Impact of biomass burning on haze pollution in the Yangtze River Delta, China: a case study in summer 2011

Abstract

Abstract. Open biomass burning is an important source of air pollution in China and globally. Joint observations of air pollution were conducted in five cities (Shanghai, Hangzhou, Ningbo, Suzhou and Nanjing) of the Yangtze River Delta, and a heavy haze episode with visibility 2.9–9.8 km was observed from 28 May to 6 June 2011. The contribution of biomass burning was quantified using both ambient monitoring data and the WRF/CMAQ model simulation. It was found that the average and maximum daily PM2.5 concentrations during the episode were 82 μg m−3 and 144 μg m−3, respectively. Weather pattern analysis indicated that a stagnant process enhanced the accumulation of air pollutants, while the following precipitation process scavenged the pollution. Daily minimum mixing depth during the stagnant period was below 50 m. Both observation data and CMAQ model simulation indicated that biomass open burning contributed 37% of PM2.5, 70% of organic carbon and 61% of elemental carbon. Satellite-detected fire spots, back-trajectory analysis and air model simulation can be integrated to identify the locations where the biomasses are burned. The results also suggest that the impact of biomass open burning is regional, due to the substantial inter-province transport of air pollutants. These findings would improve the understanding of not only heavy haze and air pollution episodes, but also the emissions of such open fires.