Abstract. In the urban environment, gas such as nitrogen dioxide NO₂, and particles impose adverse impacts on pedestrians’ health. The conventional computational fluid dynamics (CFD) methods that regard pollutant as passive scalar cannot reproduce the formation of secondary pollutants, such as NO₂ and secondary inorganic and organic aerosols, leading to uncertain prediction. In this study, SSH-Aerosol, a modular box model that simulates the evolution of gas, primary and secondary aerosols, is coupled with the CFD software OpenFOAM and Code_Saturne. The transient dispersion of pollutants emitted from traffic in a street canyon is simulated using unsteady Reynolds-averaged Navier–Stokes equations (RANS) model. The simulated concentrations of NO₂, PM₁₀ and black carbon are compared with field measurements on a street of Greater Paris. The simulated NO₂ and PM₁₀ concentrations based on the coupled model achieved better agreement with measurement data than the conventional CFD simulation. Meanwhile, the black carbon concentration is underestimated, probably partly because of the underestimation of non-exhaust emissions (tyre and road wear). Vehicles are considered the main source of ammonia (NH₃) in urban environments, which may condense with nitric acid (HNO₃) to form ammonium nitrate. In the reference simulation with NH₃ traffic emissions accounting for 1–2 % of NOx emissions, aerosol dynamics leads to an ammonium nitrate increase of 46 % on average over a 12-hour simulation period (5 a.m. to 5 p.m.) compared to the conventional CFD simulation. Furthermore, an increase in NH₃ traffic emissions (to 10 % and 20 % of NOx emissions) may leads to a large increase in ammonium nitrate (35 % and 55 %) compared to the reference simulation. In addition, aerosol dynamics leads to a 52 % increase in 12-hour time-averaged organic matter concentrations compared to the conventional CFD simulation, because of the condensation of anthropogenic compounds from precursor-gas emissions and of background biogenic precursor-gases on the enhance inorganic concentrations.

中文翻译：

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通过化学反应、气溶胶动力学和 CFD 的耦合模拟模拟街道尺度的污染物扩散

摘要。在城市环境中，二氧化氮NO ₂等气体和颗粒物对行人的健康造成不利影响。传统的将污染物视为被动标量的计算流体动力学（CFD）方法无法再现二次污染物（如NO ₂和二次无机和有机气溶胶）的形成，导致预测不确定。在本研究中，SSH-Aerosol 是一种模拟气体、初级和次级气溶胶演化的模块化盒模型，与 CFD 软件 OpenFOAM 和 Code_Saturne 相结合。使用非定常雷诺平均纳维-斯托克斯方程 (RANS) 模型模拟街道峡谷中交通排放的污染物的瞬态扩散。_{NO 2}的模拟浓度、PM ₁₀和黑碳与大巴黎街道上的现场测量结果进行比较。基于耦合模型模拟的 NO ₂和 PM ₁₀浓度与测量数据的一致性优于传统的 CFD 模拟。同时，黑碳浓度被低估，部分原因可能是低估了非废气排放（轮胎和道路磨损）。车辆被认为是城市环境中氨（NH ₃）的主要来源，它可能与硝酸（HNO ₃）冷凝形成硝酸铵。在使用 NH _{3的参考模拟中}交通排放量占 NOx 排放量的 1-2%，与传统 CFD 模拟相比，气溶胶动力学导致硝酸铵在 12 小时模拟期间（上午 5 点至下午 5 点）平均增加 46%。此外，与参考模拟相比，NH ₃交通排放量的增加（达到 NOx 排放量的 10% 和 20%）可能会导致硝酸铵的大幅增加（35% 和 55%）。此外，与传统的 CFD 模拟相比，气溶胶动力学导致 12 小时时间平均有机物浓度增加 52%，这是因为前体气体排放中的人为化合物和背景生物前体气体在增强无机浓度。