长春市大气SO2、O3和NOx的变化特征及来源

为研究长春市采暖期大气污染物的污染水平及其随时间的变化特征,于2012年1—6月通过在线监测仪获取了大气中ρ(SO₂)、ρ(O₃)和ρ(NO_x),利用HYSPLIT(混合型单粒子拉格朗日综合轨迹模式)后向轨迹模型结合地面气象资料,初步分析了该市大气污染物的可能来源及传输过程. 结果表明:观测期间ρ(SO₂)和ρ(NO_x)的日均值分别为(25.0±21.6)和(54.4±34.0)μg/m3,ρ(O₃)最大8 h平均值为(85.0±26.2)μg/m3,ρ(SO₂)、ρ(NO_x)和ρ(O₃)的变化范围分别为2.3~131.0、17.6~183.7和31.0~173.3 μg/m3；其中ρ(O₃)日均值超过GB 3095—2012《环境空气质量标准》二级标准限值的时间为2 d,ρ(SO₂)和ρ(NO_x)均未超过二级标准限值,但ρ(SO₂)日均值在采暖期超过GB 3095—2012一级标准限值的时间为23 d,占采暖期的24%. 采暖期ρ(SO₂)日变化为双峰型,峰值出现在06:00和20:00左右,而在非采暖期表现为单峰型,峰值出现在08:00左右；ρ(O₃)表现为单峰型,峰值出现在13:00─15:00；ρ(NO_x)在采暖期表现为双峰型,而在非采暖期表现为单峰型. 对观测期间72 h内HYSPLIT后向轨迹模拟结果和气象数据的分析表明,长春市大气污染主要受本地源的影响,偏西气流易对污染物造成积累,而偏东气流有利于污染物扩散. 

Pollution Characteristics and Sources of SO2, O3 and NOx in Changchun

Three criteria air pollutants (O₃, NO_x and SO₂) in Changchun were continuously observed during heating and non-heating seasons. Changchun is one of the major metropolitan areas in northeastern China. Long, cold weather leads to considerable pollutant emissions that, when combined with strong atmospheric inversion, may pose adverse effects on human health. However, the unique characteristics of air pollutants during heating and non-heating seasons in the region have not yet been well studied. Continuous measurements of major criteria air pollutants (SO₂, O3 and NO_x) were conducted from January 5th, 2012, to June 30th, 2012, at a monitoring station set up on the campus of the Institute of Geography and Agroecology (IGA), Chinese Academy of Sciences, Changchun. The results showed that the daily mean concentrations of SO₂ and NO_x were (25.0±21.6) μg/m3 (2.3-131.0 μg/m3) and(54.4±34.0) μg/m3 (17.6-183.7 μg/m3), respectively. The maximum 8-hour average O₃ concentration was(85.0±26.2) μg/m3 (31.0-173.3 μg/m3). The levels of SO₂ and NO_x were in attainment of the Class Ⅱ Ambient Air Quality Standard (GB 3095-2012). However, the O₃ concentration exceeded the corresponding standard. During the heating season, the diurnal variation of SO₂ concentration showed two peaks occurring at 06:00 and 20:00, while during the non-heating season SO₂ concentration had one peak occurring at 08:00. Similar patterns were seen in NO_x concentration, with double peaks during heating season and one peak in non-heating season. In contrast, O₃ showed only one peak in both seasons, occurring between 13:00 to 15:00. Analysis of meteorology data using the HYSPLIT back trajectory model suggested that the atmospheric pollution in Changchun was closely linked to local source emissions and meteorological conditions. Constant westerly winds were more conducive to degraded air quality, while easterly winds were more efficient to disperse accumulated air pollution.