Widening the gap between measurement and modelling of secondary organic aerosol properties?
Widening the gap between measurement and modelling of secondary organic aerosol properties?
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DOI：
10.5194/acp-10-2577-2010
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发表时间：
2010-01-01
影响因子：
6.3
通讯作者：
McFiggans, G.
中科院分区：
文献类型：
--
作者：
Good, N.;Topping, D. O.;McFiggans, G.
使用两种不同复杂性的模型研究了在存在或不存在硫酸铵种子气溶胶的情况下，由α-蒎烯的室光氧化产生的二次有机气溶胶颗粒的测得的亚饱和吸湿性和云活化潜力之间的联系。一个简单的单吸湿性参数模型和一个更复杂的模型（包括表面效应）被用来评估所需的细节，以预测云凝结核（CCN）的活动从亚饱和水吸收。通过三个吸湿性串联微分迁移率分析仪（HTDMA）仪器测量的亚饱和吸水率用于确定模型中使用的水活度。预测的云凝结核活性与使用连续流云凝结核计数器测量的云凝结核活化电位进行比较。使用更复杂的模型公式与测量的云活化进行调和，可以实现增长液滴的广泛不同的假设表面张力行为;这完全由用作水活性数据源的仪器确定。这种不可靠的推导的水活度作为溶质浓度的函数，从次饱和吸湿性数据表明，在使用这些数据预测云凝结核的行为与一个显着的有机部分的颗粒的限制。同样，更简单的单参数模型预测云激活行为的能力取决于用于测量亚饱和吸湿性的仪器和用于提供模型输入的相对湿度。然而，协议观察到无机盐溶液颗粒，这是由所有仪器测量与理论一致。HTDMA数据的差异，从验证和广泛使用的仪器意味着，它不能肯定地说，所需的细节来预测CCN活性从亚饱和吸湿性。为了缩小吸湿增长和云凝结核活动测量之间的差距，必须了解所涉及的过程，并广泛保证仪器的质量。由于HTDMA数据的差异，无法从此处给出的结果中判断是否发生：i）表面张力抑制; ii）体相到表面的分配很重要; iii）水活度系数随溶质浓度的变化而显著变化。
The link between measured sub-saturated hygroscopicity and cloud activation potential of secondary organic aerosol particles produced by the chamber photo-oxidation of alpha-pinene in the presence or absence of ammonium sulphate seed aerosol was investigated using two models of varying complexity. A simple single hygroscopicity parameter model and a more complex model (incorporating surface effects) were used to assess the detail required to predict the cloud condensation nucleus (CCN) activity from the sub-saturated water uptake. Sub-saturated water uptake measured by three hygroscopicity tandem differential mobility analyser (HTDMA) instruments was used to determine the water activity for use in the models. The predicted CCN activity was compared to the measured CCN activation potential using a continuous flow CCN counter.Reconciliation using the more complex model formulation with measured cloud activation could be achieved widely different assumed surface tension behavior of the growing droplet; this was entirely determined by the instrument used as the source of water activity data. This unreliable derivation of the water activity as a function of solute concentration from sub-saturated hygroscopicity data indicates a limitation in the use of such data in predicting cloud condensation nucleus behavior of particles with a significant organic fraction. Similarly, the ability of the simpler single parameter model to predict cloud activation behaviour was dependent on the instrument used to measure sub-saturated hygroscopicity and the relative humidity used to provide the model input. However, agreement was observed for inorganic salt solution particles, which were measured by all instruments in agreement with theory.The difference in HTDMA data from validated and extensively used instruments means that it cannot be stated with certainty the detail required to predict the CCN activity from sub-saturated hygroscopicity. In order to narrow the gap between measurements of hygroscopic growth and CCN activity the processes involved must be understood and the instrumentation extensively quality assured. It is impossible to say from the results presented here due to the differences in HTDMA data whether: i) Surface tension suppression occurs ii) Bulk to surface partitioning is important iii) The water activity coefficient changes significantly as a function of the solute concentration.