Taheri Ahmad, Khorsandi Babak, Alavi Moghaddam Mohammad Reza
Department of Civil and Environmental Engineering, Amirkabir University of Technology (Tehran Polytechnic), 350 Hafez Avenue, Tehran, 159163-4311, Iran.
Sci Rep. 2025 Jan 20;15(1):2521. doi: 10.1038/s41598-024-82709-9.
Oxidant (OX), the sum of ozone (O) and nitrogen dioxide (NO), is used to determine nitrogen oxides (NO)-independent regional contribution and NO-dependent local contribution. This study investigates OX trends and its local and regional levels in Tehran, Iran using the data from 21 monitoring stations from 2012 to 2022 and satellite remote sensing data (TROPOMI) for 2022. The spatiotemporal trends of O, NO, and OX are first examined using ground-based and remote sensing data, and then the polar plots are employed to identify the dominant directions of OX transport and its sources. Subsequently, the local and regional contributions of OX were determined using OX-NO relationship. The findings indicated that the OX trend is primarily affected by O fluctuations during the warmer months, whereas NO variations have a stronger correlation with OX during the remaining months. The emissions from the central zone of the city were mostly caused by the transportation fleet. The emissions from industries in the south also have a significant effect on the city's OX concentration. Moreover, the local contribution of OX, reaching a maximum value of 0.15 ppb/ppb NO (for both monthly and yearly analysis), contributes to the elevation of OX levels during nighttime. In contrast, the OX local contribution at daylight hours is mostly negative, with minimum values of - 0.15 ppb/ppb NOx for July and - 0.07 ppb/ppb NO for 2012, indicating a decrease in the OX concentration with an increase in the local NO emission. Furthermore, the OX levels, especially for daylight hours, is mostly related to its regional contribution with maximum of 100 ppb in July and 95 ppb in 2017, suggesting the necessity of considering regional emissions in developing mitigation scenarios. Lastly, our results indicate that the transportation fleet plays an undeniable role in contributing to the local emissions in Tehran.
氧化剂（OX）是臭氧（O）和二氧化氮（NO）的总和，用于确定与氮氧化物（NO）无关的区域贡献和与NO相关的本地贡献。本研究利用2012年至2022年21个监测站的数据以及2022年的卫星遥感数据（TROPOMI），调查了伊朗德黑兰的OX趋势及其本地和区域水平。首先使用地面和遥感数据检查O、NO和OX的时空趋势，然后使用极坐标图确定OX传输的主要方向及其来源。随后，利用OX-NO关系确定OX的本地和区域贡献。研究结果表明，在较温暖的月份，OX趋势主要受O波动的影响，而在其余月份，NO变化与OX的相关性更强。该市中心区域的排放主要来自运输车队。南部工业排放对城市的OX浓度也有显著影响。此外，OX的本地贡献在夜间达到最大值0.15 ppb/ppb NO（月度和年度分析均如此），导致OX水平升高。相比之下，白天时段OX的本地贡献大多为负，7月最小值为-0.15 ppb/ppb NOx，2012年最小值为-0.07 ppb/ppb NO，表明随着本地NO排放增加，OX浓度降低。此外，OX水平，尤其是白天时段的水平，大多与其区域贡献有关，7月最大值为100 ppb，2017年为95 ppb，这表明在制定减排方案时需要考虑区域排放。最后，我们的结果表明，运输车队在德黑兰本地排放中发挥了不可忽视的作用。
