2021年冬季四川盆地区域PM_(2.5)重污染事件成因及来源解析

Attribution and source apportionment of a severe PM_(2.5) episode in winter 2021 over the Sichuan Basin

利用WRF-CMAQ模型及来源解析模块ISAM对2021年11月1~20日四川盆地一次区域PM_(2.5)重污染过程进行了数值模拟,结合地面气象观测数据和污染物监测数据分析了污染成因机制并进一步开展了PM_(2.5)来源解析研究.结果表明,WRF-CMAQ模型能较好地重现气象要素及各城市污染物浓度的变化.此次冬季PM_(2.5)污染过程因受本地排放源及小风、高湿等不利气象条件的影响,导致PM_(2.5)在成都平原累积,在短时间内达到峰值而形成,并且多个城市日均PM_(2.5)浓度峰值超过150μg/m^(3).ISAM源解析结果表明,本地源是四川盆地各城市PM_(2.5)污染的主导来源,其中成都、重庆、达州及广元的本地排放对PM_(2.5)浓度的贡献率均超过50%,而周边城市的区域输送也有重要贡献.

In this study,the Weather Research and Forecasting(WRF)-Community Multiscale Air Quality(CMAQ)model with ISAM module was adopted to simulate a highly polluted PM_(2.5) episode across the Sichuan Basin between November 11and November 20 in 2021.In combination with ground-level meteorological observations and air quality monitoring data,the formation mechanism of this episode and sources of PM_(2.5) were elucidated.The results show that the variations of meteorological parameters and air pollutants concentrations were well captured by the WRF-CMAQ model.This PM_(2.5) episode was mainly affected by local emissions and unfavorable meteorological conditions featured by low wind speeds and high relative humidity,resulting in the accumulation of PM_(2.5) in the Chengdu Plain,which progressively reached its peak in a short period.The peak daily average PM_(2.5) concentration in multiple cities exceeded 150μg/m^(3).Further analysis performed by ISAM indicates that local anthropogenic emissions were the dominant source of PM_(2.5) in cities within the Sichuan Basin,with a contribution higher than 50%depicted in Chengdu,Chongqing,Dazhou,and Guangyuan cities.Regional transport from nearby regions also played an important role in elevating PM_(2.5) levels.