)和(a-Fe2O3-KCl)中NaCl、KCl比例的增加而呈现先增加后减小的趋势。对于SO2与纯中国黄土反应,其吸收系数、后向散射系数以及硫酸盐生成量均在Xe灯照射下比无Xe照射大,而SO2与NaCl-中国黄土混合物反应,吸收系数、后向散射系数以及硫酸盐生成量在无Xe灯照射下比Xe照射大。可见Xe灯照射对SO2与中国黄土反应有一定的促进作用,但对SO2与NaCl-中国黄土混合物反应起到一定的抑制效果。更多还原

【Abstract】 Mineral aerosol, one of main components of atmospheric aerosols (including Al2O3, Fe2O3, SiO2, CaO et al) in the troposphere, can impact the climate system by direct radiative forcing through absorbing and scattering solar and terrestrial radiation in the atmosphere, and act as cloud condensation nuclei (CCN) to indirectly influence the optical property and lifetime of clouds. Mineral aerosol can act as one kind of most activated species to react with SO2 and then change their optical properties and chemical composition etc. The similar reactions of SO2 also occour on the particle surface of mineral-sea salt mixture. Until now, the researches of SO2 heterogeneous reaction with aerosols have been mainly focusing on the reaction mechanism. However, studies on the impacts of SO2 heterogeneous reactions on mineral particle optical properties were limited.Combined with Transmission Electronic Microscopy(TEM), Ion Chromatogram (IC) and theory calculation of optical factors, the attempt was afforted to observe the optical variation and sulfate production of gaseous SO2 conversion on mineral aerosol particles using an in suit diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and White cell. In addition, the variation of optical properties and sulfate production in the heterogeneous reaction was also simulated under Xe irradiation.Firstly, the variation of optical properties and sulfate production of gaseous SO2 heterogeneous reactions on typical oxides (SiO2,α-Fe2O3, CaO,α-Al2O3) and Iron oxidants(α-Fe2O3、Fe3O4、γ-Fe2O3和α-FeOOH) was studied using DRIFTS. The results revealed that the changes of optical properties and sulfate pruducts were great different for the heterogeneous reactions of SO2 with above oxides. Furthermore, it was approved that the rapid variation of optical coefficients appeared in the infrared band of 800-1300 cm-1 for the heterogeneous reactions of SO2 on different oxides. It was noted that Xe irradiation showed certain restrained effect to the heterogeneous reaction.Secondly, hematite as the representation of mineral aerosol, the variation of optical properties and sulfate production of the gaseous SO2 reacted on hematite (α-Fe2O3) was studied under different conditions of temperature, SO2 and O2 concentrations. The results revealed that optical properties and sulfate production showed an trend of initial increase and final decreasing with the increasing of temperature and O2 concentration, and an increasing trend with SO2 concentration. In addition, optical coefficients and sulfate production performed an evolution of initial increasing, midterm decreasing and final stabilizing.Finally, NaCl/KCl as the representation of sea salts, the variation of optical properties and sulfate production of the gaseous SO2 on hematite (α-Fe2O3)/Chinese loess-KCl/NaCl mixtures was studied. The results revealed that optical properties and sulfate production showed an trend of initial increasing and final decreasing with the increasing of NaCl/KCl mass fraction in the mixtures of a-Fe2O3-NaCl andα-Fe2O3-KCl. Optical coefficients and sulfate production of SO2 reacted on the Chinese loess were much larger under Xe irradiation than no Xe irradiation, and it was opposite for the SO2 reaction on the mixtures of Chinese loess-NaCl. This also revealed that Xe irradiation restrained the heterogeneous reactions of SO2 on of China loess-NaCl mixtures.更多还原