南京北郊O3、NO2和SO2浓度变化及长/近距离输送的影响

利用2008年1月—2010年12月南京北郊O₃、NO₂和SO₂质量浓度连续观测资料结合后向轨迹模式,采用聚类分析对轨迹进行分类和KZ滤波器对数据组分进行分离的方法,讨论了南京北郊气体污染物(O₃、NO₂和SO₂)的质量浓度变化规律及长/近距离输送对该地区污染气体的影响.结果表明,南京北郊春末夏初(5、6月)O₃月均浓度出现最大值,12月出现最小值;NO₂在春季(3—5月)月平均浓度相对较高,8月份浓度全年最低,而SO₂浓度在6、7月出现最低值.不同季节气体污染物浓度日变化各有特点,O₃呈单峰分布,12:00—15:00出现浓度最大值;NO₂浓度高值则出现在夜间;SO₂在清晨出现最大值,另外,春秋冬季SO₂呈双峰型分布.长/近距离输送对南京北郊污染气体影响的分析表明,在西南方向的近距离输送影响下,该地区O₃浓度将会出现明显的高值;传输速度较慢的西北气流则会促使该地区形成高浓度的NO₂;长距离输送对O₃和NO₂的贡献与气团输送距离有关,说明该地区O₃和NO₂是区域性问题.另外,当在传输速度较慢的偏东气流的控制下,SO₂的浓度较高,说明SO₂的高浓度事件与偏东方向的近距离输送有关.

The variation of air pollutants and the impact of long-range transport in the northern suburb of Nanjing

The purpose of this study was to investigate the variation characteristics of the atmospheric pollutants (O₃, NO₂ and SO₂) and the impact of the long- and short- range transport in the northern suburb of Nanjing, China. By integrating the back-trajectory model (HYSPLIT_4), the cluster analysis and KZ-filter analysis, pollutant mass concentrations, the diurnal variations in different seasons and the impact of long- and short-range transport on the air pollutants from Jan. 2008 to Dec. 2010 were analyzed. The results showed that the monthly maximum value of O₃ occurred in May or June, while the lowest in December. The monthly mean levels of NO₂ were the highest from March to May, and the lowest in August. The minimum value of SO₂ occurred in June or July. The diurnal variations of O₃ in different seasons showed a clear peak in the afternoon. However, the highest levels of NO₂ and SO₂ occurred in the evening and morning, respectively. Different from O₃ and NO₂, the diurnal variation of SO₂ showed two peaks in spring, autumn and winter. Long- and short- range transport was one of the major contribution schemes of air pollutants in the northern suburb of Nanjing. The results showed that the slow southwest and northwest transport scenarios were significantly related to high O₃ and NO₂ concentrations, respectively, indicating that O₃ and NO₂ pollution were on a regional scale. However, the slow east, northeast and southeast flows were related to high SO₂ concentration, indicating the eastern industrial area was the main factor which impacted the SO₂ concentration at this site.