Shang Yue, Yu Huan, Mao Yu-Hao, Wang Cheng, Xie Ming-Jie
Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science & Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China.
Department of Atmospheric Sciences, School of Environmental Studies, China University of Geosciences, Wuhan 430074, China.
Huan Jing Ke Xue. 2021 Mar 8;42(3):1228-1235. doi: 10.13227/j.hjkx.202006219.
The light absorption of organic components in PM was investigated at a suburban site in northern Nanjing from September 2018 to September 2019, and PM compositional data and principal component analysis (PCA) were used to identify the sources of light-absorbing organic carbon (brown carbon, BrC). The results showed that the average light absorption coefficients of water-soluble organic carbon (WSOC) and methanol extractable organic carbon (MEOC) were (3.22±2.18) Mm (Abs) and (7.69±4.93) Mm(Abs), respectively. Significant correlations were observed between Abs and mass concentrations of WSOC (=0.72, <0.01) and between Abs and mass concentrations of MEOC (=0.62, =0.04). Both Abs and Abs exhibited seasonal variations, with higher values during winter than during summer,and higher diel variations at night than during the day. This can be attributed to meteorological characteristics during the winter and nighttime, i.e., decreased boundary layer height and increased atmospheric stability, enhanced primary emissions in winter,and stronger photobleaching effects during the summer and during the day. The annual average Abs/Abs ratio (2.60±0.92) was much larger than the average mass ratio of MEOC/WSOC (1.37±0.30), indicating that the water-insoluble fraction of MEOC had a stronger light absorption effect and dominated BrC absorption. No strong correlation (<0.60) was observed between WSOC, MEOC, Abs, and mass concentrations of K, indication that biomass burning was not the main source of BrC in the study location. The mass absorption efficiency of WSOC (MAE) and MEOC (MAE) and their ratios (MAE/MAE) showed similar seasonal variations to Abs. The average MAE value of the water-insoluble fraction of MEOC (4.10±5.15) m·g was 6.0 and 2.9 times higher than that of MAE and MAE, respectively, suggested that BrC absorption was primarily attributable to water-insoluble components. In comparison to the absorption Ångström exponent of WSOC (), displayed marked temporal variability, which might be related to the seasonal variation in the emission of water-insoluble chromophores. According to the PCA results, the light absorption of PM organic was mainly attributed to secondary formation and anthropogenic primary emissions rather than biomass burning.
2018年9月至2019年9月期间，在南京北郊的一个郊区站点对细颗粒物（PM）中有机成分的光吸收进行了研究，并利用PM成分数据和主成分分析（PCA）来确定吸光有机碳（棕碳，BrC）的来源。结果表明，水溶性有机碳（WSOC）和甲醇可萃取有机碳（MEOC）的平均光吸收系数分别为（3.22±2.18）Mm（Abs）和（7.69±4.93）Mm（Abs）。在Abs与WSOC质量浓度之间（=0.72，<0.01）以及Abs与MEOC质量浓度之间（=0.62，=0.04）观察到显著相关性。Abs和Abs均呈现季节性变化，冬季的值高于夏季，夜间的日变化高于白天。这可归因于冬季和夜间的气象特征，即边界层高度降低和大气稳定性增加，冬季一次排放增强，以及夏季和白天更强的光漂白效应。年平均Abs/Abs比值（2.60±0.92）远大于MEOC/WSOC的平均质量比（1.37±0.30），表明MEOC的水不溶性部分具有更强的光吸收效应并主导了BrC吸收。在WSOC、MEOC、Abs与K的质量浓度之间未观察到强相关性（<0.60），这表明生物质燃烧不是研究地点BrC的主要来源。WSOC（MAE）和MEOC（MAE）的质量吸收效率及其比值（MAE/MAE）与Abs呈现相似的季节性变化。MEOC水不溶性部分的平均MAE值（4.10±5.15）m·g分别比MAE和MAE高6.0倍和2.9倍，这表明BrC吸收主要归因于水不溶性成分。与WSOC的吸收埃指数（）相比，呈现出明显的时间变异性，这可能与水不溶性发色团排放的季节性变化有关。根据PCA结果，PM有机成分的光吸收主要归因于二次形成和人为一次排放，而非生物质燃烧。
