Impacts of Emissions From Crop Residue Open Burning in Hebei on the Air Quality of the Beijing-Tianjin-Hebei Region

Crop residue open burning (CROB) is an important emission source in China. Hebei is a major agricultural province, and it is of great significance to study its emission characteristics and impacts on the air quality of the Beijing-Tianjin-Hebei (BTH) region. Based on the bottom-up method, the high temporal (day) and spatial (1 km×1 km) emission inventory of CROB in Hebei was developed in 2014, and the spatial-temporal characteristics were further analyzed. Furthermore, based on the emission inventory, fire spots data and WRF-CAMx-PSAT model, the impacts of CROB emissions on the air quality of BTH region was studied and analyzed of June and October. Results show that the emissions of SO₂, NO_x, PM₁₀, PM_2.5, NMVOC, NH₃, CO, EC, OC, CO₂ and CH₄ from CROB in Hebei in 2014 were 0.3×10⁴, 1.9×10⁴, 5.1×10⁴, 5.0×10⁴, 4.6×10⁴, 0.3×10⁴, 27.3×10⁴, 0.2×10⁴, 2.1×10⁴, 685.3×10⁴ and 2.0×10⁴ t, respectively. Corn and wheat were primary contributors to the emission, and the emission fraction was 46.6%-71.4% and 20.5%-47.8%, respectively. Two monthly emission peaks were found in June and October, and the emission in June was the highest among all the year, accounting for 26.9% of the total emission. Daily emissions fluctuated greatly, and the top value happened in the end of June (0.3×10⁴ t) and early November (0.2×10⁴ t). In June and October, the average contribution ratios of CROB emissions to atmospheric PM_2.5, EC, SO₂ and NO₂ concentrations in the BTH region were 4.2% and 5.5%, 2.6% and 2.8%, 0.4% and 0.5%, and 2.5% and 1.9%, respectively. Except NO₂, the contribution ratios of other pollutants in October were all higher than those in June. Affected by the characteristics of straw burning, the daily-scale contribution showed obvious fluctuation characteristics. The highest contributions from the emission of CROB in Hebei to the daily PM_2.5 concentration of Beijing, Tianjin and Hebei can reach 25.7%, 23.1% and 21.0%, respectively.