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Crop Residue Burning Influence on the Air Quality over Nanjing and Surrounding Regions

Author: SuJiFeng
Tutor: ZhuBin
School: Nanjing University of Information Engineering
Course: Atmospheric Physics and Atmospheric Environment
Keywords: Nanjing and surrounding regions air quality emission source of crop residue WRF-CMAQ contribution rate O3
CLC: X131.1
Type: Master's thesis
Year: 2011
Downloads: 335
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Abstract

Wide range of primary gaseous compounds and particles (CO、SO2、NOx、O3 etc.) releasing from biomass burning and secondary gases and particles have a significant impact on air quality, atmospheric chemistry and climate on regional and global scales. China is a large agricultural country, which production of crop residue is very large. Yangtze delta is one of the highest levels of economic development region in China. The use of commercial energy is increasing and the use of biofuel is decreasing. As a result crop residue burning is increasing year by year. The pollution releasing from open crop residue burning affects the air quality under the unfavorable weather condition, and it makes the poor air quality of the city seriously.During the time period between Oct.28 to Oct.29,2008, a serious air pollution event took place in Nanjing and surrounding regions, accompanying with sharply increasing of PM10,CO and SO2 in the air. Satellite remote sensing data, surface meteorological observations, air pollution index and the NCEP reanalysis data were used to investigate the atmospheric conditions and planetary boundary layer (PBL) features. Air mass backward trajectory simulation method was employed to analyze the sources of the air pollutants and transport paths of this event. The results show that the transport of gas pollutants released from crop residue burning in the central and north parts of Jiangsu province, combining with unfavorable weather condition, which is the dominating reason of this air pollution episode. It is found there was a high-pressure system with relative uniform pressure pattern, weak vertical velocity, vorticity and divergence below 500 hPa, which prevents atmospheric ventilation. The inversion temperature, low mixing height and topographical forcing winds in the PBL are also not favorable for the diffusion and transport of the air pollutants.In addition to the original pollution source in 2001 made by David G. Streets which resolution is 0.1°×0.1°and pollution source in 2006 which resolutions is 0.5°×0.5°, we renew the anthropogenic resource; compute the crop residue burning source in Jiangsu, Anhui, Zhejiang province and Shanghai Municipality by estimating the straws of the three provinces and one municipality in 2008. The data of the crop yields in 2008 comes from yearbook of agricultural statistics of every city of the three provinces and one municipality. At last, the new pollution source was used for counting by model WRF-CMAQ.Aim at two processes that open crop residue burning affects air quality over Nanjing and surrounding regions, we compare the concentration of PM10 and CO which is simulated by model and the measured concentration. At the same time, we analysis on the contribution rate of pollution releasing by crop residue burning in the pollution of Nanjing by closing the emission source of different regions. The result shows that time-concentration curve of PM10 and CO are well responded the real emulation of pollution. The mean contribution rate of local region of Nanjing is the maximum of these different regions. And the second largest was the central and north parts of Jiangsu Province and Anhui Province. The mean contribution rate of the south of Jiangsu province and Zhejiang province is very little. Because the regions of Nanjing and surrounding are under VOCs control area, so when the concentration of NOx increases, the concentration of O3 decline on the contrary. The concentration of NOx simulated with the new emission increase in the two pollution events, and the concentration of VOCs has no significant change, the weather is against the photochemical reaction at the same time, so the concentration of O3 decline.

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CLC: > Environmental science, safety science > The basic theory for the Environment and Science > Environmental Chemistry > Environmental pollution, chemical > Air pollution chemistry
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