北京市大气细颗粒物污染时空分布特征及其降水清除影响

Spatial and temporal distribution of fine particulate matter pollution and scavenging effect of precipitation in Beijing

研究2017—2019年北京市大气细颗粒物(PM_(2.5))的时空分布特征,并探讨降水过程对PM_(2.5)的湿清除作用。结果表明:(1)研究期间北京市PM_(2.5)逐年下降,2019年(41.79μg/m^(3))达到最低;冬、春季更易出现严重污染,其中冬季更易发生PM_(2.5)污染。(2)北京市PM_(2.5)浓度呈现南部>北部的空间分布特征,其中南部郊区站点污染最严重。(3)影响PM_(2.5)湿清除的首要因素是降水前3 h PM_(2.5)浓度,其次是过程累积降水量和最大小时降水量。降水前3 h PM_(2.5)质量浓度为>75~115μg/m^(3)、过程累积降水量为>25~50 mm、最大小时降水量为>10~25 mm时的降水过程对PM_(2.5)湿清除效果最佳。降水持续时间对PM_(2.5)湿清除的影响相对最低且为负影响。

The spatial and temporal distribution of fine particulate matter(PM_(2.5))in Beijing during 2017-2019 was studied,and the wet scavenging effect of precipitation on PM_(2.5) was also discussed.The results showed that:(1)during the study period,PM_(2.5) decreased year by year in Beijing,and reached the lowest level in 2019(41.79μg/m^(3)).Severe pollution was more likely to occur in winter and spring and PM_(2.5) pollution was more likely to occur in winter.(2)The spatial variation of PM_(2.5) in Beijing was characterized by southern>northern and PM_(2.5) concentration was significantly highest in southern suburb.(3)Wet scavenging effect on PM_(2.5) was mostly influenced by PM_(2.5) concentration 3 h before precipitation,followed by the total accumulated precipitation and the maximum hourly precipitation.The precipitation process had the best wet scavenging effect on PM_(2.5) when PM_(2.5) mass concentration 3 h before precipitation was>75-115μg/m^(3),total accumulated precipitation was>25-50 mm and the maximum hourly precipitation was>10-25 mm.The impact of precipitation duration on wet scavenging was relatively minimal and negative.