中文摘要：

乌鲁木齐市冬季采暖期大气污染严重，SO2浓度呈现不断增加的趋势，超标频率逐年增多，已成为不容忽视的环境问题。2012年乌鲁木齐市实施“煤改气”工程，旨在改善乌鲁木齐市的大气环境质量。工程的实施是否对SO2浓度的控制起到决定性的作用？文中选用改造后的冬季采暖期（10月15日～翌年4月15日），采用ThermoScientificTEOM1405-F连续监测仪对SO2日均浓度值进行不间断的监测采样，并对“煤改气”前后城市不同区域的SO2日均浓度变化进行了分析。结果显示：“煤改气”对SO2浓度的降低效果显著，但降低幅度在区域间存在差异，“煤改气”前冬季SO2日均浓度普遍存在超标国家二级环境质量标准的现象，全市不同区域超标率在25％～40％之间；“煤改气”工程实施后，冬季SO2日均浓度在空间上呈现出由南向北逐渐增加的态势，市南（中）区SO2日均浓度基本达标，而北面SO2浓度虽有降低，但超标频率依然较高，值得当地政府在环境治理过程中关注。

英文摘要：

Air pollution of Urumqi is a very serious issue, especially in winter due to the high emissions from resi- dential heating. In past decades, the concentration of SO2 was increased rapidly, which becomes an environmental problem that can not be ignored. Although the Government has taken a series of measures such as desulfurization, the increasing coal consumption leads to the concentration of SO2 remaining high, which still seriously impacts the quality of atmospheric environment. In order to improve the serious air pollution in winter thoroughly, the local gov- ernment has implemented energy structure adjustment work, the “coal to gas” project. Whether the project played a decisive role to control concentration of SO2？ The aim of this paper is to investigate the situation of the most serious pollution period of winter （1-2 months） in 2009 and 2013, and analyze the change of daily average of SO2 concen- tration before and after “coal to gas” in different areas of the city. The daily average of SO2 concentration data were analyzed by using Thermo Scientific TEOM 1405-F continuous monitor. The results show that after the project the daily average of SO2 concentration decreases obviously, but the declines are differences in the different regions. Be- fore project “coal to gas”, the daily average of SO2 concentration generally exceeded the States Concentration Limit Class 2 Standard （0.15 mg.m-3）. In southern and middle areas of city, the SO2 exceeded the rates from 25 to 40% in different areas of the whole city. After the project, from the south to the north, the daily average of SO2 concentration increased gradually in winter. Substituting coal by gas would reduce SO2 emissions by 65.9%, 69.6% and 48.8%, re- spectively. In the south and middle areas, the daily average of SO2 concentration can reach the States Concentration Limit Class 2 Standard; in the north area, the concentration of SO2 was decreased, but it was often higher than that of the States Concentration Limit Class 2 Standard. The s