Abstract
Although a many studies concerning crop residue burning have been conducted, the influence of crop residue burning on local PM2.5 concentrations remains unclear. The number of crop residue burning spots was the highest in Heilongjiang province and we extracted crop residue burning spots for this region using MOD14A1 (Thermal Anomalies & Fire Daily L3 Global 1 km) data and national land cover data. By analyzing the temporal variation of crop residue burning and PM2.5 concentrations in Heilongjiang province, we found that the total number of crop residue burning spots was not correlated with the variations of PM2.5 concentrations at a provincial (regional) scale. However, crop residue burning exerted notable influence on the variations of PM2.5 concentrations at a local scale. We experimented with a set of buffer zone radiuses to examine the influencing area of crop residue burning. The results suggest that the valid influencing area of crop residue burning was between 50 and 80 km. The mean PM2.5 concentration measured at stations close to crop residue burning spots was more than 60 μg/m3 higher than that measured at stations not close to crop residue burning spots. However, no consistent, significant correlation existed between the existence of crop residue burning spots and local PM2.5 concentrations, indicating that local PM2.5 concentrations were influenced by a diversity of factors and not solely controlled by crop residue burning. This research also provides suggestions for better understanding the role of crop residue burning in local and regional air pollution.
Highlights
Since the outbreak of a severe haze episode in Beijing in December 2012, regional and national haze episodes have been frequently witnessed across China in recent years
With increasing haze episodes caused by crop residue burning, massive studies have been conducted to quantify the total emission of crop residue burning at the regional and national scale [7,8,9] and evaluate the emission of in-situ crop residue burning [9,10,11,12,13,14,15]
By analyzing the temporal variation of crop residue burning and PM2.5 concentrations, we found that the total number of crop residue burning spots, even during the period with the most burning spots, was not correlated with variations of PM2.5 concentrations at the provincial scale
Summary
Since the outbreak of a severe haze episode in Beijing in December 2012, regional and national haze episodes have been frequently witnessed across China in recent years. Many studies [1,2,3,4] have been conducted to analyze sources of PM2.5 concentrations in different cities and have shown that emission sources such as traffic, coal burning, biomass burning, cooking, dust related emissions, industrial pollution, and secondary inorganic aerosol all contributed significantly to variations of PM2.5 concentrations. In addition to these sources, the contribution of crop residue—materials left over from the production of crops—burning to local and regional haze episodes has been widely discussed recently. Compared with traffic, industry emissions, and other major emission sources, few in-depth studies on the quantitative influences of crop residue burning on the variations of local and regional PM2.5 concentrations have been conducted
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