2015~2021年景洪市PM2.5的传输路径及潜在源区

分析2015~2021年景洪市大气污染特征,识别日均PM_2.5浓度超过国家空气质量二级标准所在月(超标月)。利用混合单粒子拉格朗日积分轨迹模型计算景洪市PM_2.5超标月的逐日72h后向轨迹,并结合景洪市PM_2.5浓度,通过聚类、潜在源区贡献因子和浓度权重轨迹因子等分析方法,识别景洪市日均PM_2.5超标月的主要传输路径和潜在源区。结果表明:景洪市2~5月为日均PM_2.5超标月;景洪市2~5月PM_2.5的传输主要来自其西向、西南和南向,且中短距离和低空传输对应高PM_2.5浓度;景洪市PM_2.5源区主要位于缅甸中部、老挝西北部和泰国北部;通过归一化处理浓度权重轨迹因子可知,景洪市2~5月PM_2.5传输的源区主要来自缅甸,贡献41%~50%,其次为泰国和老挝,分别为21%~27%和5%~12%。基于2015~2021年2~5月中南半岛火点数分布及与景洪市PM_2.5浓度相关性分析,进一步揭示影响景洪市PM_2.5的主要排放源为缅甸生物质开放燃烧。研究可为景洪市建立跨境区域联防联控措施以及未来气候变化研究提供指导。

Analysis of transport pathways and potential source regions of PM2.5 in Jinghong from 2015 to 2021

This study analyzed the characteristics of air pollutants in Jinghong City from 2015 to 2021, and obtained the months when the daily PM_2.5 exceeded the Class-2limit values of the National Ambient Air Quality Standard (NAAQS). Based on Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, 72-hour daily backward trajectories in those months were calculated, combined with PM_2.5 concentration, the transport pathways and potential source regions during those months in Jinghong city were determined through the methods of analysing cluster, potential source contribution factor and concentration weighted trajectory factor. The results shown that the months of PM_2.5 exceeding standard were concentrated on February, March, April and May in Jinghong City. The transport pathways of PM_2.5 during February to May in Jinghong City mainly originate from west, southwest and south, with medium and short-range, and low-altitude transports corresponded to high concentration of PM_2.5 pollution. The potential source regions of PM_2.5 in Jinghong during February to May were mainly located in the central region of Myanmar, the northwest region of Laos and the northern region of Thailand. The results of normalized concentration weighted trajectory factor exhibited that the source regions of PM_2.5 in Jinghong City during February to May were concentrated in Myanmar, accounting for 41%~50%, with Thailand and Laos accounting for 21%~27%, 5%~12%, 2% and 2%, respectively. To further investigate the sources of the PM_2.5 in Jinghong, the distribution of fires counts in the indo-China and its correlation with PM_2.5 in Jinghong from 2015 to 2021 were analyzed. Further results demonstrated that the main source of PM_2.5 in Jinhong city during February to May was open biomass burning from Myanmar. These results in this study have guiding significance for Jinghong city to establish cross-border regional joint prevention and control measures and to study future climate change.