科研之友
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摘要
An idealized spherical model with black carbon (BC) aggregates fully coated by sulfate is developed to study the absorption enhancement (E-ab) of polydisperse BC aerosols, which is numerically calculated by the multiple-sphere T-matrix method (MSTM). The aim of this study is to evaluate the effects of aerosol microphysics on the absorption enhancement of fully coated BC particles. The Eat values of accumulation concentric coated BC aggregates with different BC fractal dimensions vary within 2%, while those of coarse coated BC aggregates can alter up to 20% depending on shell-core ratio D-p/D-c, (spherical equivalent particle diameter divided by BC core diameter). The BC position inside coating can result in an E-ab decrease of fully coated BC aggregates up to approximately 15% and 20% in the accumulation and coarse modes, respectively. Compared with the concentric spherical structure, the off-center coated BC aggregates shows similar E-ab with a difference less than 9% in the accumulation mode, whereas it can lead to up to 31% reductions in Eat in the coarse mode. The absorption enhancement of aged BC is sensitive to particle size distribution, and it decreases as particles becomes larger in accumulation mode, whereas the reverse is true in coarse mode. For BC aggregates fully coated with a very thin layer sulfate at different size distributions, E-ab values are generally in ranges of 1.5-1.8 and 1.3-1.4 in accumulation and coarse modes, respectively, while with coating reaching D-p/D-c=2.7, their values range from 1.7-2.4 and 2.0-2.1 in accumulation and coarse modes, respectively. Our study indicates that, larger D-p/D-c with BC aggregates not close to the coating boundary, or BC position closer to particle geometric center enhance BC lensing effect, whereas BC aggregates near the boundary of heavy coating may not further enhance lensing effect significantly with increased coating fraction.
- 出版日期2017-11
- 单位南京信息工程大学
