Gas–particle partitioning of polyol tracers at a suburban site in Nanjing, east China: increased partitioning to the particle phase
Gas–particle partitioning of polyol tracers at a suburban site in Nanjing, east China: increased partitioning to the particle phase
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DOI：
10.5194/acp-21-12141-2021
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发表时间：
2021-08
影响因子：
6.3
通讯作者：
Chao Qin;Y. Gou;Yuhang Wang;Y. Mao;H. Liao;Qin'geng Wang;M. Xie
中科院分区：
文献类型：
--
作者：
Chao Qin;Y. Gou;Yuhang Wang;Y. Mao;H. Liao;Qin'geng Wang;M. Xie
抽象的。水溶性有机化合物的气体-颗粒分配在影响大气中有机气溶胶的形成、传输和寿命方面发挥着重要作用，但其特征却很少。在这项工作中，在中国东部长江三角洲西部的郊区同时测量了异戊二烯氧化产物（C5-烯烃三醇和2-甲基三醇）、左旋葡聚糖和糖醇的气相和颗粒相浓度。所有目标多元醇主要分布在颗粒相中 (85.9%–99.8%)。鉴于测量和蒸气压预测的不确定性，无法确定颗粒相分数对蒸气压的依赖性。为了探索气溶胶液态水对多元醇示踪剂的气体-颗粒分配的影响，基于气溶胶中气体与有机相和水相的平衡，提出了三种分配方案（案例1-3）。如果假定颗粒有机物 (OM) 为唯一的吸收相（情况 1），则异戊二烯氧化产物和左旋葡聚糖的基于测量的吸收分配系数 (Kp,OMm) 比预测值 (Kp,OMt) 大 10 倍以上。当包括在单独水相中的溶解度时，只要水溶性和水不溶性 OM 分配到单独的（案例 2）或单一（案例 3）液相中，Kp,OMm 和 Kp,OMt 之间的一致性就会大大提高，这表明多元醇示踪剂在气溶胶中分配到水相中的情况不应被忽视。多元醇示踪剂基于测量的有效亨利定律系数 (KH,em) 比纯水中的预测值 (KH,wt) 高几个数量级。由于 log(KH,em/KH,wt) 与硫酸根离子摩尔浓度之间存在中等相关性，多元醇示踪剂的 KH,em 与 KH,wt 之间的差距无法通过定义“盐溶”效应的方程完全参数化，可能归因于反应吸收、水相反应、“类溶”原理等机制。这些研究结果也部分揭示了 有机气溶胶的观察和建模之间的差异。
Abstract. Gas–particle partitioning of water-soluble organic compounds plays a significant role in influencing the formation, transport, and lifetime of organic aerosols in the atmosphere, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9 %–99.8 %). Given the uncertainties in measurements and vapor pressure predictions, a dependence of particle-phase fractions on vapor pressures cannot be determined. To explore the impact of aerosol liquid water on gas–particle partitioning of polyol tracers, three partitioning schemes (Cases 1–3) were proposed based on equilibriums of gas vs. organic and aqueous phases in aerosols. If particulate organic matter (OM) is presumed as the only absorbing phase (Case 1), the measurement-based absorptive partitioning coefficients (Kp,OMm) of isoprene oxidation products and levoglucosan were more than 10 times greater than predicted values (Kp,OMt). The agreement between Kp,OMm and Kp,OMt was substantially improved when solubility in a separate aqueous phase was included, whenever water-soluble and water-insoluble OM partitioned into separate (Case 2) or single (Case 3) liquid phases, suggesting that the partitioning of polyol tracers into the aqueous phase in aerosols should not be ignored. The measurement-based effective Henry's law coefficients (KH,em) of polyol tracers were orders of magnitude higher than their predicted values in pure water (KH,wt). Due to the moderate correlations between log(KH,em/KH,wt) and molality of sulfate ions, the gap between KH,em and KH,wt of polyol tracers could not be fully parameterized by the equation defining “salting-in” effects and might be ascribed to mechanisms of reactive uptake, aqueous phase reaction, “like-dissolves-like” principle, etc. These study results also partly reveal the discrepancy between observation and modeling of organic aerosols.