Investigation on emission factors of particulate matter and gaseous pollutants from crop residue burning.

Emission factors of particulate matter (PM), element carbon (EC), organic carbon (OC), SO2, NO(x), CO, CO2, and ten ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO2-, NO3-, SO4(2-)) were estimated from the domestic burning of four types of commonly produced crop residues in rural China: rice straw, wheat straw, corn stover, and cotton stalk, which were collected from the representative regions across China. A combustion tower was designed to simulate the cooking conditions under which the peasants burned their crop residues in rural China, to measure the emission factors. Results showed that wheat straw had the highest emission factor for the total PM (8.75 g/kg) among the four crop residues, whereas, corn stover and wheat straw have the highest emission factor for EC (0.95 g/kg) and OC (3.46 g/kg), respectively. Corn stover also presents as having the highest emission factors of NO, NO(x), and CO2, whereas, wheat straw, rice straw, and cotton stalk had the highest emission factors of NO2, SO2, and CO, respectively. The water-soluble ions, K+ and Cl-, had the highest emission factors from all the crops. Wheat straw had a relatively higher emission factor of cation species and F-, Cl-, NO2- than other residues.