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首页> 外文期刊>Atmospheric chemistry and physics >Amplification of black carbon light absorption induced by atmospheric aging: temporal variation at seasonal and diel scales in urban Guangzhou
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Amplification of black carbon light absorption induced by atmospheric aging: temporal variation at seasonal and diel scales in urban Guangzhou

机译：大气老化引起的黑碳光吸收的扩增：广州市季节性和DIEL秤的时间变化

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摘要

Black carbon (BC) aerosols have been widely recognized as a vital climate forcer in the atmosphere. Amplification of light absorption can occur due to coatings on BC during atmospheric aging, an effect that remains uncertain in accessing the radiative forcing of BC. Existing studies on the absorption enhancement factor (Eabs) have poor coverage on both seasonal and diurnal scales. In this study, we applied a recently developed minimum R squared (MRS) method, which can cover both seasonal and diurnal scales, for Eabs quantification. Using field measurement data in Guangzhou, the aims of this study are to explore (1)?the temporal dynamics of BC optical properties at seasonal (wet season, 31?July–10?September; dry season, 15?November?2017–15?January?2018) and diel scales (1 h time resolution) in the typical urban environment and (2)?the influencing factors on Eabs temporal variability. Mass absorption efficiency at 520 nm by primary aerosols (MAEp520) determined by the MRS method exhibited a strong seasonality (8.6 m2 g?1 in the wet season and 16.8 m2 g?1 in the dry season). Eabs520 was higher in the wet season (1.51±0.50) and lower in the dry season (1.29±0.28). Absorption ?ngstr?m exponent (AAE470–660) in the dry season (1.46±0.12) was higher than that in the wet season (1.37±0.10). Collective evidence showed that the active biomass burning (BB) in the dry season effectively altered the optical properties of BC, leading to elevated MAE, MAEp and AAE in the dry season compared to those in the wet season. Diurnal Eabs520 was positively correlated with AAE470–660 (R2=0.71) and negatively correlated with the AE33 aerosol loading compensation parameter (k) (R2=0.74) in the wet season, but these correlations were significantly weaker in the dry season, which may be related to the impact of BB. This result suggests that during the wet season, the lensing effect was more likely dominating the AAE diurnal variability rather than the contribution from brown carbon (BrC). Secondary processing can affect Eabs diurnal dynamics. The Eabs520 exhibited a clear dependency on the ratio of secondary organic carbon to organic carbon (SOC∕OC), confirming the contribution of secondary organic aerosols to Eabs; Eabs520 correlated well with nitrate and showed a clear dependence on temperature. This new finding implies that gas–particle partitioning of semivolatile compounds may potentially play an important role in steering the diurnal fluctuation of Eabs520. In the dry season, the diurnal variability in Eabs520 was associated with photochemical aging as evidenced by the good correlation (R2=0.69) between oxidant concentrations (Ox=O3+NO2) and Eabs520.
机译：黑碳（BC）气溶胶已被广泛认为是大气中的重要气候。在大气老化期间BC涂层可能发生光吸收的扩增，这是在获得BC的辐射强制方面仍然不确定的效果。对吸收增强因子（EAB）的现有研究对季节性和昼夜鳞片的覆盖率差。在这项研究中，我们应用了最近开发的最小R平方（MRS）方法，该方法可以涵盖季节性和昼夜尺度，用于EABS量化。使用广州的现场测量数据，这项研究的目的是探索（1）？季节性（湿季，31岁）的BC光学性质的时间动态（31〜10？9月;旱季，15？11月15日？2017-15 ？2018年1月？2018年）和DIEL尺度（DIEL SCALES（1 H时间分辨率）在典型的城市环境中和（2）？对EABS时间变异性的影响因素。由MRS方法测定的原发性气溶胶（MAP520）为520nm的质量吸收效率表现出强烈的季节性（湿季节8.6m 2 g？1，干燥季节中的16.8m 2 g？1）。湿季节（1.51±0.50）eabs520较高，干燥季节较低（1.29±0.28）。在干燥季节（1.46±0.12）的湿季节（1.46±0.12）的吸收？Ngstr？M代表（AAE470-660）高于湿季节（1.37±0.10）。集体证据表明，干燥季节中的活性生物质燃烧（BB）有效改变了BC的光学性质，与湿季节相比，干燥季节的Mae，Maep和Aae升高。昼夜EABS520与AAE470-660（R2 = 0.71）呈正相关，并在湿季与AE33气溶胶加载补偿参数（K）（R2 = 0.74）负相关，但干燥季节中这些相关性较弱，可能与BB的影响有关。该结果表明，在潮湿的季节期间，镜片效果更可能占据AAE昼夜变异性而不是棕色碳（BRC）的贡献。二次处理可以影响EABS昼夜动态。 EABS520表现出明显依赖于二次有机碳与有机碳（SoC / OC）的比率，证实二次有机气溶胶对EAB的贡献; EABS520用硝酸盐相关，并显示出明显的温度依赖。这种新发现意味着半溶血化合物的气体颗粒分配可能在转向EABS520的昼夜波动方面可能发挥重要作用。在干燥的季节中，EABS520中的昼夜变异性与光化学老化有关，如氧化剂浓度（OX = O3 + NO2）和EABS520之间的良好相关性（R2 = 0.69）所证明。

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