太原市采暖初期大气PM_(2.5)质量浓度变化分析

Mass concentration variation of urban fine particulate matter in initial stage of heating period in Taiyuan

目的了解采暖初期太原市大气PM_(2.5)污染状况,探讨燃煤增加对城市大气PM_(2.5)质量浓度的影响。方法记录和整理太原市9个监测点2014年10月(采暖前)和11月(采暖后)的大气SO2、NO2、CO、O3、PM_(10)、PM_(2.5)浓度小时值和日均值,采用单因子污染指数评价相关分析和小波分析等方法研究大气PM_(2.5)质量浓度的变化规律及影响因素。结果采暖前后大气常规污染物的单因子污染指数均以PM_(2.5)最大,采暖开始后的约两周内大气PM_(2.5)日均质量浓度未超过GB 3095—2012《环境空气质量标准》规定的二级标准限值,但从11月17日开始其质量浓度明显升高,超标严重。除O3外,PM_(2.5)与PM_(10)、SO_2、NO_2、CO浓度的小时值及日均值均有一定的相关关系,且采暖后相关系数高于采暖前;各污染物经4层小波分解滤波后的时间序列变化图和小波方差图表明PM_(2.5)、PM_(10)、SO_2、NO_2和CO的浓度变化趋势一致,而与O_3浓度的变化不同。结论城市大气PM_(2.5)污染的形成受多种因素作用,采暖期燃煤增加的影响在累积到一定程度且有不利气象条件出现时会导致大气PM_(2.5)污染。

Objective To investigate the air pollution derived from urban fine particulate matter（PM2.5） in the initial stage of heating period in Taiyuan, Shanxi province, China and assess the influence of coal-burning on the mass concentrations of atmospheric PM2.5. Methods Based on the hourly mass concentrations of conventional air pollutants（i.e. SO2, NO2, CO, O3,PM（10） and PM2.5） in October and November of 2014 at nine regular monitoring stations in Taiyuan, the daily concentrations of each air pollutant on average were calculated and then analyzed by using the methods of single factor pollution index assessment, correlation analysis and wavelet analysis. Results Both before and after heating period, the single factor pollution index of PM2.5was the highest compared with other pollutants; in the initial half of November, the daily mean values of PM2.5did not exceed the secondary standard limits prescribed in Ambient Air Quality Standard（GB 3095-2012）, but its concentration increased significantly after Nov. 17. Except for O3, the hourly and daily mean values of PM2.5were related to those of PM（10）,SO2, NO2 and CO, with larger correlation coefficients after heating than before heating. The time series analysis and wavelet variance calculations also indicated that the PM2.5concentration had a similar changing trend to those of PM（10）, SO2, NO2 and CO concentrations, but different to O3 concentration. Conclusion Urban PM2.5pollution is disturbed by many factors. It occurs when the emissions of air pollutants from coal-burning are increased continuously under the adverse meteorological conditions.