Effective density (ρ_eff) is an important property describing particle transportation in the atmosphere and in the human respiratory tract. In this study, the particle size dependency of ρ_eff was determined for fresh and photochemically aged particles from residential combustion of wood logs and brown coal, as well as from an aerosol standard (CAST) burner. ρ_eff increased considerably due to photochemical aging, especially for soot agglomerates larger than 100 nm in mobility diameter. The increase depends on the presence of condensable vapors and agglomerate size and can be explained by collapsing of chain-like agglomerates and filling of their voids and formation of secondary coating. The measured and modeled particle optical properties suggest that while light absorption, scattering, and the single-scattering albedo of soot particle increase during photochemical processing, their radiative forcing remains positive until the amount of nonabsorbing coating exceeds approximately 90% of the particle mass.

中文翻译：

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光化学老化引起燃烧气溶胶颗粒的有效密度、形态和光学性质的变化

有效密度 (ρ _eff ) 是描述大气和人体呼吸道中粒子传输的重要属性。在本研究中，确定了住宅燃烧原木和褐煤以及气溶胶标准 (CAST) 燃烧器产生的新鲜和光化学老化颗粒的ρ _eff的粒度依赖性。ρ _eff由于光化学老化而显着增加，特别是对于流动直径大于 100 nm 的烟灰团聚体。增加取决于可冷凝蒸汽和附聚物尺寸的存在，并且可以通过链状附聚物的坍塌和它们的空隙的填充以及二次涂层的形成来解释。测量和建模的粒子光学特性表明，虽然在光化学处理过程中烟灰粒子的光吸收、散射和单次散射反照率增加，但它们的辐射强迫保持正值，直到非吸收涂层的量超过粒子质量的大约 90%。