Abstract Recent updates to U.S. regulatory guidelines for modeling impacts of single sources to secondary pollutants, such as ozone (O3) and fine particulate matter (PM2.5), require the use of established photochemical models with a complete treatment of gas-phase and aerosol chemistry as the preferred method for a Tier 2 demonstration approach. Such models include photochemical grid models (PGMs), as well as Lagrangian puff models with the requisite treatment of processes governing the formation of secondary pollutants from their precursors. SCICHEM is an open source reactive puff model that includes treatments for gas, aerosol, and aqueous-phase chemistry that are comparable to those in PGMs. The dispersion component of SCICHEM is based on the state-of-the-science puff model, SCIPUFF (Second-order Closure Integrated Puff). The model is a valuable tool that requires fewer resources and setup cost to run than PGMs to calculate the impacts of a single source or a small number of sources on downwind ozone and PM2.5. This paper describes a model inter-comparison study of secondary pollutant impacts due to emissions from a hypothetical coal-fired power plant stack. The models compared in this study include SCICHEM and the two most commonly used PGMs, CMAQ and CAMx. Stacks are located in 4 separate regions of the U.S. with distinct differences in chemical environments and geographical features. The key inputs (hypothetical stack parameters and emission rates, meteorology) to the three models are based on a common dataset for consistency. The source impacts calculated by the PGMs are based on zero-out simulations (i.e., with and without the source of interest) as well as the source apportionment tools available in CAMx, while SCICHEM directly predicts source impacts in a single simulation. Annual simulations are conducted to determine the frequency distribution of source impacts over the 4 regions. The comparison of model results shows both similarities and differences in the frequencies and magnitudes of peak impacts predicted by the three models. There is good agreement among all models in their predictions of 98th and 99th percentile impacts.

中文翻译：

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使用拉格朗日反应性烟团模型的单一源对二次污染物的影响：与光化学网格模型的比较

摘要 美国监管指南的最新更新，用于模拟单一来源对臭氧 (O3) 和细颗粒物 (PM2.5) 等二次污染物的影响，需要使用已建立的光化学模型，并对气相和气溶胶进行完整处理。化学作为方法 2 示范方法的首选方法。此类模型包括光化学网格模型 (PGM)，以及拉格朗日抽吸模型，其中对控制从其前体形成二次污染物的过程进行了必要的处理。SCICHEM 是一种开源反应性抽吸模型，包括与 PGM 中的处理相当的气体、气溶胶和水相化学处理。SCICHEM 的分散组件基于最先进的粉扑模型 SCIPUFF（二阶闭包集成粉扑）。该模型是一种有价值的工具，与 PGM 相比，它需要更少的资源和设置成本来计算单个源或少量源对顺风臭氧和 PM2.5 的影响。本文描述了对假设燃煤电厂烟囱排放造成的二次污染物影响的模型比对研究。本研究中比较的模型包括 SCICHEM 和两种最常用的 PGM，CMAQ 和 CAMx。Stacks 位于美国 4 个独立的地区，化学环境和地理特征有明显差异。三个模型的关键输入（假设的烟囱参数和排放率、气象）基于一个通用数据集以保持一致性。PGM 计算的源影响基于置零模拟（即，有和没有感兴趣的源）以及 CAMx 中可用的源分配工具，而 SCICHEM 在单个模拟中直接预测源影响。进行年度模拟以确定源影响在 4 个区域的频率分布。模型结果的比较显示了三个模型预测的峰值影响的频率和幅度的相似性和差异。所有模型对 98% 和 99% 影响的预测都具有良好的一致性。模型结果的比较显示了三个模型预测的峰值影响的频率和幅度的相似性和差异。所有模型对 98% 和 99% 影响的预测都具有良好的一致性。模型结果的比较显示了三个模型预测的峰值影响的频率和幅度的相似性和差异。所有模型对 98% 和 99% 影响的预测都具有良好的一致性。