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 MAEEC in 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.
Highlights
Light-absorbing carbon (LAC) is getting much more attentions from researchers and policy-makers for its considerable effect on global and regional climate change (Chung and Seinfeld, 2005; Ramanathan and Carmichael, 2008), air quality and human health (Jansen et al, 2005; Suglia et al, 2008), and its reduction has been targeted for near-term global warming mitigation (Shindell et al, 2012)
The mass absorption efficiency (MAE) of elemental carbon (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
Seasonal patterns of MAE of elemental carbon (MAEEC) over the four areas can be classified into two types: MAEEC in summer is significantly higher than MAEEC in other times (BTH and YRD, Fig. 3), and MAEEC in summer and autumn higher than MAEEC in winter and spring (SB and PRD, Fig. 4)
Summary
Light-absorbing carbon (LAC) is getting much more attentions from researchers and policy-makers for its considerable effect on global and regional climate change (Chung and Seinfeld, 2005; Ramanathan and Carmichael, 2008), air quality and human health (Jansen et al, 2005; Suglia et al, 2008), and its reduction has been targeted for near-term global warming mitigation (Shindell et al, 2012). Elemental carbon (EC) derived from thermal-optical methods is recommended to be used in air quality and source. Mass absorption efficiency (MAE) is a widely used optical parameter of aerosol particles, which is usually calculated from the light absorption coefficient divided by the mass concentration. MAE is a key factor to derive radiative forcing of aerosol particles in climate models, and its values range from 2.3 to 18 m2/g (Koch et al, 2009; Jacobson, 2012). Quinn and Bates (2005) conducted a series of intensive experiments with identical sampling and analysis protocols and gave values of MAE of elemental carbon (MAEEC) ranging from 6 to 20 m2/g. Reported work on the MAEEC in rural and urban sites in India suggests higher MAEEC values in urban areas (Ram and Sarin, 2009). According to a study conducted in Xiamen, MAEEC in suburban areas was only one third of that in urban
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