Lability of secondary organic particulate matter
Lability of secondary organic particulate matter
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DOI：
10.1073/pnas.1603138113
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发表时间：
2016-11-08
影响因子：
11.1
通讯作者：
Martin, Scot T.
中科院分区：
文献类型：
--
作者：
Liu, Pengfei;Li, Yong Jie;Martin, Scot T.
地球自然气候系统和人工气候系统中的能量流动受到大气颗粒物（PM）浓度的强烈影响。对于浓度的预测，半挥发性有机化合物（SVOC）之间的有机PM和周围的蒸汽的平衡分配已被广泛假设，但最近的观察表明，有机PM可以是半固体或固体的某些大气条件下，可能表明SVOC的吸收和释放可以足够慢，平衡不占上风的时间尺度相关的大气过程。在此，在一系列的实验室实验中，代表类似的大气有机PM的二次有机材料的膜的质量不稳定性直接通过蒸发速率和蒸汽质量浓度的石英晶体微量天平测量确定。有很大的差异，电影代表的人为相比，生物源。对于代表人为PM的膜，蒸发速率和蒸汽质量浓度增加高于阈值相对湿度（RH）在20%和30%之间，表明快速分区以上的过渡RH，但不低于。低于阈值，平衡的特征时间估计为1周的典型大小的颗粒。相反，对于代表生物源PM的膜，没有观察到RH阈值，这表明所有RH都能迅速获得平衡分配。生物源情况下的有效扩散速率D-org至少是人为情况下的103倍。这些差异应占实验室数据的解释，以及在地球大气中的有机PM建模。
The energy flows in Earth's natural and modified climate systems are strongly influenced by the concentrations of atmospheric particulate matter (PM). For predictions of concentration, equilibrium partitioning of semivolatile organic compounds (SVOCs) between organic PM and the surrounding vapor has widely been assumed, yet recent observations show that organic PM can be semisolid or solid for some atmospheric conditions, possibly suggesting that SVOC uptake and release can be slow enough that equilibrium does not prevail on timescales relevant to atmospheric processes. Herein, in a series of laboratory experiments, the mass labilities of films of secondary organic material representative of similar atmospheric organic PM were directly determined by quartz crystal microbalance measurements of evaporation rates and vapor mass concentrations. There were strong differences between films representative of anthropogenic compared with biogenic sources. For films representing anthropogenic PM, evaporation rates and vapor mass concentrations increased above a threshold relative humidity (RH) between 20% and 30%, indicating rapid partitioning above a transition RH but not below. Below the threshold, the characteristic time for equilibration is estimated as up to 1 wk for a typically sized particle. In contrast, for films representing biogenic PM, no RH threshold was observed, suggesting equilibrium partitioning is rapidly obtained for all RHs. The effective diffusion rate D-org for the biogenic case is at least 103 times greater than that of the anthropogenic case. These differences should be accounted for in the interpretation of laboratory data as well as in modeling of organic PMin Earth's atmosphere.