Abstract:
Abstract: China is a vast agricultural country which produces a large amount of crop straw. If the crop straw was used irrationally, the airborne pollutant concentration would increase, and the soil moisture and organic matter content would reduce. It does harm to ecological environment. Beijing-Tianjin-Hebei region is the political, economic and cultural center of China and plays an essential role in the development of social economy of China. There are severe environment problems occurring in this region such as smog happening frequently. Burning of crop straw is concerned to be one of the main reasons for the smog in this region. The research of crop straw resource was carried out in the Beijing-Tianjin-Hebei region aimed to promote the comprehensive utilization of crop straw. The production and utilization of crop straw resources and their application potential were evaluated and analyzed. Furthermore, the emission characteristics of gaseous pollutants generated from open burning of major crop straw in the region were quantitatively estimated that. The results showed that the theoretical amount of crop straw in the Beijing-Tianjin-Hebei region was 5.4×107 t in 2012, and the main crop species were corn and wheat straw. Crop straw resources could be used as high quality fertilizer with high contents of nitrogen (N), phosphorus (P) and potassium (K), and the amounts were 3.7×104, 7.4×104 and 1.0×106 t for N, P and K respectively. Straw returned to field was the major utilization method for crop residue in the Beijing-Tianjin-Hebei region. However, the returned amounts were accounting for 67.7%, 27.3% and 61.2% of the total crop residue amounts in Beijing, Tianjin and Hebei respectively. Interestingly, the returned amount of wheat residue in Beijing was accounting for 94.5%, which was higher than Hebei (78.5%) and Tianjin (47.1%). The amount of wasted and burned straw accounted for 1.7%, 0.5% and 1.4% respectively in Beijing, Tianjin and Hebei. The nutrient resource such as N, P and K of crop straw returned to soil in the Beijing-Tianjin-Hebei region was 2.4×104, 1.9×104 and 6.1×105 t, respectively. However, there was still a large amount of crop straw abandoned or open burned. Wheat and maize residue were the major crop residue open burned in the region, which accounted for 93.0% of the total straw amount open burned. In Hebei, 14.9% and 31.8% of total straw resource were abandoned and open burned respectively, while 8.2% and 5.9% in Tianjin, and 0.6% and 0.8% in Beijing. According to the statistical data, 8.7×104 t CO, 9.6×105 t CO2, 2.5×102 t NO2, 5.5×102 t NO and 8.1×102 t NOx from open burning of wheat and maize straw were emitted to atmosphere in Hebei Province, which were as three times as that in Tianjin City. Due to farmers' high cognitive level and policy of government, a very small amount of straw was open burned in Beijing, and only 1.2×103 t CO, 1.3×104 t CO2, 4.3 t NO2, 8.5 t NO and 12.8 t NOx were emitted to atmosphere due to open burning of straw. The total amounts of pollutants emitted from wheat and maize straw open burning were 1.0×106 and 4.8×105 t, respectively. According to regional straw resource endowment and utilization potential, county (township) should be the unit to develop the "5 kinds of material" technology strategy based on the local conditions. What's more, system supporting policy measures should be formulated and taken based on straw returning mechanism, use mechanism out of the field, organization and management mechanism, and technology research and development mechanism.