合肥市冬季大气NO2污染特征及模拟研究

Characteristics and Simulation of Atmospheric NO_2 Concentration in Winter of Hefei City

基于合肥市NO_2浓度逐时监测数据,分析了该地区冬季大气NO_2污染的时空变化特征;并在主要大气污染源调查的基础上,构建了污染源排放清单,利用CALPUFF模型对NO_2浓度的动态变化进行了模拟。结果表明:合肥市大气NO_2浓度除个别点超标外,基本在《环境空气质量标准》(GB3095-2012)二级标准限值内。受主导风向和污染源位置影响,合肥市大气NO_2浓度以东北、西南部较高;浓度日变化呈典型的双峰型分布,早晚出现峰值,午后出现谷值,并且在休息日表现出污染浓度下降、日变化趋缓的"周末效应"。CALPUFF模型对NO_2浓度的空间分布格局总体把握较好,并且对其逐日变化具有比较可靠的模拟能力,模拟值与监测值的相关系数达0.7,模型对工作日的模拟效果略优于休息日。在研究时段内合肥市区面源对大气NO_2污染浓度贡献最为显著。

Spatial-temporal variation characteristics of atmospheric NO2 concentration were analyzed by using the NO2 monitoring data in Hefei City. On the basis of the investigation of main air pollution sources,the NO2 emission inventory was established. CALPUFF model was then used to simulate the temporal and spatial variation of NO2 concentration in Hefei.Result indicated that higher concentration in the northeast and southwest of Hefei dominated the spatial distribution characteristics of NO2 pollution,owing to the dominant wind direction and pollution source location. The diurnal variation of NO2 concentration exhibited significant double-peaked pattern,with the peak value appeared in the morning and evening.The ＂weekend effect＂was found in the variation of NO2 pollution,which was characterized by the lower pollution concentration and the weaker diurnal variation. Comparison of simulated and observed NO2 concentration suggested that CALPUFF model could well simulate the spatial pattern of NO2 pollution in Hefei. Further the simulated temporal variation was consistent with the observation,and the correlation coefficient between daily simulated and observed concentration reached 0.7. Without concerning to the weekend effect,the model simulation show larger bias at weekends than working days. During the study period,the urban area source had the most contribution to the atmospheric NO2 pollution concentration in Hefei.