Wang Ling, Li Zheng-Qiang, Li Dong-Hui, Li Kai-Tao, Tian Qing-Jiu, Li Li, Zhang Ying, Lü Yang, Gu Xing-Fa
International Institute for Earth System Science, Nanjing University, Nanjing 210093, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2012 Jun;32(6):1644-9.
Mineral dust is an important chemical component of aerosol, which has a significant impact on the climate and environmental changes. The spectral behavior of aerosol refractive indices at four wavelengths from 440 to 1 020 nm was analyzed based on one year observation obtained from Beijing AERONET site. The real parts of refractive index (n) in each band did not differ greatly, however the imaginary parts (k) showed a significant difference due to the absorption of mineral dust in aerosol. From 440 to 670 nm k decreased rapidly, while from 670 to 1 020 nm featured a lower, constant value. Accordingly, k(440 nm) could be considered separately with other three bands. Hence, we added mineral dust into the currently used three-component aerosol chemical model to form a new four-component model (i. e. BC, AS, dust and water) which is more suitable to represent the aerosol chemical composition. Then we presented a method to retrieve dust content in aerosols using this four-component model and refractive indices obtained from the sunphotometer measurements. Finally the dust content in aerosol was investigated under different weather conditions, i. e. clear, haze and dust in Beijing. The results showed that volume fractions of the dust component were 88%, 37% and 48% for clear, hazy and dusty day respectively, which was consistent with the coarse mode proportion in aerosols calculated from aerosol size distributions.
矿物尘埃是气溶胶的一种重要化学成分，对气候和环境变化有重大影响。基于在北京AERONET站点获得的一年观测数据，分析了气溶胶在440至1020nm四个波长处的折射率光谱行为。各波段折射率的实部（n）差异不大，但由于气溶胶中矿物尘埃的吸收，虚部（k）表现出显著差异。从440至670nm，k迅速下降，而从670至1020nm呈现较低的恒定值。因此，k（440nm）可与其他三个波段分开考虑。于是，我们将矿物尘埃添加到当前使用的三组分气溶胶化学模型中，形成了一个更适合表示气溶胶化学成分的新的四组分模型（即黑碳、硫酸盐、尘埃和水）。然后，我们提出了一种利用该四组分模型和太阳光度计测量得到的折射率来反演气溶胶中尘埃含量的方法。最后，研究了北京不同天气条件下（即晴天、霾天和沙尘天）气溶胶中的尘埃含量。结果表明，晴天、霾天和沙尘天气下尘埃组分的体积分数分别为88%、37%和48%，这与根据气溶胶粒径分布计算出的气溶胶粗模态比例一致。
