基于MM5/CALPUFF的乌鲁木齐市“煤改气”工程大气污染物浓度空间变化数值模拟

Spatial changes of air pollutants distributions before and after the“coal to gas”project in Urumqi based on numerical simulation with MM5 and CALPUFF Models

运用MM5/CALPUFF模型,模拟"煤改气"工程前后不同情境下分析乌鲁木齐市供热企业采暖期间主要大气污染物浓度及分布空间变化的变化。依照环境普查和环境统计数据,以燃煤锅炉排放数据为依据,选择空气质量模型CALPUFF进行情景设计模拟。通过预测,以燃煤量>1 000 t·a-1及所有供热企业为排放源,SO2、NOx日均浓度分别下降66.85%、91.53%,年均浓度分别下降73.89%、81.03%,对PM2.5、PM10浓度改善效果有限。"煤改气"项目的实施,使大型采暖锅炉能源结构发生了根本性改变,乌鲁木齐市大气污染类型已由煤烟型向机动车尾气混合型转化。不同区域降幅存在着差异,污染物年均消减市南区<市中区<市北区。

In this paper,the MM5/CALPUFF model was used to simulation the coal combustion pollutants emission and their spatial distribution before and after the Urumqi＂Coal to Gas＂project. Two scenarios were set based on Urumqi local energy structure adjustment project： one is taking the heating enterprises as the only emission source in 2010 and 2014,and the other is taking the enterprises in which the coal consuming was more than1 000 tons/year and all the heating enterprises as the emission sources in 2010 and 2014. Prediction of the environmental air quality was conducted during the heating period（October-March）. The results show that,in situation one,the daily concentration of SO2,NOx,PM10 and PM2.5 fell by 92.44%,97.52%,90.56% and 88.80%,respectively,and the annual average concentration fell by 74.66%,94.93%,89.50% and 92.31% respectively. This indicates that after the project,the heating enterprise emissions concentration decreased obviously. In situation two,the daily concentration of SO2 and NOx fell by 66.85% and 91.53% respectively,and the annual average concentration fell by 73.89% and 81.03% respectively,the effect of PM2.5 and PM10 improved finitely. According to＂Xinjiang environmental quality statement（2000、2014）＂,annual average concentration of SO2,NOx and PM10 in2010 fell by 71.9%,16.41% and-9.77%,respectively,compared with those in 2010. The measured data of SO2 and PM10agreed well with the prediction. The reduction of NOxwas offset because the number of motor vehicles in Urumqi increased quickly in recent years. The＂coal to gas＂project has made radical changes in the energy structure of large heating boiler,which improved the atmospheric environment in Urumqi to a certain extent. Atmospheric pollution has changed from coal burning to mixed automobile vehicle exhaust emission. The annual amount of pollution reduction average concentrations in different districts changed greatly due to the natural causes and adjustment of the city layout. The annual amount of pollution reduction increased successively from south area（Urumqi County and Dabancheng District）,middle area（Saybagh District,Tianshan District,Shuimogou District and New Urban District and Toutunhe District）to north area（Midong District）. Based on the numerical simulation of MM5 and CALPUFF models,different situation models were established to study the spatial changes of characteristic pollutants distributions before and after the＂Coal to Gas＂project in Urumqi for the first time. The research is of great practical significance for controlling and tackling the Urumqi pollution problem.