A predictive model for salt nanoparticle formation using heterodimer stability calculations
A predictive model for salt nanoparticle formation using heterodimer stability calculations
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DOI：
10.5194/acp-21-11637-2021
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发表时间：
2021-08-05
影响因子：
6.3
通讯作者：
Myllys, Nanna
中科院分区：
文献类型：
--
作者：
Chee, Sabrina;Barsanti, Kelley;Myllys, Nanna
酸碱团簇和稳定的盐形成是大气中新粒子形成事件的关键驱动因素。在这项研究中，我们探讨了盐异二聚体（一酸一碱簇）的稳定性作为气相酸度、水相酸度、异二聚体质子转移、蒸气压、偶极矩和极化率的函数。发现气相酸度是异二聚体稳定性的最佳预测因子。然后，我们分析了在10(5)到10(9)分子cm 3的单体浓度和248到348K的温度范围内，硫酸盐的异二聚体稳定性与J（4x4）之间的关系，J（4x4）是理论预测的四酸四碱簇的形成速率，发现异二聚体的稳定性与J（4x4）形成对数正态关系。然而，温度和浓度的影响使得J（4x4）难以形成预测表达。为了减少这些影响，根据异源二聚体的稳定性计算了异源二聚体的浓度，并给出了一个表达式，可以预测任何盐的J(4x4)，给定酸和碱的单体浓度近似相等，以及单体浓度和温度的知识。通过与实验数据的比较，对该参数化方法在硫酸-氨体系中的预测精度进行了验证，精度在2个数量级以内。我们表明，通过定义一个我们称之为归一化异二聚体浓度Phi的新术语，可以创建一个简单的参数化，该参数化包含对温度和单体浓度对J（4x4）的依赖。对于弱硫酸盐（气相酸度差> 95 kcal mol(-1)）， J(4x4) vs. Phi的曲线坍塌为单一单调曲线，可用于在大气模型中精确估计2个数量级内的J（4x4）。
Acid-base clusters and stable salt formation are critical drivers of new particle formation events in the atmosphere. In this study, we explore salt heterodimer (a cluster of one acid and one base) stability as a function of gas-phase acidity, aqueous-phase acidity, heterodimer proton transference, vapor pressure, dipole moment and polarizability for salts comprised of sulfuric acid, methanesulfonic acid and nitric acid with nine bases. The best predictor of heterodimer stability was found to be gas-phase acidity. We then analyzed the relationship between heterodimer stability and J(4x4), the theoretically predicted formation rate of a four-acid, fourbase cluster, for sulfuric acid salts over a range of monomer concentrations from 10(5) to 10(9) molec cm 3 and temperatures from 248 to 348K and found that heterodimer stability forms a lognormal relationship with J(4x4). However, temperature and concentration effects made it difficult to form a predictive expression of J(4x4). In order to reduce those effects, heterodimer concentration was calculated from heterodimer stability and yielded an expression for predicting J(4x4) for any salt, given approximately equal acid and base monomer concentrations and knowledge of monomer concentration and temperature. This parameterization was tested for the sulfuric acid-ammonia system by comparing the predicted values to experimental data and was found to be accurate within 2 orders of magnitude. We show that one can create a simple parameterization that incorporates the dependence on temperature and monomer concentration on J(4x4) by defining a new term that we call the normalized heterodimer concentration, Phi. A plot of J(4x4) vs. Phi collapses to a single monotonic curve for weak sulfate salts (difference in gas-phase acidity > 95 kcal mol(-1)) and can be used to accurately estimate J(4x4) within 2 orders of magnitude in atmospheric models.