Emission characteristics of carbonaceous particles and trace gases from open burning of crop residues in China

Open burning of crop residue is an important source of carbonaceous pollutants, and has a large impact on the regional environment and global climate change. Laboratory burn tests were conducted using a custom-made combustion chamber to determine pollutants (i.e. CO₂, CO, PM_2.5, organic carbon (OC) and elemental carbon (EC)) emission factors (EFs) of wheat straw, rice straw and corn stalk; the three major agricultural crop residues in China. The average EFs were estimated to be 1351 ± 147 g kg^-1 for CO₂, 52.0 ± 18.9 g kg^-1 for CO, 10.6 ± 5.6 g kg^-1 for PM_2.5, 4.8 ± 3.1 g kg^-1 for OC and 0.24 ± 0.12 g kg^-1 for EC. In addition, the effect of fuel moisture was investigated through the controlled burning of wheat straw. Increasing the moisture content decreased the CO₂ EF, and increased the EFs of CO, PM_2.5 and OC. Based on measurements from this study and nationwide statistics in crop type and area, pollutants emission inventories for crop residue combustion with 1° × 1° resolution were compiled for 2008. Total emissions were 120 Tg CO₂, 4.6 Tg CO, 0.88 Tg PM_2.5, 0.39 Tg OC and 0.02 Tg EC.