| 二次有机气溶胶壳对氯化钠核吸湿性的影响:基于单颗粒微观尺度 |
| 摘要点击 2347 全文点击 732 投稿时间：2019-08-29 修订日期：2019-12-01 |
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| 中文关键词 二次有机气溶胶 氯化钠 α-蒎烯 臭氧氧化 吸湿性 |
| 英文关键词 secondary organic aerosols NaCl α-pinene ozone oxidation hygroscopicity |
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| 中文摘要 |
| 大气颗粒物吸湿特性能够影响颗粒物的光学效应、云凝结核活性和颗粒物表面的非均相反应特性.目前关于颗粒物内混结构的研究较多，但针对二次有机物对无机盐吸湿性影响的研究还比较缺乏.本研究利用一个2 L的气相流动反应管，实验室模拟α-蒎烯臭氧氧化生成二次有机气溶胶过程，然后以氯化钠为种子气溶胶在流动反应管末端分别收集11、15和20 h这3组不同时长二次有机物包裹无机盐具有核-壳结构的单颗粒样品.透射电镜结果显示该模拟系统可以制备典型氯化钠核-有机物壳的颗粒，且有机物壳的厚度随着收集时长的延长变厚.单颗粒吸湿系统研究显示，有机物壳会影响氯化钠的潮解点（纯氯化钠潮解点为77%），并且会束缚氯化钠核的吸湿增长，表现如下：11 h收集时长下单颗粒样品中氯化钠核在相对湿度75.5%时开始潮解，并于78%时完全潮解，85%湿度下吸湿增长因子为2.5；15 h单颗粒样品中氯化钠核潮解范围为75%~78.5%，85%湿度下湿增长因子为2.3；20 h样品中核潮解范围则为76%~83%，85%湿度下湿增长因子为1.8.本研究结果表明：①二次有机物壳影响并使氯化钠提前吸湿潮解；②有机物壳滞后氯化钠的完全潮解点且有机壳越厚滞后作用越明显；③有机物壳抑制了氯化钠核的吸湿增长因子.该研究表明目前通过大气模式模拟及外场观测手段研究颗粒物吸湿性时应考虑无机盐颗粒表面二次有机包裹层的影响. |
| 英文摘要 |
| The hygroscopicity of atmospheric particulate matter can determine its optical behaviors, cloud condensation nuclei activity, and heterogeneous chemical reaction on the surface. However, the effect of secondary organic matter on the hygroscopicity of inorganic salts is still rarely studied. In this study, a 2 L gas-phase flow tube was used to stimulate the oxidation process of α-pinene. NaCl particles at the end of the flow tube served as seeds to absorb the product of α-pinene oxidation. The absorption times were 11, 15, and 20 h. Transmission electron microscopy results show that this system could produce particles with typical core-shell structure, and that the thickness of the organic shell would be thicker with longer collection time. Results from individual particle hygroscopic systems indicate that the organic shell can affect the deliquescent point of NaCl (pure NaCl deliquesces at 77%):for 11 h collection time, the NaCl core began to deliquesce at 75.5% relative humidity, and completely deliquesced at 78%; for 15 h collection time, the deliquescent range of the NaCl core was 75%-78.5%; and the deliquescent range was 76%-83% for the NaCl core with 20 h collection time. Furthermore, the organic shell could affect the hygroscopic growth of the NaCl core:the growth factor of the NaCl core with 11 h, 15 h, and 20 h collection time was 2.5, 2.3, and 1.8, respectively. These results indicate that:① the secondary organic shell could cause water absorption of the NaCl core in advance:② the organic shell could postpone the completely deliquescent point of the NaCl core, and this effect is more obvious with a thicker organic shell; ③ the organic shell could restrain the hygroscopic growth factor of the NaCl core. This study suggests that it is necessary to consider the influence of secondary organic matter on inorganic salts when studying the hygroscopic properties of atmospheric particles in climate models and field observations. |
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