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首页> 外文期刊>Atmospheric chemistry and physics >Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part 1: Treatment of inorganic electrolytes and organic compounds in the condensed phase
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Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part 1: Treatment of inorganic electrolytes and organic compounds in the condensed phase

机译：空气质量模型中不确定性对气溶胶成分热力学性质的影响-第1部分：冷凝相中无机电解质和有机化合物的处理

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Air quality models that generate the concentrations of semi-volatile andother condensable organic compounds using an explicit reaction mechanismrequire estimates of the physical and thermodynamic properties of thecompounds that affect gas/aerosol partitioning: vapour pressure (as asubcooled liquid), and activity coefficients in the aerosol phase. The modelof Griffin, Kleeman and co-workers (e.g., Griffin et al., 2003; Kleeman et al., 1999) assumes that aerosol particles consist of an aqueous phase,containing inorganic electrolytes and soluble organic compounds, and ahydrophobic phase containing mainly primary hydrocarbon material. Thirtyeight semi-volatile reaction products are grouped into ten surrogate specieswhich partition between the gas phase and both phases in the aerosol.Activity coefficients of the organic compounds are calculated using UNIFAC.In a companion paper (Clegg et al., 2008) we examine the likelyuncertainties in the vapour pressures of the semi-volatile compounds andtheir effects on partitioning over a range of atmospheric relativehumidities. In this work a simulation for the South Coast Air Basinsurrounding Los Angeles, using lower vapour pressures of the semi-volatilesurrogate compounds consistent with estimated uncertainties in the boilingpoints on which they are based, yields a doubling of the predicted 24-haverage secondary organic aerosol concentrations. The dependency of organiccompound partitioning on the treatment of inorganic electrolytes in the airquality model, and the performance of this component of the model, aredetermined by analysing the results of a trajectory calculation using anextended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications areidentified where substantial efficiency gains can be made, principally: theomission of dissociation of the organic acid surrogates; restriction ofaerosol organic compounds to one of the two phases (aqueous or hydrophobic)where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organiccompounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in theaqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobicphase) and are therefore almost invariant. The implications of the resultsfor the development of aerosol models are discussed.
机译：使用显式反应机制生成半挥发性和其他可冷凝有机化合物浓度的空气质量模型需要估算影响气体/气溶胶分配的化合物的物理和热力学性质：蒸气压（作为过冷液体）和气溶胶中的活度系数相。 Griffin，Kleeman及其同事的模型（例如，Griffin等，2003; Kleeman等，1999）假设气溶胶颗粒由水相组成，其包含无机电解质和可溶性有机化合物，而疏水相则主要包含初级碳氢化合物材料。 38种半挥发性反应产物被分为十种替代物，它们在气溶胶中在气相和气相之间分配，使用UNIFAC计算有机化合物的活度系数。在同行论文中（Clegg et al。，2008），我们研究了半挥发性化合物的蒸气压可能存在不确定性，以及它们在一定范围的大气相对湿度下对分配的影响。在这项工作中，围绕洛杉矶的南海岸空气盆地的模拟使用半挥发性替代化合物的较低蒸气压，以及与它们所基于的沸点的估计不确定性相一致的结果，得出的预测值是平均24倍的二次有机气溶胶浓度的两倍。通过使用气溶胶无机模型的扩展版本分析轨迹计算的结果，可以确定空气质量模型中有机化合物分配对无机电解质处理的依赖性以及该模型组件的性能。 Wexler and Clegg（2002）。确定了可以大幅度提高效率的简化方法，主要是：避免了有机酸替代物的离解;将气溶胶有机化合物限制在两相（水相或疏水相）之一中，其中平衡计算表明在任一方向上都有很强的分配作用;用于模拟的有机化合物活度系数的单一计算，其中它们是由任一相中存在高浓度的一种组分（即水相中的水或疏水相中的碳氢化合物替代化合物P8）确定的，因此几乎不变。讨论了结果对气溶胶模型开发的意义。

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