This study analyzes the spectral characteristics of in situ measured aerosol properties, namely scattering, absorption and single scattering albedo (SSA), explicitly examining the curvature characteristics of their wavelength dependence. Measurements were performed at an urban background site in Athens, Greece, during December 2017 and March 2018 characterized by contrasting aerosol sources and types, i.e. residential wood burning (RWB) and desert dust, respectively, which modulate the urban conditions, that are typically dominated by fossil-fuel combustion. Aerosol types were classified via the Scattering Ångström Exponent (SAE) vs. Absorption Ångström Exponent (AAE) matrix, with the black carbon (BC)-dominated type displaying the highest fraction (~40%) in both periods. The spectral optical properties were examined for each aerosol type and month, revealing notable differences, which are closely linked to the contrasting emission sources, atmospheric dynamics and mixing processes. BC from fossil-fuel emissions and regional background aerosols mostly presented similar characteristics in both months. Emphasis was given on the spectral curvature effect, since the different aerosol types display notable changes in the spectral dependence of scattering and absorption in logarithmic coordinates. The enhanced presence of brown carbon resulted in negative curvature for scattering (concave curves) and highly positive for absorption (convex curves), while the presence of BC was mostly translated in a better fit of the Ångström formula and small curvature effects. Intense dust events resulted in positive curvature for absorption and mostly negative for scattering. A scatterplot between the wavelength dependence of SSA and the scattering curvature may further differentiate key aerosol types i.e. BC, brown carbon and dust. This study highlights the curvature effects of the scattering, absorption and SSA, which have not been adequately addressed yet. The approach provides new insights in the differentiation of source-related aerosol types, although more analysis is needed to examine if findings are reproduced in other environments.

本研究分析了原位测量的气溶胶特性的光谱特征，即散射、吸收和单次散射反照率 (SSA)，明确检查了它们的波长依赖性的曲率特征。测量是在 2017 年 12 月和 2018 年 3 月期间在希腊雅典的一个城市背景地点进行的，其特征是气溶胶来源和类型不同，即分别调节城市条件的住宅木材燃烧 (RWB) 和沙漠粉尘，这通常占主导地位通过化石燃料燃烧。气溶胶类型通过散射 Ångström 指数 (SAE) 与吸收 Ångström 指数 (AAE) 矩阵进行分类，其中以黑碳 (BC) 为主的类型在两个时期都显示出最高的分数 (~40%)。检查了每种气溶胶类型和月份的光谱光学特性，揭示了显着差异，这与对比排放源、大气动力学和混合过程密切相关。来自化石燃料排放和区域背景气溶胶的 BC 在这两个月中大多呈现出相似的特征。重点是光谱曲率效应，因为不同的气溶胶类型在对数坐标中散射和吸收的光谱依赖性显示出显着变化。棕色碳的增强存在导致散射的负曲率（凹曲线）和吸收的高正曲率（凸曲线），而 BC 的存在主要转化为更好地拟合 Ångström 公式和小曲率效应。强烈的尘埃事件导致吸收的正曲率和散射的大部分负曲率。SSA 的波长相关性和散射曲率之间的散点图可以进一步区分关键的气溶胶类型，即 BC、棕碳和灰尘。这项研究突出了散射、吸收和 SSA 的曲率效应，这些效应尚未得到充分解决。该方法为区分与源相关的气溶胶类型提供了新的见解，尽管需要更多的分析来检查发现是否在其他环境中重现。尚未得到充分解决。该方法为区分与源相关的气溶胶类型提供了新的见解，尽管需要更多的分析来检查发现是否在其他环境中重现。尚未得到充分解决。该方法为区分与源相关的气溶胶类型提供了新的见解，尽管需要更多的分析来检查发现是否在其他环境中重现。