The formation of terpene secondary organic aerosol (SOA) was simulated using the unified partitioning aerosol phase reaction model that predicted multiphase reactions of hydrocarbons in the presence of electrolytic inorganic aerosols. To predict oxygenated products from the atmospheric oxidation of terpenes, the master chemistry mechanism, an explicit gas kinetic mechanism, was implemented. The resulting products were then classified into 51 lumping groups using mass-based stoichiometric coefficients according to their volatility and aerosol phase reactivity. In the presence of wet inorganic aerosol, the SOA model was approached by liquid–liquid phase separation between the organic and inorganic phases due to the hydrophobicity of terpene products (oxygen to carbon ratios <0.6). The model streamlined three SOA formation pathways including partitioning of gaseous oxidized products onto both the organic aerosol and aqueous aerosol phases, oligomerization in the organic phase, and aqueous phase reactions (acid-catalyzed oligomerization and organosulfate formation). In the model, the peroxy radical autoxidation mechanism, which is a recently derived explicit mechanism to form highly oxygenated molecules, was also included to form less volatile products. The model simulation was demonstrated for SOA data that were produced through the photo-oxidation of three different monoterpenes (α-pinene, β-pinene, and d-limonene) under various experimental conditions in a large outdoor photochemical smog chamber. Terpene SOA growth was considerably accelerated in the aqueous phase anchored in acidic seeds but much weaker with neutral seeds. This tendency is quite different from that of isoprene SOA, which noticeably grows even in the neutral aqueous phase. Unlike hydrophilic isoprene products, terpene products are hydrophobic and weakly soluble in the aqueous phase, and thus, the neutral aqueous phase is insufficient to increase SOA mass. The model underestimated the production of polar functional groups, such as −OH, −COOH, and −ONO₂, compared to the compositions measured using Fourier-transform infrared spectral data. In particular, the model underestimated carboxylic acids due to the knowledge gaps in the mechanisms to form carboxylic acid in both gas-phase oxidation and in-particle chemistry. Under the current emission trends in which SO₂ and NO_x have been decreasing, the model simulation suggested that the reduction of sulfate is more efficient to reduce SOA mass than the reduction of NO_x.

中文翻译：

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使用显式机制模拟多相反应形成单萜 SOA

使用统一分配气溶胶相反应模型模拟萜烯二次有机气溶胶 (SOA) 的形成，该模型预测了在电解无机气溶胶存在下碳氢化合物的多相反应。为了预测萜烯在大气中氧化的氧化产物，实施了主化学机制，即一种明确的气体动力学机制。然后根据其挥发性和气溶胶相反应性，使用基于质量的化学计量系数将所得产品分为 51 个集总组。在存在湿无机气溶胶的情况下，由于萜烯产品的疏水性（氧碳比 <0.6），通过有机相和无机相之间的液-液相分离来接近 SOA 模型。该模型简化了三种 SOA 形成途径，包括将气态氧化产物分配到有机气溶胶和水气溶胶相、有机相中的低聚反应和水相反应（酸催化低聚反应和有机硫酸盐形成）。在该模型中，还包括过氧自由基自动氧化机制，这是最近推导出的形成高度氧化分子的明确机制，也被包括以形成挥发性较低的产品。SOA 数据通过三种不同的单萜（α-蒎烯、β-蒎烯和 在该模型中，还包括过氧自由基自动氧化机制，这是最近推导出的形成高度氧化分子的明确机制，也被包括以形成挥发性较低的产品。SOA 数据通过三种不同的单萜（α-蒎烯、β-蒎烯和 在该模型中，还包括过氧自由基自动氧化机制，这是最近推导出的形成高度氧化分子的明确机制，也被包括以形成挥发性较低的产品。SOA 数据通过三种不同的单萜（α-蒎烯、β-蒎烯和d-柠檬烯）在大型室外光化学烟雾室中的各种实验条件下。在固定在酸性种子中的水相中，萜烯 SOA 的生长显着加速，但在中性种子中要弱得多。这种趋势与异戊二烯 SOA 的趋势完全不同，异戊二烯 SOA 即使在中性水相中也明显增长。与亲水性异戊二烯产品不同，萜烯产品在水相中具有疏水性和微溶性，因此中性水相不足以增加 SOA 质量。该模型低估了极性官能团的产生，例如 -OH、-COOH 和 -ONO ₂，与使用傅立叶变换红外光谱数据测量的组合物相比。特别是，由于在气相氧化和粒子内化学中形成羧酸的机制方面存在知识空白，该模型低估了羧酸。在当前SO ₂和NO _x减少的排放趋势下，模型模拟表明硫酸盐的还原比NO _x的还原更有效地减少SOA质量。