Quantification of crop residue burning in the field and its influence on ambient air quality in Suqian, China

In China, many pollutants are released because of crop residue burning in the field, resulting in serious pollution of ambient air. Suqian with 4523 km2 of total area under cultivation was selected as a case to be studied, where wheat–rice double cropping system is widely adopted. Based on the data of crop output from 2001 to 2005, the annual average amount of crop residue generated was estimated as 3.04×106 t. About 82% of wheat straw and 37% of rice straw were burned in the field, so the proportion of crop residue burned in the field was about 43%. In combination with emission factors proposed by some literatures, the total amounts, the amounts in summer harvest and in autumn harvest of TSP, PM10, SO2, NOx, NH3, CH4, EC, OC, VOC, CO, and CO2, emitted from crop residue burning in the field, were estimated. The total amounts of them were 11,051, 7572, 525, 3280, 1707, 3544, 905, 4331, 20,606, 120,747, and 1,988,376 t, respectively, and about 78% of them were emitted in summer harvest. During the summer harvest from June 4 to 13 in 2006, influenced by crop residue burning in the field, the daily average concentrations of PM10, NO2, and SO2 were 0.266, 0.051, and 0.063 mg m−3, respectively. And the daily average concentration of PM10 kept exceeding 0.250 mg m−3, the Third Standard Level of National Ambient Air Quality (China). Based on hourly concentration changes of PM10 and meteorological condition, crop residue burning in the field was characterized. According to the field survey, it is regarded that combine harvester acts as an important role in crop residue burning in the field.