Carbonaceous aerosol emissions from household biofuel combustion in China.

Field measurements were conducted in four representative rural areas across China to determine carbonaceous aerosol emissions from combustion of household biofuel. Results showed that the size distribution of both black carbon (BC) and organic carbon (OC) peaked at 0.26-0.38 microm. OC accounted for a significant fraction of fine particles from wheat residue combustion across all size categories, whereas both BC and OC accounted for a significant fraction of fine particles from fuel wood combustion across all size categories. The emission factors for crop wastes are 0.43 +/- 0.32 and 1.93 +/- 1.00 g/kg for BC and OC, respectively. The emission factors for woody fuel were 1.49 +/- 0.69 g/kg and 1.13 +/- 0.40 g/kg for BC and OC, respectively. Woody fuel BC-to-PM2.5 ratios were significantly higher than the ratios from crop waste, ranging from 36.40 to 71.18%, relative to crop waste BC-to-PM2.5 ratios which ranged from 1.70 to 33.52%. Woody fuel also had high BC-to-OC ratios, ranging from 0.95 to 2.51. Woody fuel combustion accounts for approximately two-thirds of China's estimated 430 Gg of BC emissions and crop waste combustion accounts for approximately 80% of China's 922 Gg of OC emissions from household biofuel combustion in 2005.