Rethinking the causes of extreme heavy winter PM2.5 pollution events in northern China
Rethinking the causes of extreme heavy winter PM2.5 pollution events in northern China
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DOI：
10.1016/j.scitotenv.2021.148637
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发表时间：
2021-07-06
影响因子：
9.8
通讯作者：
Yao, Xiaohong
中科院分区：
文献类型：
--
作者：
Liu, Xiaohuan;Chang, Ming;Yao, Xiaohong
据报道，空气质量模型在很大程度上低估了中国严重污染事件期间的PM2.5浓度。利用Models-3社区多尺度空气质量模式（CMAQ）对2013年5 - 6月（非采暖期）和11 - 12月（采暖期）中国北方地区PM2. 5浓度进行了模拟，重点分析了PM2. 5浓度低估的原因。模拟结果在青岛市非采暖期和采暖期中约有50%的时段（称为好时段）重现了PM2. 5的质量浓度，而在其余时段（称为差时段）模拟效果不理想。在这方面，高估的无机盐和低估的有机物在PM2.5中相互抵消，导致在良好的时期，在一个很好的模拟PM2.5浓度，而在贫困时期，行星边界层高度，风向，降水和其他因素的偏差造成模拟和观测PM2.5浓度之间的不一致。敏感性研究表明，低估主要排放颗粒物的本地排放可能是在重霾天PM2.5预测不足的主要原因。此外，我们的研究结果表明，在空气质量模型中的气体-气溶胶热力学平衡的条件的假设可能会导致过高的二次PM2.5无机盐（SO 42- + NO3- + NH 4+）在晴朗的日子。相反，在重污染或重霾天，高浓度的空气污染物理论上迅速导致气/粒化学平衡，SO 42-、NO3-和NH 4+浓度没有高估。然而，在重霾天的主要排放颗粒物从本地源的低估还有待解释，需要进一步调查。(C)2021爱思唯尔有限公司版权所有。
It has been reported that air quality models largely underestimate PM2.5 concentrations during severe pollution events in China. In this study, the Models-3 Community Multi-scale Air Quality model (CMAQ) was employed to simulate PM2.5 concentrations in May-June (non-heating period) and in November-December (heating period) of 2013 in northern China, with a particular focus on determining the causes of the underestimation. Modeling results reproduced the mass concentrations of PM2.5 in approximately 50% of the non-heating and heating pe-riods in Qingdao (referred to as the good periods), while the model performance was unsatisfactory during the remaining periods (the poor periods). In this respect, the overprediction of inorganic salts and the underprediction of organic matter in PM2.5 canceled each other out and resulted in a good simulation of PM2.5 concentrations during the good periods, whereas during poor periods, the bias of the planetary boundary layer height, wind direction, precipitation, and other factors caused inconsistencies between the simulated and ob-served PM2.5 concentrations. Sensitivity studies showed that the underestimation of primarily emitted particles from local emissions was likely the main cause of PM2.5 underpredictions during heavy haze days. Furthermore, our results implied that the assumption of the conditions of the gas-aerosol thermodynamic equilibria in the air quality model likely results in an overprediction of secondary PM2.5 inorganic salts (SO42- + NO3- + NH4+) during clear days. In contrast, during heavy pollution or heavy haze days, high concentrations of air pollutants theoret-ically rapidly leads to gas/particle chemical equilibrium and no overprediction of SO42-, NO3-, and NH4+ concen-trations. Nevertheless, the underestimation of primarily emitted particles from local sources during heavy haze days is yet to be explained and needs further investigation. (C) 2021 Elsevier B.V. All rights reserved.