Articles | Volume 16, issue 15
Research article
02 Aug 2016
Research article |  | 02 Aug 2016

Impact of crop field burning and mountains on heavy haze in the North China Plain: a case study

Xin Long, Xuexi Tie, Junji Cao, Rujin Huang, Tian Feng, Nan Li, Suyu Zhao, Jie Tian, Guohui Li, and Qiang Zhang

Abstract. With the provincial statistical data and crop field burning (CFB) activities captured by Moderate Resolution Imaging Spectroradiometer (MODIS), we extracted a detailed CFB emission inventory in the North China Plain (NCP). The WRF-CHEM model was applied to investigate the impact of CFB on air pollution during the period from 6 to 12 October 2014, corresponding to a heavy haze incident with high concentrations of PM2.5 (particulate matter with aerodynamic diameter less than 2.5 µm). The WRF-CHEM model generally performed well in simulating the surface species concentrations of PM2.5, O3 and NO2 compared to the observations; in addition, it reasonably reproduced the observed temporal variations of wind speed, wind direction and planetary boundary layer height (PBLH). It was found that the CFB that occurred in southern NCP (SNCP) had a significant effect on PM2.5 concentrations locally, causing a maximum of 34 % PM2.5 increase. Under continuous southerly wind conditions, the CFB pollution plume went through a long-range transport to northern NCP (NNCP; with several mega cities, including Beijing, the capital city of China), where few CFBs occurred, resulting in a maximum of 32 % PM2.5 increase. As a result, the heavy haze in Beijing was enhanced by the CFB, which occurred in SNCP. Mountains also play significant roles in enhancing the PM2.5 pollution in NNCP through the blocking effect. The mountains blocked and redirected the airflows, causing the pollutant accumulations along the foothills of mountains. This study suggests that the prohibition of CFB should be strict not only in or around Beijing, but also on the ulterior crop growth areas of SNCP. PM2.5 emissions in SNCP should be significantly limited in order to reduce the occurrences of heavy haze events in the NNCP region.

Short summary
We studied the impact of crop field burning (CFB) on air pollution in North China Plain (NCP) using MODIS observations and the numerical model WRF-CHEM. The CFB plume emitted in southern NCP and went through a long-range transport to northern NCP. The long-range transport and the effect of mountains obviously enhanced the PM2.5 pollution in northern NCP. The prohibition of CFB should be strict not just in or around Beijing, but also on the ulterior crop growth areas of southern NCP.
Final-revised paper