Model for acid-base chemistry in nanoparticle growth (MABNAG)
Model for acid-base chemistry in nanoparticle growth (MABNAG)
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DOI：
10.5194/acp-13-12507-2013
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发表时间：
2013-12
影响因子：
6.3
通讯作者：
T. Yli-Juuti;K. Barsanti;L. H. Ruiz;A. Kieloaho;U. Makkonen;T. Petäjä;T. Ruuskanen;M. Kulmala
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文献类型：
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作者：
T. Yli-Juuti;K. Barsanti;L. H. Ruiz;A. Kieloaho;U. Makkonen;T. Petäjä;T. Ruuskanen;M. Kulmala
新形成的大气次级气溶胶粒子的气候效应在很大程度上取决于它们的凝结增长率。然而，所有的蒸气冷凝在大气纳米颗粒上并使其生长到气候相关的尺寸还没有被确定，并且颗粒相过程对颗粒生长速率的影响知之甚少。除了硫酸之外，已知有机化合物对大气纳米颗粒生长有显著贡献。在这项研究中，一个粒子生长模型MABNAG（模型的酸碱化学在纳米粒子生长），研究盐的形成对纳米粒子生长的影响，这已被提出作为一个潜在的机制，降低平衡蒸气压的有机化合物通过在颗粒相的解离，从而防止其蒸发。MABNAG是一个单分散水相颗粒模型，它将凝聚动力学与颗粒相化学耦合起来。考虑了非零等容蒸汽压的冷凝，包括尺寸和成分依赖性。该模型被应用于大气相关系统与硫酸，一种有机酸，氨，一种胺和水在气相中允许冷凝在3-20 nm的颗粒。解离的有机酸的效果被发现是小的典型的北方森林网站的环境条件下，但相当大的碱丰富的环境（气相浓度约10 - 10厘米3的总和的碱）。碱对颗粒质量的贡献随颗粒尺寸的增大而减小，但在非常高的碱气相浓度下除外。胺相对于氨的相对重要性作为颗粒尺寸的函数没有显著变化。虽然我们的研究结果给出了合理的初步估计的最大贡献的盐的形成纳米颗粒的生长，进一步的研究，例如，大气有机物的热力学性质，低挥发性有机物和胺的浓度，沿着的研究调查热力学的applicability为最小的纳米颗粒需要真正理解的酸碱化学大气纳米颗粒。
Climatic effects of newly-formed atmospheric sec- ondary aerosol particles are to a large extent determined by their condensational growth rates. However, all the vapours condensing on atmospheric nanoparticles and growing them to climatically relevant sizes are not identified yet and the ef- fects of particle phase processes on particle growth rates are poorly known. Besides sulfuric acid, organic compounds are known to contribute significantly to atmospheric nanoparti- cle growth. In this study a particle growth model MABNAG (Model for Acid-Base chemistry in NAnoparticle Growth) was developed to study the effect of salt formation on nanoparticle growth, which has been proposed as a poten- tial mechanism lowering the equilibrium vapour pressures of organic compounds through dissociation in the particle phase and thus preventing their evaporation. MABNAG is a model for monodisperse aqueous particles and it couples dynamics of condensation to particle phase chemistry. Non-zero equi- librium vapour pressures, with both size and composition de- pendence, are considered for condensation. The model was applied for atmospherically relevant systems with sulfuric acid, one organic acid, ammonia, one amine and water in the gas phase allowed to condense on 3-20 nm particles. The ef- fect of dissociation of the organic acid was found to be small under ambient conditions typical for a boreal forest site, but considerable for base-rich environments (gas phase concen- trations of about 10 10 cm 3 for the sum of the bases). The contribution of the bases to particle mass decreased as parti- cle size increased, except at very high gas phase concentra- tions of the bases. The relative importance of amine versus ammonia did not change significantly as a function of parti- cle size. While our results give a reasonable first estimate on the maximum contribution of salt formation to nanoparticle growth, further studies on, e.g. the thermodynamic properties of the atmospheric organics, concentrations of low-volatility organics and amines, along with studies investigating the ap- plicability of thermodynamics for the smallest nanoparticles are needed to truly understand the acid-base chemistry of at- mospheric nanoparticles.