基于Model-3/CMAQ模式的本溪市大气细颗粒物数值模拟

为探究北方山区城市大气细颗粒物污染特征，应用气象模式WRF耦合空气质量模式CMAQ对本溪市2016年PM_2.5空间分布特征、化学组分特征及主要污染源贡献情况进行分析.本溪市SO₂、NO_x、TSP的工业排放量分别达到5.2×104、4.1×104、16.1×104 t.结果表明，模拟值与监测值变化趋势基本一致，模拟效果较好. 1月ρ（PM_2.5）明显高于7月，空间分布均呈现"西高东低"态势，高值区出现在人口稠密的市区附近. 1月ρ（PM_2.5）本地源贡献率表现为钢铁（35.7%）>供暖（12.5%）>居民（7.5%）>移动（5.2%）>秸秆（2.0%）>电力（0.4%）；7月为钢铁（48.6%）>移动（9.2%）>建材（3.5%）>居民（2.8%）>电力（1.5%）.受气候、地貌及大气污染物排放特征影响，1月区域传输特征明显，外来源贡献为24%，高于7月的14%.另外，1月和7月本溪市PM_2.5组分中二次粒子（SO₄2-、NO₃-、NH₄+）占比分别为29%和32%，碳组分（OC、EC）占比分别为43%和37%，碳气溶胶污染严重.研究显示，本溪市大气细颗粒物污染具有明显的季节性变化特征，1月部分区域浓度超标主要是由于以钢铁行业为主的工业排放造成，加之本溪市1月以西北风为主且风力较大，市区位于西部低海拔地区，来自中部城市群的污染物在向东南方向传输过程中受到高海拔山区阻隔，从而形成污染物积聚效应. 

A Numerical Study of PM2.5 Pollution in Benxi City based on Model-3/CMAQ

To investigate the pollution characteristics of fine particulate matter in the northern mountain cities, the research adopts Weather Research and Forecasting Model (WRF) in combination with Congestion Mitigation and Air Quality Model (CMAQ) to analyze the spatial distribution characteristics, chemical constituent and the main contributed pollutant sources of PM_2.5 in Benxi City for the year 2016. The industrial pollution of SO₂, NO_x, and TSP in Benxi City are 5.2×104, 4.1×104, and 16.1×104 tons respectively. According to the result, the simulation value and the monitoring value change trend are basically consistent. Therefore the simulation results are reliable. PM_2.5 concentration of Benxi City in January is obviously higher than that in July; the spatial distribution of PM_2.5 in west area is higher than that in east area. The high-concentration area occurs in populated main city. The main contribution of PM_2.5 concentration in January is Steel (35.7%)>Heating (12.5%)>Resident (7.5%)>Mobile (5.2%)>Straw (2.0%)>Electricity (0.4%); On the other hand, Steel (48.6%)>Mobile (9.2%)>Concrete (3.5%)>Resident (2.8%)>Electricity (1.5%) in July. Affected by climate, landscape and characteristics of pollutant distribution, transmission is obvious in January, external source contribution is 24%, which is higher than that in July (14%). Besides, the secondary particles of PM_2.5 (SO₄2-, NO₃-, NH₄+) in Benxi City occupy 29% and 32% in January and July, carbon components(OC, EC) occupy 43% and 37%, Carbon aerosols pollution is heavy. PM_2.5 air pollution in Benxi City illustrates obvious seasonal variation. Concentration in partial region of January exceeds the standard mainly due to industrial emissions (especially steel industry).In addition, the city of Benxi was dominated by the northwest wind and the wind was strong in January. The city is located in the low-altitude area of the west. The pollutants from the central urban agglomeration are blocked by high altitude in the south-eastern direction, that lead to the pollutant concentration increase.