【作者】 于兴娜；

【导师】 陈建民； 成天涛；

【作者基本信息】 复旦大学 ， 环境科学， 2008， 博士

【摘要】 与温室气体相比，大气气溶胶辐射强迫的估算更加复杂和不确定，主要原因在于气溶胶的辐射强迫机制非常复杂以及缺乏对其微观特性的系统观测。东亚作为世界沙尘天气的多发区之一，而我国沙尘气溶胶的研究还处于起始阶段。鉴于东亚地区气溶胶在气候变化中的重要地位，本论文利用AERONET资料和前人研究结果对东亚地区大气气溶胶的物理、化学及光学特性进行了详细分析，从气候学的角度对比分析了沙尘天气发生期间沙尘源区与下游地区气溶胶的微物理特性差异，对中国北方气溶胶的微物理特性做了详细的研究，同时对矿尘气溶胶在远程传输过程中光学特性的变化进行了实验模拟和初步探讨。本论文主要包括以下五部分内容。第一部分主要利用前人研究结果系统分析比较了东亚地区大气气溶胶粒子的物理、化学及光学特性。中国北方地区PM_2.5、水溶性离子、有机物（如PAHs、OC、EC）以及部分元素浓度冬季高于夏季，而且通常高于南方以及日韩地区。同时，沿海和污染地区的PM_2．5、PAHs、OC、EC浓度以及气溶胶光学厚度（AOT）和埃斯屈朗波长指数（α）都高于清洁地区；而沿海站点的Na⁺、SO₄^2-、Mg²⁺和Cl^-浓度也较高。第二部分利用前人研究结果总结了东亚地区沙尘气溶胶粒子的微观特性。沙尘气溶胶的质量浓度、水溶性Ca²⁺和Na⁺、地壳元素Al、Ca、Fe等均呈现出自西向东递减的趋势：沙尘源区的气溶胶粒子通常具有高的AOT和SSA以及低α：而下游地区常表现为高的AOT和α以及低SSA。污染城市和沿海地区SO₄^2-、NO₃^-和Cl^-具有较高的浓度。第三部分利用AERONET观测资料从气候学的角度分析了东亚地区沙尘天气发生时沙尘源区与下游区气溶胶微物理特性的差异。与日韩站相比，中国站具有更高的AOT和更低的α，当沙尘暴出现时α会降到零甚至负值。体积尺度谱分布为三模态结构，中国站的积聚态半径集中在0．07μm，两个粗模态半径分别为1．3和2．9-3．8μm；日韩站的依次为0．09，1．3-2．2和2．9-3．8μm。在波长440-1020nm时中国站的SSA为0．95，韩国和日本站分别为0．92和0．95：中国站的复折射指数实部为1．51，韩国和日本站分别为1．45和1．39，中国和日韩站的虚部分别为0．0015-0．0044和0．0018-0．0052；所有站点的平均散射不对称因子可以看作0．67。第四部分针对中国北方大气气溶胶的微物理特性进行了详细分析。春季沙尘源区以及夏季污染严重的地区均具有较高的AOT。气溶胶粒子谱分布为三模态结构，即半径为0．07-0．15μm的积聚态，1．3-1．7和3．8-5．0μm的两个粗模态；在波长440-1020nm时，冬半年粗粒子和细粒子的SSA分别为0．85和0．94，夏半年的为0．73和0．86：全年粗粒子和细粒子的散射不对称因子分别为0．79和0．58；沙尘源区和下游区的实部分别为1．40-1．54和1．45-1．55；另外，散射相函数也随散射角度的不同而不同，在120°时相函数通常达到最低。第五部分通过红外漫反射（DRIFTS）实验模拟了铁氧化物在不同温度、与海盐不同比例混合、不同氧气和SO₂浓度条件下表面多相反应引起颗粒吸收与后向散射系数的变化情况。SO₂与α-Fe₂O₃发生多相反应后的吸收和后向散射系数明显高于其它氧化物的反应。反应温度不同吸收和后向散射系数的眼部情况也不同。对于SO₂与不同比例的α-Fe₂O₃和NaCl混合物多相反应引起的颗粒特性变化而言，50-70％比例混合的混合物通常要高于其他混合比例的混合物；不同SO₂和O₂浓度时反应前后混合物颗粒的吸收和后向散射系数也有差异。更多还原

【Abstract】 The estimation of radiative forcing to atmospheric aerosols is considered more complex and larger uncertainties than greenhouse gases. This situation is mainly due to the complexity of aerosol radiative forcing mechanism and the lack of detailed information of aerosol properties, such as size distribution, chemical composition, atmospheric transport and removal processes, etc. East Asia is one of the major sources of wind-blown dust in the world, however, up to date the studies on the dust aerosol from this region are far from completeness. The objective of this study is to characterize and compare the physical, chemical and optical properties of aerosols emitted from East Asia in different seasons, especially in dust events. Moreover, the optical properties of aging mineral particles which transported from source areas to remote downwind regions e.g. ocean etc., because of SO₂ uptake and thus heterogeneous reaction on the surfaces of dust and their mixture with sea salt, were simulated in a laboratory facility.The content mainly includes 5 parts, as following:PartⅠ. The physical, chemical and optical characteristics of aerosols in East Asia were summarized and analyzed through the published data of previous researches. PM_2.5, water-soluble ion, organic compounds （such as PAHs, OC and EC） and chemical element concentrations in northern China were higher than southern China, Korea and Japan, commonly higher in winter than summer. PM_2.5, PAHs, OC and EC concentrations in polluted regions were larger than clean and coastal regions, and the Na⁺, SO₄^2-, Mg²⁺ and Cl^- concentrations of coastal regions showed a higher value. Higher AOT and a occurred in polluted regions but clean regions.PartⅡ. The physical, chemical and optical properties of dust aerosols were analyzed by the published data of former researches. The concentrations of mass, Ca²⁺, Na⁺ and element components showed a decreasing trend from west to east in East Asia. The concentrations of SO₄^2-,NO₃^- and Cl^- also showed a higher value in both polluted and coastal regions. Higher AOT and SSA occurred in dust source regions other than downwind regions, associated with lowerα.PartⅢ. A comparison of dust properties was performed between Chinese continent as source regions and Korea, Japan as downwind regions during dust events. Higher AOT appeared at Chinese sites than Korean and Japanese sites associated with lowerα. The value ofαdecreased with increasing AOTs, and decreased to zero or negative when heavy dust events occurred especially in source regions. The aerosol volume size distributions showed a tri-modal structure, one accumulation mode with median radius 0.07μm and two coarse modes with radii 1.3, 2.9-3.8μm in source regions, and one accumulation mode with radius 0.09μm and two coarse modes with radii 1.3-2.2μm and 2.9-3.8μm in downwind regions. In view of climate, SSA at 440, 670, 870 and 1020 nm was about 0.95 in source regions of China, and 0.92 in downwind regions of Korea and 0.95 of Japan. The real parts of refractive index were 1.51 in China, and 1.45 in Korea and 1.39 in Japan, but the imaginary parts had values of 0.0015-0.0044 in source regions and 0.0018-0.0052 in downwind regions. The asymmetry factors were about 0.67 over source and downwind regions.PartⅣ. The climatology of aerosol microphysical properties in northern China was examined from 2001 to 2005. High AOTs occurred at dust source regions in spring or at serious polluted regions in summer. The aerosol size distributions showed a tri-modal structure, one accumulation mode with radius 0.07-0.15μm and two coarse modes with radii 1.3-1.7 and 3.8-5.0μm. SSA showed a low sensitivity to AOTs at the four wavelengths of 440, 670, 870 and 1020 nm, about 0.94 for fine particles （r<0.6μm） and 0.85 for coarse particles （r>0.6μm） in winter and spring, and 0.86 for fine particles and 0.73 for coarse particles in summer and autumn. The asymmetry factor was 0.58 for fine particles and 0.79 for coarse particles in all seasons. The scattering phase functions varied with scattering angles, with the minimum occurred at 120°.PartⅤ. The particle optical property variation for heterogeneous reaction of SO₂ on iron oxides and hematite-NaCl mixture was investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS）. After heterogeneous reactions, the absorption and backward scattering coefficients of hematite are higher than those of other iron oxides, and varied with reaction temperature. The absorption and backward scattering coefficients are commonly higher in hematite mixture with 50-70% NaCl than pure hematite and other mixtures, and larger magnitudes at high SO₂ concentration than low SO₂ concentration. Under reactions of 1-10% O₂ concentrations, the absorption and backward scattering coefficients are in a higher increase than those of 20-30% O₂ concentrations.更多还原