Laboratory Study on the Hygroscopic Behavior of External and Internal C2-C4 Dicarboxylic Acid-NaCl Mixtures
Laboratory Study on the Hygroscopic Behavior of External and Internal C2-C4 Dicarboxylic Acid-NaCl Mixtures
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DOI：
10.1021/es4023267
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发表时间：
2013-09-17
影响因子：
11.4
通讯作者：
He, Hong
中科院分区：
文献类型：
--
作者：
Ma, Qingxin;Ma, Jinzhu;He, Hong
在野外测量中，大气气溶胶通常是各种无机和有机成分的混合物，但这种混合状态对气溶胶颗粒吸湿性的影响尚不清楚。在这项研究中，研究了C-2-C-4二元酸和氯化钠的混合物的吸湿行为。对于内外混合的丙二酸-氯化钠和琥珀酸-氯化钠颗粒，水分含量与化学组成之间存在相关性，用Zdanovsldi-Stokes-Robinson(ZSR)方法可以很好地预测在相对湿度(RH)大于80%的情况下这些混合物的水分含量。相反，草酸-氯化钠混合物的总含水率与各化学成分的含水率之间存在非线性关系。与ZSR方法的预测值相比，草酸在外部混合物中的溶解导致总水分含量增加，而在内部混合物中形成吸湿性较小的草酸二钠导致总水分含量显著下降。此外，我们还发现，在加湿和除湿过程中，二元羧酸钠的吸湿性对决定二元酸-氯化钠混合物的水化学性质起着至关重要的作用。实验还发现，在外加草酸-氯化钠混合物中，草酸的水化和氯化钠的潮解没有改变。丙二醛和氯化钠在内外混合物中的潮解相对湿度(DRHs)均降低。这些结果有助于了解二元酸转化为二元酸盐的过程，以及大气中草酸盐取代氯的过程。结果表明，共存组分对混合气溶胶吸湿行为的影响不容忽视。
Atmospheric aerosol is usually found to be a mixture of various inorganic and organic components in field measurements, whereas the effect of this mixing state on the hygroscopicity of aerosol particles has remained unknown. In this study, the hygroscopic behavior of mixtures of C-2-C-4 dicarboxylic adds and NaCl was investigated. For both externally and internally mixed malonic acid-NaCl and succinic acid-NaCl particles, correlation between water content and chemical composition was observed and the water content of these mixtures at relative humidity (RH) above 80% can be well predicted by the Zdanovsldi-Stokes-Robinson (ZSR) method. In contrast, a nonlinear relation between the total water content of the mixtures and the water content of each chemical composition separately was found for oxalic acid-NaCl mixtures. Compared to the values predicted by the ZSR method, the dissolution of oxalic acid in external mixtures resulted in an increase in the total water content, whereas the formation of less hygroscopic disodium oxalate in internal mixtures led to a significant decrease in the total water content. Furthermore, we found that the hygroscopicity of the sodium dicarboxylate plays a critical role in determining the aqueous chemistry of dicarboxylic acid-NaCl mixtures during the humidifying and dehumidifying process. It was also found that the hydration of oxalic acid and the deliquescence of NaCl did not change in external oxalic acid-NaCl mixtures. The deliquescence relative humidity (DRHs) for both malonic add and NaCl decreased in both external and internal mixtures. These results could help in understanding the conversion processes of dicarboxylic acids to dicarboxylate salts, as well as the substitution of Cl by oxalate in the atmosphere. It was demonstrated that the effect of coexisting components on the hygroscopic behavior of mixed aerosols should not be neglected.