Shapes of soot aerosol particles and implications for their effects on climate
Shapes of soot aerosol particles and implications for their effects on climate
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DOI：
10.1029/2009jd012868
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发表时间：
2010-08-14
影响因子：
4.4
通讯作者：
Buseck, Peter R.
中科院分区：
文献类型：
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作者：
Adachi, Kouji;Chung, Serena H.;Buseck, Peter R.
煤烟气溶胶颗粒（也称为吸光碳、黑碳或元素碳）通过吸收太阳辐射而成为全球变暖的主要因素。当嵌入有机物或硫酸盐中时，如在墨西哥城（MC）和其他特大城市等污染地区常见的那样，它们的光学特性受到其形状和在宿主颗粒中的位置的影响。然而，关于这些变量以及它们如何影响烟尘造成的变暖，仍然存在很大的不确定性。使用电子断层扫描与透射电子显微镜，三维（3-D）图像的个别烟尘颗粒嵌入主机颗粒收集MC及其周围环境。从这些3-D图像，我们使用离散偶极子近似计算的光学性质。许多煤烟颗粒具有开放的链状形状，即使在被有机物质包围后也是如此，并且位于其主体材料内的偏离中心的位置。这种嵌入的烟尘吸收阳光的效率低于如果紧凑和位于其主体颗粒的中心附近。在我们的MC样本的情况下，它们对直接辐射强迫的贡献比它们具有简单的核壳形状（这是许多气候模型中假设的形状）的情况下小20%。这项研究表明，在其主机粒子的煤烟的形状和位置有一个重要的影响粒子的光学性质，并应被视为潜在的重要变量时，评估全球气候变化。
Soot aerosol particles (also called light-absorbing, black, or elemental carbon) are major contributors to global warming through their absorption of solar radiation. When embedded in organic matter or sulfate, as is common in polluted areas such as over Mexico City (MC) and other megacities, their optical properties are affected by their shapes and positions within their host particles. However, large uncertainties remain regarding those variables and how they affect warming by soot. Using electron tomography with a transmission electron microscope, three-dimensional (3-D) images of individual soot particles embedded within host particles collected from MC and its surroundings were obtained. From those 3-D images, we calculated the optical properties using a discrete dipole approximation. Many soot particles have open, chainlike shapes even after being surrounded by organic matter and are located in off-center positions within their host materials. Such embedded soot absorbs sunlight less efficiently than if compact and located near the center of its host particle. In the case of our MC samples, their contribution to direct radiative forcing is similar to 20% less than if they had a simple core-shell shape, which is the shape assumed in many climate models. This study shows that the shapes and positions of soot within its host particles have an important effect on particle optical properties and should be recognized as potentially important variables when evaluating global climate change.