广州城区黑碳气溶胶吸光增强特性研究

本研究运用最小相关系数法（MRS），使用元素碳（EC）作为示踪物，得到一次排放的质量吸光效率（MAE_p），结合黑碳仪（AE33）和有机碳/元素碳分析仪获得实测的质量吸光效率MAE_t，进而通过MAE_t/MAE_p的比值得出吸光增强系数（E_abs）.采样站点位于广州市城区暨南大学大气超级监测站，采样时间涵盖了干季（2019年1月26日~3月31日）和湿季（2018年5月1日~7月31日）.对广州市城区的黑碳气溶胶及其光学特征进行分析，EC在干季的平均浓度（1.93±1.38）μgC/m³高于湿季（1.46±0.75）μgC/m³，而E_abs520在干季的均值（1.26±0.34）低于湿季（1.63±0.55）.E_abs520在干湿季的日变化差异明显，但有机碳（OC）、EC、OC/EC、波长指数（AAE_470-660）均为干季高于湿季.分析发现气溶胶负载补偿参数k值与E_abs520在湿季呈现出较好的相关性，而在干季相关性较差，可能与生物质燃烧的影响有关；探讨了O₃、NO₂和SOC/OC对E_abs520的影响，在干季O₃与E_abs520的相关性较差（R²=0.21），在湿季较好（R²=0.46），SOC/OC却展现出了相反的关系，而NO₂在干季和湿季与E_abs520的相关性都较差（R²=0.01），并发现温度对E_abs520存在一定的影响.通过后向轨迹聚类分析发现，长距离传输气团的的黑碳E_abs520值较高.

The light absorption enhancement characteristics of black carbon aerosols in urban Guangzhou

In this study, Minimum R squared method (MRS), was used to calculate the primary mass absorption efficiency of the primary emissions (MAE_p) using elemental carbon (EC) as the tracer. The mass absorption efficiency of the ambient aerosols (MAE_t) was determined by co-located measurements of an Aethalometer and a carbon analyzer. The absorption enhancement factor at wavelength 520nm, E_abs520, was determined by the ratio of MAE_p/MAE_t. The sampling site was located at Jinan University Supersite. The sampling period covered both dry season (January 26~March 31, 2019) and wet season (May 1~July 31, 2018). The optical properties of BC were characterized in the urban area. The average EC concentration in the dry season was (1.93±1.38) μgC/m³, which was significantly higher than that in the wet season (1.46±0.75) μgC/m³. E_abs520 in the dry season (1.26±0.34) was lower than that in the wet season (1.63 ±0.55). The diurnal variations of E_abs520 behaved differently in the dry and wet seasons. OC, EC, OC/EC, and AAE_470-660 were higher in the dry season than in the wet season. The aerosol loading compensation parameter k and AAE_470-660 correlated well with E_abs520 on the diurnal scale in the wet season. No correlation was observed in the dry season, which might be related to the impact of biomass burning. The effects of O₃, NO₂ and SOC/OC on E_abs520 were discussed. The correlation between O₃ and E_abs520 was poor in the dry season (R²=0.21), and stronger in the wet season (R²=0.46), but SOC/OC showed the opposite relationship with E_abs520. Poor correlation between NO₂ and E_abs520 was observed in both wet and dry season (R²=0.01). Temperature dependence was observed on E_abs520 to a certain degree. The back-trajectory cluster analysis revealed that long-range transport air masses exhibited high E_abs520 values.