南京青奥会期间棕碳对大气颗粒物光吸收贡献研究

黑碳 (BC) 和棕碳 (BrC) 是大气中重要的吸光物质。近年来, 大气棕碳光吸收贡献已成为国内外研究热点之一。 2014 年青奥会期间在位于南京江心洲的南京市气象局, 利用三波长光声黑碳光度仪 (PASS-3), 热熔蚀器 (TD), 气溶胶质量分析仪 (APM), 扫描电迁移率粒径谱仪 (SMPS) 和空气动力学粒径谱仪 (APS) 进行了大气实时观测。基于Mie 模型和 AAE 方法, 计算得出 BrC 在 405 nm 和 532 nm 处的平均光吸收系数分别为 (8.5±4.5) Mm−1 和 (3.2±2.1)Mm−1, 相应的平均光吸收贡献分别为 (22.7±12.0)% 和 (13.6±9.2)%, 说明 BrC 的光吸收能力具有波长依赖性。进而对核-壳和外混两种模型中 αBC 随复折射指数变化做了敏感性分析。在这两种模型中, αBC 均对 BC 核复折射指数虚部最为敏感, 其次是 BC 核复折射指数的实部; 不同的是, 在外混模型中非吸光物质复折射指数实部的改变不会影响 αBC。

Contribution of Brown Carbon to Light Absorption of Atmospheric Particles During Nanjing Youth Olympic Games

Black carbon (BC) and brown carbon (BrC) are important light absorbers in the atmosphere. Recently, thecontribution of atmospheric brown carbon to light absorption has become one of the research hotspots at home andabroad. During the 2014 Nanjing Youth Olympic Games, a real-time atmospheric observation was carried out usingthree-wavelength photoacoustic soot photometer (PASS-3), thermal denuder (TD), aerosol particle mass analyzer(APM), scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) at Nanjing MeteorologicalBureau (32.06◦ N, 118.70◦ E) on Jiangxin Island of Nanjing, China. Based on Mie model and AAE method,the average light absorption coefficients of BrC at 405 and 532 nm were calculated to be (8.5±4.5) Mm−1 and(3.2±2.1) Mm−1, respectively, and the corresponding average light absorption contributions were (22.7±12.0)%and (13.6±9.2)%, indicating that the light absorption capacity of BrC is wavelength dependent. Furthermore, thesensitivity analysis of αBC with the change of refractive index in the core-shell model and external model wasconducted. It is shown that in both models, αBC is the most sensitive to the imaginary part of the refractive index ofBC core, followed by the real part of the refractive of BC core. While the difference is that in the external mixingmodel, the change of the real part of the refractive index of the non-light-absorption material does not affect theαBC.