Seasonal variation of mass absorption efficiency of elemental carbon in the four major emission areas in China

Abstract

As an important site-specific optical parameter widely used in climate models, the mass absorption efficiency (MAE) of elemental carbon (EC), varies dramatically with the source types and governs the direct radiative forcing (DRF) estimation. In this study, the MAE of EC for ambient samples collected from four major emission areas in China, i.e., Beijing-Tianjin-Hebei area (BTH), Yangtze River Delta area (YRD), Sichuan Basin area (SB), and Pearl River Delta area (PRD), as well as emissions from burning of residential honeycomb briquette, firewood and rice straw were investigated by using a filter-based method. The annual mean MAEEC over the four major emission areas is 7.51 m2/g.MAEEC in BTH and YRD during summer appears significantly higher than MAEEC in other seasons, while seasonal variations of MAEECin SB and PRD suggest MAEEC in summer and autumn is higher than that in winter and spring. MAEEC for samples from fossil fuels burning and biomass open-burning is 2.10 times higher than that from residential biofuel burning, which could be one of the reasons for the higher MAEEC values during the seasons heavily affected by fossil fuels burning and biomass open-burning (i.e., summer and autumn) than winter for the four locations. Difference between the measured and AeroCom median value of MAEEC may cause underestimation of DRFEC over the studied area by a factor of 0.13. Spatial and temporal variations of MAEEC would also result in underestimations of DRFEC to different degrees varying with seasons and areas.