Polychlorinated dibenzo-p-dioxins and dibenzofurans emissions from open burning of crop residues in China between 1997 and 2004.

Annual emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from open burning of crop residues in each province of China mainland between 1997 and 2004 were estimated to be ranged from 1.38x10(3) to 1.52x10(3) g I-TEQ/yr, with the average of 1.50+/-0.08x10(3) g I-TEQ/yr, which contributed to approximately 10% approximately 20% of the total emissions in China. The PCDD/F emissions mainly occurred in the largest crop-producing provinces, especially in those of higher economic levels. The major sources of PCDD/F emissions from open burning in China were found to be cereal residues (i.e. rice, wheat, and corn), which accounted about 70% of the total emissions. Moreover, the first-order one-variable grey differential equation model (GM (1,1) model) for annual emissions of PCDD/Fs was established based on grey system theory. The GM (1,1) model was proved to be robust to predict the annual PCDD/F emissions from crop residue field burning in forthcoming years.