不同季节天津市PM2.5与O3潜在源区及传输路径分析

为探究天津市各季节PM_2.5与O₃污染的非本地源贡献情况，本文以2017—2019年为研究时段，应用HYSPLIT模型，基于MeteoInfo软件对不同季节气流后向轨迹进行聚类分析，通过计算潜在源贡献因子(potential source contribution function, PSCF)、浓度权重轨迹(concentration-weighted trajectory, CWT)对天津市PM_2.5与O₃污染的外来潜在源区以及可能的污染传输途径进行研究. 结果表明:①天津市PM_2.5和O₃污染均较为严重，且具有明显季节性特征. 天津市各季节的气流变化明显，春、秋两季以西南方向气流为主，夏季以来自渤海的气流为主，冬季则以西北方向气流为主. ②天津市西南方向气流在各季节对应的污染物浓度均较高，春、秋两季西南方向气流携带的ρ(PM_2.5)和O₃浓度8 h滑动平均值〔简称“ρ(O₃-8 h)”〕均最高；夏季，西南方向气流携带的ρ(O₃-8 h)最高；冬季，西南方向轨迹携带的ρ(PM_2.5)最高. ③西南方向上河北省南部的邯郸市，山东省西部的菏泽市、聊城市，以及河南省北部的开封市、濮阳市、新乡市均为天津市PM_2.5与O₃污染的主要潜在源区. 此外，冬季张家口市和唐山市对天津市PM_2.5污染的潜在影响也较大. 冬季影响天津市PM_2.5污染的外来潜在源区情况较为复杂，除西南气流外，其还受西北部与东部气流的影响. 研究显示，天津市大气污染区域联防联控需重点关注河北省南部、河南省北部以及山东省西部城市的潜在输送影响. 

Analysis of Potential Source Areas and Transport Pathways of PM2.5 and O3 in Tianjin by Season

To explore the contribution of non-local sources of PM_2.5 and O₃ pollution in Tianjin in various seasons, the PM_2.5 and O₃ pollution in Tianjin from 2017 to 2019 was studied. First, the backward trajectory in different seasons was calculated based on the HYSPLIT model. Next, the potential source areas and possible pollution transmission routes of PM_2.5 and O₃ in Tianjin were analyzed using MeteoInfo software and cluster analysis, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) methods. The results showed that: (1) The airflow in Tianjin varies significantly from season to season. The southwest flow is dominant in spring and autumn. The flow from the Bohai Sea is dominant in summer, and the northwestern flow is dominant in winter. (2) The southwestern airflow in Tianjin corresponds to higher pollutant concentrations in all seasons. In spring and autumn, both ρ(PM_2.5) and ρ(O₃-8 h) (8 h sliding average of O₃ concentrations) carried by the southwestern airflow are highest. In summer, the highest ρ(O₃-8 h) is carried by the southwest flow. In winter, the highest ρ(PM_2.5) is carried by the southwest flow. (3) In the southwestern direction, the southern city of Handan in Hebei Province, the western city of Heze and Liaocheng in Shandong Province, and the northern city of Kaifeng, Puyang and Xinxiang in Henan Province are the main potential source areas for PM_2.5 and O₃ pollution in Tianjin. In addition, the potential impact of Zhangjiakou and Tangshan City on PM_2.5 pollution in Tianjin during winter is also high. The external potential source areas affecting PM_2.5 pollution in Tianjin in winter are complex, which is influenced by northwestern and eastern airflow in addition to southwestern airflow. Based on all the above research results, coordinated inter-regional PM_2.5 and O₃ prevention and control efforts of Tianjin should focus on the transportation of air pollutants from those cities in southern Hebei Province, northern Henan Province, and western Shandong Province.