Ultraviolet refractive index values of organic aerosol extracted from deciduous forestry, urban and marine environments
Ultraviolet refractive index values of organic aerosol extracted from deciduous forestry, urban and marine environments
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从落叶林、城市和海洋环境中提取的有机气溶胶的紫外折射率值
DOI：
10.1039/d3ea00005b
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Barker C
中科院分区：
文献类型：
--
作者：
Barker C
大气气溶胶的折射率值需要解决大气辐射强迫大小的大不确定性，并且从大气中采样的颗粒物的折射率色散与波长的测量在紫外波长上是罕见的。一个紫外优化的光谱系统照亮光学捕获的单个粒子从对流层环境的范围，以确定粒子的光学特性。来自偏远海洋、受污染的城市和林业环境的气溶胶被收集在石英过滤器上，有机部分被提取并雾化以形成微米级的球形颗粒。在0.320-0.480 μm的近紫外-可见光范围内，测量了光阱粒子的半径和折射率色散随波长变化的真实的分量，测量精度分别为0.001 μm和0.002。远距离海洋气溶胶的折射率最低（n = 1.442（λ = 0.350 μm）），冠层以上的乡村森林气溶胶（n = 1.462-1.481（λ = 0.350 μm））和污染的城市气溶胶（n = 1.444-1.485（λ = 0.350 μm））的折射率随波长的色散相似。林冠内气溶胶折射率最高（n = 1.508（λ = 0.350 μm））。该研究首次对0.350 μm以下大气气溶胶样品的折射率随波长的色散进行了单粒子测量。柯西色散方程，通常用来描述气溶胶粒子的可见光折射率的变化，被证明扩展到紫外波长低于0.350 μm的城市，森林和大气气溶胶水不溶性提取物从这些环境。一维辐射传输计算的大气核壳矿物气溶胶与这种材料的膜和没有这种材料之间的大气层顶部的CO2的差异证明了有机膜形成的矿物气溶胶的重要性。
The refractive index values of atmospheric aerosols are required to address the large uncertainties in the magnitude of atmospheric radiative forcing and measurements of the refractive index dispersion with wavelength of particulate matter sampled from the atmosphere are rare over ultraviolet wavelengths. An ultraviolet-optimized spectroscopic system illuminates optically-trapped single particles from a range of tropospheric environments to determine the particle's optical properties. Aerosol from remote marine, polluted urban, and forestry environments is collected on quartz filters, and the organic fraction is extracted and nebulized to form micron-sized spherical particles. The radius and the real component of refractive index dispersion with wavelength of the optically trapped particles are determined to a precision of 0.001 μm and 0.002 respectively over a near-ultraviolet-visible wavelength range of 0.320–0.480 μm. Remote marine aerosol is observed to have the lowest refractive index (n = 1.442 (λ = 0.350 μm)), with above-canopy rural forestry aerosol (n = 1.462–1.481 (λ = 0.350 μm)) and polluted urban aerosol (n = 1.444–1.485 (λ = 0.350 μm)) showing similar refractive index dispersions with wavelength. In-canopy rural forestry aerosol is observed to have the highest refractive index value (n = 1.508 (λ = 0.350 μm)). The study presents the first single particle measurements of the dispersion of refractive index with wavelength of atmospheric aerosol samples below wavelengths of 0.350 μm. The Cauchy dispersion equation, commonly used to describe the visible refractive index variation of aerosol particles, is demonstrated to extend to ultraviolet wavelengths below 0.350 μm for the urban, forestry, and atmospheric aerosol water-insoluble extracts from these environments. A 1D radiative-transfer calculation of the difference in top-of-the-atmosphere albedo between atmospheric core–shell mineral aerosol with and without films of this material demonstrates the importance of organic films forming on mineral aerosol.