The Impact Of Biomass Burning Over Beijing-Tianjin-Hebei Region On Air Quality In Beijing

Open biomass burning makes up an important part of the total global emissions of greenhouse gases, trace gases and particulate matter. Although episodic and highly variable, open biomass burning can contribute to local, regional and global air quality problems and climate forcings. In recent years, particle pollution events caused by crop residue burning in China have drawn much attention. Crop residue burning, as the fourth type of biomass burning, emits plenty of aerosol particulate matter and pollution gases (CO, NOx, SO2, etc.), which can worsen air quality,degrade visibility, and influence our health and production under the unfavorable atmospheric conditions.A coupled meteorology and aerosol/chemistry model (WRF-Chem) with surface and satellite observation data is utilized to investigate the regional transport features,the spatial distribution and temporal variation of air pollutants, and the impact of biomass burning on air quality in Beijing during 7-11 October 2014 and on 15 June 2014, when the air pollution events occurred. Weather situations, surface meteorological characteristics, and locations of fire points are also analyzed. Surface meteorological variables and surface PM2.5 concentration in the North China are reproduced well by the model. Biomass burning emissions from local or regional source and unfavorable meteorological conditions intensify the haze pollution in Beijing and its surrounding areas.Using biomass burning emission inventory FINN within the WRF-Chem model,the two air pollution events are explored. The severe and persistent haze event (7-11 October 2014) reflects the influence of regional transport of air pollutants. Aerosol particles and gases of crop residue burning transport from northern Henan, southern Hebei, and western Shandong to Beijing and its surrounding areas by southerly wind.After considering biomass burning emission of FINN, the total emission of OC and PM2.5 during 5-8 October over the key high-fires and high-aerosol-concentration region increase by 56%, 37%, respectively. The weather situation in the North China and Huanghuai area is so stable that it is beneficial for the accumulation of the air pollutants. The contribution to surface PM2.5 concentration of biomass burning is highest over northern Henan, the source of crop residue burning, with the values of above 40%. The contribution in percentage of biomass burning to surface PM2.5 concentration, PM2.5 organic carbon, PM2.5 nitrate, PM2.5 ammonium, PM2.5 sulfate and PM2.5 black carbon in urban Beijing is 19.0%, 37.2%, 16.4%, 15.8%, 11.3%, 4.9%averaged during 7-11 October, respectively. The period of 15 June 2014 is primarily influenced by biomass burning emissions over southeastern Beijing. The contribution of biomass burning to surface PM2.5 concentration in Beijing is 30.1%, highest during 15:00-19:00 on 15 June. The biomass burning impacts on Shunyi, Huairou,urban area, Changping, Dingling from strongest to weakest, with the contribution of 62.7%,39.1%, 29.0%, 18.2%, 13.3% on 15 June.