不同季节肇庆市PM2.5和O3污染特征及潜在源区分析

为定量化评估不同地区对肇庆市污染物输送影响，分析了2014—2018年肇庆市ρ（PM_2.5）和ρ（O_{3-8 h}）（O_{3-8 h}为O₃日最大8 h滑动平均值）的变化特征，并基于HYSPLIT模式计算不同季节后向气流轨迹，通过聚类分析、潜在源贡献因子和浓度权重轨迹方法对肇庆市外来污染物的输送路径和潜在源区进行分析.结果表明:①2014—2018年肇庆市ρ（PM_2.5）年均下降3.3 μg/m3，2016年开始ρ（PM_2.5）最大值逐年增大.ρ（PM_2.5）日变化呈双峰型，峰值分别出现在上、下班高峰期后.2016年起ρ（O_{3-8 h}）年均增加4.4 μg/m3，成为肇庆市首要空气污染物.ρ（O₃）日变化呈单峰型，于15:00—16:00达到峰值.②PM_2.5和O₃污染分别在冬季和秋季较严重，超标日分别达20.6和15.0 d.ρ（PM_2.5）与风速相关性最高，ρ（O_{3-8 h}）与日照时数和相对湿度相关系数均较高.③春、夏两季影响肇庆市的气流近80%来自南部海面和东北方向，秋、冬两季85%以上气流源自偏东和偏北方向，肇庆市PM_2.5和O₃污染除受本地排放影响外，还有来自珠三角、广东省北部及其东部沿海、江西省等地区的输送贡献.研究表明，肇庆市PM_2.5和O₃污染均较严重，区域联防联控需重点关注广东省中东部城市的外来输送影响. 

Characteristics and Potential Sources of PM2.5 and O3 in Different Seasons in Zhaoqing City

In order to quantitatively assess the relative impact of different areas of Zhaoqing City on the transportation of air pollutants, this study analyzed the characteristics of PM_2.5 and O₃ pollution variations over 2014-2018, and the transport path, potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) for the pollutants were explored by trajectory cluster based on the HYSPLIT model. The results showed that: (1) The annual mean PM_2.5 concentration in Zhaoqing City experienced a downward trend of 3.3 μg/m3 from 2014 to 2018, with intensified extreme values since 2016. While the diurnal variations of the PM_2.5 were characterized by double peaks, which occurred in the time after the rush hour. Meanwhile, the annual mean O₃ concentration showed an upward trend of 4.4 μg/m3 during 2016-2018, which was the primary pollutant. The O₃ concentration showed a single-peak characteristic, mainly existing during 15:00 to 16:00. (2) The most severe PM_2.5 (O₃) pollution appeared in winter (autumn), with above-normal days of 20.6 (15.0). The variation of PM_2.5 concentration was highly correlated with wind speed, while O₃ was closely related to the insolation duration and relative humidity. (3) In spring and summer, airflow from the south and northeast explained about 80% of the total trajectories. However, in autumn and winter, the airflows from the north or east were more important, accounting for more than 85%. In addition to the impact of local emissions, the potential pollution sources affecting Zhaoqing City's PM_2.5 and O₃ included the Pearl River Delta, northern Guangdong Province, coastal areas of eastern Guangdong Province and Jiangxi Province. The results showed that PM_2.5 and O₃ pollutions were serious, and coordinated inter-regional prevention and control efforts should focus on the transportation of air pollutants from the central and eastern areas of Guangdong Province.