2019年秋冬季京津冀与周边地区污染传输特征分析

本研究结合大气环境观测数据,应用潜在源分析法(PSCF)和浓度权重轨迹分析法(CWT),以及基于WRF-CMAQ模式的传输矩阵和传输通量计算方法,研究分析了2019年秋冬季京津冀典型城市的大气污染特征与成因,量化评估了京津冀地区与周边省份之间的PM_2.5传输贡献.结果表明,京津冀地区冬季较秋季污染严重,且重污染时段PM_2.5浓度均与相对湿度呈显著的正相关,和风速呈显著的负相关;京津冀典型城市北京、天津和石家庄的潜在源区主要分布在京津冀本地、山西、内蒙古中部地区和山东地区,这与CWT结果基本吻合.京津冀各省域的PM_2.5以本地排放贡献为主,北京、天津和河北的本地贡献率范围为54.33%~66.01%,京津冀受区域外传输的贡献率范围为0.11%~26.54%.传输通量结果表明,冬季PM_2.5的传输主要受高空西北气流的作用,尤其清洁天气,高风速驱动清洁气团流入;秋季则主要受低空东南气流作用;传输通量呈现出显著的垂直分布特征,高空区域传输作用更为活跃,传输通量的流入/流出以及垂直分布与污染级别和RH呈现非线性响应关系,主导风向变化导致重污染前的传输效应明显大于重污染期间,高湿环境的传输效应明显小于低湿环境.

Pollution transport characteristics of Beijing - Tianjin - Hebei region and its surrounding areas in January 2019

In this study, combined with atmospheric environment observation data, potential source analysis (PSCF) and concentration weight trajectory analysis (CWT), as well as transport matrix and transport flux calculation methods based on WRF-CMAQ model, were used to analyze the characteristics and causes of air pollution in typical cities in Beijing-Tianjin-Hebei in autumn and winter of 2019, and to quantitatively evaluate the characteristics and causes of air pollution in the Beijing-Tianjin-Hebei region and surrounding provinces between PM_2.5 transmission contribution. The results show that the Beijing-Tianjin-Hebei region is more polluted in winter than in autumn, and PM_2.5 concentration has a significant positive correlation with relative humidity and a significant negative correlation with wind speed during heavy pollution periods. The potential source regions of Typical Beijing-Tianjin-Hebei cities Beijing, Tianjin and Shijiazhuang are mainly distributed in Beijing-Tianjin-Hebei, Shanxi, central Inner Mongolia and Shandong, which is basically consistent with CWT results. In the Beijing-Tianjin-Hebei region, local emission contributed most to PM_2.5 emissions. The local contribution of Beijing, Tianjin and Hebei ranged from 54.33% to 66.01%, and the contribution of transmission from outside the Beijing-Tianjin-Hebei region ranged from 0.11% to 26.54%. Transport flux results show that PM_2.5 transport in winter is mainly influenced by upper-level northwest airflow, especially in clean weather, where high wind speed drives air mass inflow. In autumn, it is mainly affected by low level southeast airflow. The inflow/outflow and vertical distribution of transport flux show a non-linear response relationship with pollution level and RH. The dominant wind direction changes lead to a significantly larger transport effect before heavy pollution than during heavy pollution, and a significantly smaller transport effect in high RH than in low RH.