Differing effects of escalating pollution on absorption and scattering efficiencies of aerosols: Toward co-beneficial air quality enhancement and climate protection measures
Differing effects of escalating pollution on absorption and scattering efficiencies of aerosols: Toward co-beneficial air quality enhancement and climate protection measures
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DOI：
10.1016/j.atmosenv.2020.117570
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发表时间：
2020-07
影响因子：
5
通讯作者：
Yuzhe Zhang;Guorui Zhi;Wenjing Jin;Lei Wang;Sicong Guo;Rong Shi;Jianzhong Sun;M. Cheng;
中科院分区：
文献类型：
--
作者：
Yuzhe Zhang;Guorui Zhi;Wenjing Jin;Lei Wang;Sicong Guo;Rong Shi;Jianzhong Sun;M. Cheng;
气溶胶的质量吸收效率（MAE）和质量散射效率（MSE）是决定其消光能力的关键。在北方冬季，由于气溶胶的一次排放和二次生成量高，加上天气条件的变化，空气晴朗和灰霾天气交替出现。这些事件有助于详细调查污染水平的显著变化如何影响MAE和MSE，它们还可以确定当前的空气质量改善措施是否也有利于缓解气候变化，以避免清洁空气的气候副作用。在本研究中，2016-2017年冬季在中国北京进行了为期一个月的观察活动。利用光声散射仪对大气气溶胶在870 nm红外波段的吸收系数（σ a）和散射系数（σ s）进行了现场测量。MAE和MSE随污染水平的增加而变化。当PM 2.5< 100 μg m− 3时，MAE与PM 2.5浓度呈正相关，当PM 2.5= 100-200 μg m − 3时，MAE的增加有所下降，随后MAE趋于稳定。与此相反，MSE随着PM 2.5的增加而持续增加。气溶胶的单次散射强度（SSA）是σ a和σ s的函数，从0.827±0.018增加到0.827±0.018（平均值±标准偏差），对于底部颗粒物浓度组为（0，25] μg m-3，对于顶部颗粒物浓度组为（300，400] μg m-3，0.924±0.007），这表明SSA和PM 2.5之间存在正相关关系。这些观测结果表明，目前的清洁空气措施有可能削弱或消除北方环境气溶胶的冷却作用。似乎没有以前的研究涉及在相同波长下同时采集σ a和σ s，以确定空气污染的增加如何不同地影响MAE和MSE。可用于降低黑碳与PM 2.5比率的实际措施包括逐步淘汰或减少富含黑碳的来源，并推广降低黑碳与有机碳比率的技术。
The mass absorption efficiency (MAE) and mass scattering efficiency (MSE) of aerosols are critical to their light extinction capacity. In winter in northern China, episodes of clear air and heavy haze alternately occur due to the high primary emission and secondary formation of aerosols, coupled with changing weather conditions. These occurrences facilitate detailed investigation of how significant changes in the pollution level impact the MAE and MSE, they also enable the determination of whether current air quality improvement measures are also beneficial to the mitigation of climate change, to avoid climatic side effects of attempts to clean the air. In the present study, a one-month observation campaign was conducted in Beijing, China, during the 2016–2017 winter season. A photoacoustic extinctiometer, which is an in situ measurement instrument, was used to investigate the aerosol absorption coefficient (σ a) and scattering coefficient (σ s) at an infra-red wavelength of 870 nm. The MAE and MSE were found to vary differently with increasing pollution level. A positive correlation between the particulate matter concentration (PM 2.5) and the MAE was observed for PM 2.5< 100 μg m− 3, with the increase in the MAE declining for PM 2.5= 100–200 μg m− 3, and the MAE subsequently stabilizing. In contrast, the MSE continuously increased with increasing PM 2.5. The single scattering albedo (SSA), which governs the climatic effect of aerosols, was observed to be a function of both σ a and σ s, increasing from 0.827±0.018 (average±standard deviation) for a bottom particulate matter concentration group of (0, 25] μg m− 3 to 0.924±0.007 for a top particulate matter concentration group of (300, 400] μg m− 3, indicating a positive correlation between the SSA and PM 2.5. These observations suggest a risk of current clean air measures weakening or eliminating the cooling effect of ambient aerosols in northern China. It seems that no previous study has involved the simultaneous acquisition of σ a and σ s at the same wavelength with the purpose of determining how increasing air pollution differently impacts the MAE and MSE. Practical measures that can be used to decrease the black carbon-to-PM 2.5 ratio include phasing out or reducing black carbon-rich sources and promoting technologies that decrease the black carbon-to-organic carbon ratio.