Abstract
A heavy air pollution event occurred in Chengdu between 7 May 2014 and 8 May 2014. The present study established tracer sources based on HJ-1 satellite data, micropulse light detection and ranging (LiDAR) remote sensing data, and backward trajectories simulated using the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model. Additionally, the present study analyzed the diffusion conditions for the sources and characteristics of the pollutant transport in this pollution event through simulation using a mesoscale atmospheric chemistry transport model—the weather research forecasting model with chemistry (WRF–CHEM). The results show that the change in the boundary-layer height over Chengdu had a relatively large effect on the vertical diffusion of pollutants. During the pollution event, Chengdu, Meishan, and Leshan were areas of significantly low mean ventilation coefficients ( V H ). In Chengdu, the V H was extremely low at night, and there was a temperature inversion near the ground, resulting in the continuous accumulation of pollutants at night and a continuous worsening of the pollution. During the period of heavy pollution, there were straw-burning sites in Meishan, Ziyang, Neijiang, Zigong, and Deyang. On 7 May 2014, the pollutants in Chengdu mainly originated from Meishan. The accumulation in Chengdu of pollutants originating in Meishan and Deyang led to highly concentrated pollution on 8 May 2014, to which the pollutants originating in Deyang were the main contributor. The transport of pollutants resulting from straw burning in the study area and the relatively poor conditions for the pollutant diffusion in Chengdu collectively led to the heavy air pollution event investigated in the present study.
Highlights
A continuous rise in the frequency of heavy pollution events and a continuous increase in the area affected by heavy pollution has recently been observed in China; regional atmospheric environmental problems involving inhalable and fine particulate matter as the characteristic pollutants have become increasingly prominent and attracted extensive attention from all sectors of society.based on the current regional and complex characteristics of atmospheric pollution in China, it is necessary to strengthen the fundamental research on atmospheric pollution sources and regional pollution transport
65% of the particulate matter less than 2.5 μm in diameter (PM2.5 ) in Shijiazhuang and Xingtai had originated from local emissions and that the remainder originated from Shanxi and northern Hebei. He et al [3] analyzed a severe dust-haze pollution event that occurred in Beijing in 2013 through simulations using the weather research forecasting model with chemistry (WRF–CHEM) and noted that the relatively low wind speed and relatively low boundary layer were the main causes of the peak PM2.5 concentrations, and that the local pollution sources contributed to as much as 78% of this pollution event
Cheng et al [4] analyzed the sources of sulfur dioxide (SO2 ) in a heavy pollution event that occurred in Beijing based on the comprehensive air quality model with extensions and noted that external pollution sources contributed to as much as 83% of the SO2 concentration during this pollution event
Summary
A continuous rise in the frequency of heavy pollution events and a continuous increase in the area affected by heavy pollution has recently been observed in China; regional atmospheric environmental problems involving inhalable and fine particulate matter as the characteristic pollutants have become increasingly prominent and attracted extensive attention from all sectors of society. Zhu et al [5] analyzed an air pollution event that occurred in Nanjing and its surrounding area through the comprehensive use of satellite monitoring data, meteorological observation data, and a backward trajectory simulation model and observed that the atmospheric pollutants resulting from straw burning in central and northern Jiangsu was the main pollutant source of this event. Regarding these types of studies, two methods have been used in the literature.
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