Modeling secondary organic aerosol using a dynamic partitioning approach incorporating particle aqueous-phase chemistry
Modeling secondary organic aerosol using a dynamic partitioning approach incorporating particle aqueous-phase chemistry
复制标题
使用结合颗粒水相化学的动态分配方法模拟二次有机气溶胶
DOI：
10.1016/j.atmosenv.2010.11.027
复制
发表时间：
2011
影响因子：
5
通讯作者：
R. Kamens
中科院分区：
文献类型：
--
作者：
H. Parikh;A. Carlton;W. Vizuete;R. Kamens
目前的空气质量模式(AQM)系统使用奥德姆型两产品或挥发性基组(VBS)方法来预测甲苯氧化形成的二次有机气溶胶(SOA)。对于AQM系统中的SOA模块，这两种方法中使用的化学计量系数和分配系数通常是在有限的一组条件下(例如，低湿度和初始(NH4)2SO4种子)在单室中进行的实验室研究得出的，并隐含着瞬时热力学平衡的假设。在这项研究中，我们评估了独立的甲苯实验室研究，其中包括初始甲苯、NOx、不形成SOA的碳氢化合物混合物、初始种子类型和湿度的不同组合实验。当根据这一观测数据集进行评估时，无论种子类型如何，在干燥条件下、在碳氢化合物混合物存在的情况下以及初始种子质量较低的情况下，奥德姆型和VBS方法都无法预测观察到的SOA。对于湿实验，两种方法对气溶胶质量增长的时间趋势的预测与观测结果不一致；在当天早些时候的高湿度条件下尤其如此。在此基础上，提出了一种新的SOA生成机理，该机理包括：1)半挥发性产物的气相反应和以容纳系数为主要传输参数的动态分配方法；2)由于极性物质吸收到颗粒水相中而形成的另一条生成SOA的途径。新的机制改进了预测的SOA大规模重现所有实验的观测结果。由于这些更改是专门针对SOA模块中的现有算法进行的，因此只需进行最小的修改即可更新空气质量模型以利用此方法。
Current air quality model (AQM) systems use either an Odum-type two-product or a volatility basis set (VBS) approach to predict secondary organic aerosol (SOA) formation from toluene oxidation. For the SOA module in AQM systems, the stoichiometric and partitioning coefficients used in both these approaches are typically developed from laboratory studies conducted in a single chamber, under a limited set of conditions (e.g., low humidity and initial (NH4)2SO4seed), and with an implicit assumption of instantaneous thermodynamic equilibrium. In this study, we evaluated independent toluene laboratory studies that include experiments with different combinations of initial toluene, NOx, non-SOA-forming hydrocarbon mixture, initial seed type, and humidity. When evaluated against this observational data set both the Odum-type and VBS approaches fail to predict observed SOA when tested under dry conditions, in the presence of the hydrocarbon mixture, and with low initial seed mass, regardless of seed type. For wet experiments, predictions of temporal trends in aerosol mass growth from both approaches are inconsistent with observations; this is especially true earlier in the day under high humidity conditions. Based on these findings, a new SOA mechanism is developed that includes: 1) gas-phase reaction of semi-volatile products and a dynamic partitioning approach with accommodation coefficient as the principal transport parameter, 2) an additional pathway of SOA formation due to uptake of polar species into the particle aqueous-phase. The new mechanism improves predicted SOA mass reproducing observations from all experiments. Since these changes were made exclusively to existing algorithms in SOA modules, minimal modifications would be required to update air quality models to utilize this approach.