2021年一次春季北方沙尘过程对广州空气质量的影响

Influence of a northern dust weather process on air quality of Guangzhou in spring 2021

2021年3月,中国北方地区发生了大范围的沙尘天气,广州出现了连续3 d都以PM_(10)为首要污染物的罕见现象.为进一步加深关于北方粗粒子气溶胶传输对广州市空气质量影响的理解,本文利用广东省广州生态环境监测中心站的污染物与气象监测数据,结合富集因子法、特征雷达图和后向轨迹法分析了沙尘影响前后广州市大气污染特征的转变.结果表明:沙尘影响期间,(1)粗细粒子浓度比(PM_(2.5)/PM_(10))呈明显下降趋势,从沙尘影响前的0.59降低至0.27,广州市的污染特征由标准型、偏钢铁型转变为偏扬尘型;(2)大气颗粒物中Si、Fe、Ca、Pb、Al、Cu、K浓度显著升高,增幅超过50%,这7种元素的富集因子也显著升高,说明其污染源主要来自于粗颗粒气溶胶的长距离输送;(3)大气颗粒物中Zn和Mn浓度增长不明显,增幅均低于50%,V、Cr、Ni、As的浓度有所降低,这6种元素的富集因子也有所降低,说明其污染源主要来自于广州本地;(4)广州本次污染特征的转变受到源于蒙古国、中国内蒙古西部及南疆盆地的粗离子气溶胶远距离输送和本地生成的共同影响,反映了在大气颗粒物污染不断改善的新形势下,仍需关注北方沙尘对广州市空气质量的影响.本研究为广州市环境污染精细化治理与预警预报提供了理论依据.

In March 2021,an extensive dust storm occurred in northern China.Moreover,there was a rare phenomenon that PM_(10)became the primary pollutant in Guangzhou.To further understand the impact of the coarse particle aerosol transported from northern China on air quality in Guangzhou,we analyzed the change of air quality pollution characteristics in Guangzhou before and after the influence of dust by using the pollutant and meteorological monitoring data of Guangzhou Ecological Environment Monitoring Central Station,combined with the enrichment factors,characteristic radar charts and backward trajectory method.We found that the ratio of PM_(2.5)to PM_(10)concentration(PM_(2.5)/PM_(10))significantly dropped from 0.59 to 0.27,and the air pollution characteristic radar charts of Guangzhou changed from the types of standard and steel to dust.The analysis of chemical composition revealed that the concentration of Si,Fe,Ca,Pb,Al,Cu,and K in atmospheric particulate matter increased significantly by more than 50%,and the enrichment factors of these seven elements also increased significantly,indicating that they were mainly from the long-distance transport of coarse particle aerosols.The Zn and Mn concentrations were not significantly increased,both lower than 50%.The concentrations of V,Cr,Ni,and As had negative growth rates,and the enrichment factors of these six elements decreased,indicating that they were mainly originated from local pollutants in Guangzhou.We concluded that the dust particles,which may age at Mongolia,western Inner Mongolia and southern Xinjiang Basin,together with the local pollutants,were responsible for the change of air pollution characteristics in Guangzhou.Our results indicate that we should still pay attention to the intrusion of dust particles from outside Guangzhou under the new situation of atmospheric particulate matter(PM)pollution being greatly improved.This study provides an important theoretical base for the refined air pollution control and air quality forecast in Guangzhou.