Regional discrepancies in spatiotemporal variations and driving forces of open crop residue burning emissions in China.

As a major source of secondary organic aerosol, open crop residue burning (OCB) emits a large number of trace gases and particulates to the atmosphere. Extensive OCB is detected during harvest seasons in most regions of China. Emissions from OCB have been widely investigated in China, but few studies have focused on regional discrepancies in spatiotemporal variations with a long timescale. In this study, emissions from OCB in three typical regions of China, including Northeast China, Chengdu-Chongqing and Guangdong, from 2003 to 2016, were estimated using a combination of statistical data and the Moderate Resolution Imaging Spectroradiometer (MODIS) observations, and regional discrepancies in spatiotemporal variations and driving forces were analyzed in detail. The results showed that OCB emissions of CO and PM2.5 in 2016 were 3.63 × 106 and 6.96 × 105 tons in Northeast China, 9.77 × 105 and 1.36 × 105 tons in Chengdu-Chongqing, and 1.24 × 105 and 1.19 × 104 tons in Guangdong, respectively. The OCB emissions in Northeast China maintained an overall increasing trend, which were mainly dominated by rural economic development and agricultural modernization, with great potential for reduction. In Chengdu-Chongqing, emissions increased until 2013 and then decreased, due to the impact of policies prohibiting OCB. In Guangdong, emissions showed annual fluctuations with a slightly decreasing trend influenced by metrological conditions and related policies. The analysis of the driving forces behind the regional discrepancies among these typical regions indicated that OCB emissions in China were characterized by uneven rural economic development, control policies, and natural conditions, suggesting that region-dependent control measures are needed for reducing OCB emissions. This study provided a better understanding of OCB emission characteristics in the three typical regions and revealed the diversity of OCB emission characteristics in China.