首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >Fractal parameters of individual soot particles determined using electron tomography: Implications for optical properties
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Fractal parameters of individual soot particles determined using electron tomography: Implications for optical properties

机译:个人的煤烟颗粒的分形参数决定使用电子断层扫描:对光学性质

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摘要

The morphologies of soot particles are both complex and important. They influence soot atmospheric lifetimes, global distributions, and climate impacts. Particles can have complex geometries with overlapping projecting parts and pores that are difficult to infer from the conventional techniques used to study them. We used electron tomography with a transmission electron microscope (TEM) to determine three-dimensional (3D) properties such as fractal dimension (D f), radius of gyration (R g), volume (V), surface area (A s), and structural coefficient (k a) for individual soot particles from the ambient air of an Asian dust (AD) episode and from a U.S. traffic source. The respective median values of D f are 2.4 and 2.2, of R g are 274 and 251 nm, of A s/V are 9.2 and 13.7 × 10~7 m~(-1), and of k a are 0.67 and 0.71. The corresponding parameters, when calculated from 2D projections such as TEM images, are considerably less precise and commonly erroneous. Unlike other methods that have been used to derive fractal parameters, our method is applicable to particles of any D f. Using the 3D data, we estimate that mass-normalized scattering cross sections of our AD and traffic soot particles are respectively about 15 and 30 times greater than those of unaggregated spheres, which is the shape assumed in global models to estimate radiative forcing. Accurate 3D information can be used to compute more precise optical properties, which are important for estimating direct radiative forcing and improving our understanding of the climate impact of soot.
机译:烟尘粒子的形态都是复杂的和重要的。大气,全球分布,气候的影响。几何图形和投影重叠部分毛孔很难推断的传统的技术用于研究。与传输电子断层扫描使用电子显微镜(TEM)来确定分形等三维(3 d)属性维度(D f)、回转半径(R g),体积(V),表面面积(s)和结构系数(k)个人煤烟颗粒从一个亚洲的环境空气灰尘(广告)事件和美国的流量来源。各自的D f的值中位数是2.4和2.2,R g 274和251海里,s / V 9.213.7×10 ~ 7 m ~(1),和k的是0.67和0.71。相应的参数,当计算从2 d预测TEM图像等大大减少精确和常见的错误。与其他的方法被用来得到分形参数,我们的方法适用于颗粒使用3 D D f。数据,我们估计mass-normalized散射横截面的广告和交通烟尘粒子分别为15和30倍大于未聚合的球体,全球气候模型来估计假定形状辐射强迫。用于计算更精确的光学特性,哪些是重要的评估直接辐射强迫和改善我们的理解气候影响的烟尘。

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