2013年夏季典型光化学污染过程中长三角典型城市O_3来源识别

Ozone Source Apportionment at Urban Area during a Typical Photochemical Pollution Episode in the Summer of 2013 in the Yangtze River Delta

城市化、工业化、机动化的高速推进以及大气活性物质的大量排放,使得长江三角洲地区在夏秋季节面临严峻的以高浓度O3为典型特征的光化学污染问题.然而,O3与其前体物之间的高度非线性反应过程使得其来源识别变得十分复杂,因此针对高浓度O3的控制途径仍不清楚.本文以2013年7月长三角地区发生的一次持续时间长、波及范围广、强度高的高浓度O3污染过程为研究案例,基于CAMx空气质量数值模型中耦合的臭氧来源追踪方法(OSAT),采用物种示踪的方法对长三角3个代表性城市上海、苏州、杭州近地面O3的污染来源开展了模拟研究,探讨了4个源区(上海、浙北、苏南和长距离输送)、7类排放源(工业锅炉和窑炉、生产工艺过程、电厂、生活源、流动源、挥发源和天然源)对上海、苏州和杭州城区地面O3的浓度贡献.研究结果表明:长距离输送以及区域背景产生的O3约在20×10-9~40×10-9(体积分数)之间;加上上海及苏南、浙北地区排放的前体物在长三角城区地区二次生成O3,可使O3上升至40×10-9~100×10-9(体积分数)乃至更高.模拟时段内日间8 h O3浓度的地区贡献分析结果显示,长距离传输对于上海、苏州、杭州的浓度贡献分别为42.79%±10.17%、48.57%±9.97%和60.13%±7.11%;上海城区O3来源中,上海本地污染贡献平均为28.94%±8.49%,浙北地区贡献约19.83%±10.55%;苏州城区O3来源中,苏南地区贡献约26.41%±6.80%;杭州城区O3来源中,浙北地区贡献约29.56%±8.33%.从各受点日最大O3小时浓度贡献来看,长距离传输贡献比例显著下降(35.35%~58.04%),而本地污染贡献上升.区域各类污染源贡献分析结果表明,长三角地区对O3污染贡献最为突出的几类污染源分别是工业锅炉和窑炉(浓度贡献约18.4%~21.11%)、生产工艺过程(19.85%~28.46%)、流动源(21.30%~23.51%)、天然源(13.01%~17.07%)和电厂排放(7.08%~9.75%).研究结果表明,工业燃烧排放、生产工艺过程中产生的VOC排放以及流动源大气污染物排放,是造成长三角区域夏季高浓度O3的主要人为源.

With the fast development of urbanization,industrialization and mobilization,the air pollutant emissions with photochemical reactivity become more obvious,causing a severe photochemical pollution with the characteristics of high ozone concentration.However,the ozone source identification is very complicated due to the high non linearity between ozone and its precursors. Thus,ways to reduce ozone is still not clear. A high ozone pollution episode occurred during July,2013,which lasted for a long period,with large influence area and high intensity. In this paper,we selected this episode to do a case study with the application of ozone source apportionment technology( OSAT) coupled within the CAMx air quality model. In this study,4 source regions( including Shanghai,north Zhejiang,South Jiangsu and long range transport),7 source categories( including power plants,industrial process,industrial boilers and kilns,residential,mobile source,volatile source and biogenic emissions) are analyzed to study their contributions to surface O3 in Shanghai,Suzhou and Zhejiang. Results indicate that long range transport contribution to the surface ozone in the YRD is around 20 × 10-9-40 × 10-9( volume fraction). The O3 concentrations can increased to 40 × 10-9-100 × 10-9( volume fraction) due to precursors emissions in Shanghai,Jiangsu and Zhejiang. As for the regional contribution to 8 hour ozone,long range transport constitutes 42. 79% ± 10. 17%,48. 57% ± 9. 97% and 60. 13% ± 7. 11% of the surface ozone in Shanghai,Suzhou and Hangzhou,respectively. Regarding the high O3 in Shanghai,local contribution is 28. 94% ± 8. 49%,north Zhejiang constitutes 19. 83% ±10. 55%. As for surface O3 in Suzhou,the contribution from south Jiangsu is 26. 41% ± 6. 80%. Regarding the surface O3 in Hangzhou,the major regional contributor is north Zhejiang( 29. 56% ± 8. 33%). Contributions from the long range transport to the daily maximum O3 concentrations are slightly lower than those to the 8 ~ hourly O3,with the contribution of 35. 35%-58. 04%,while local contributions increase. As for the contributions from source sectors,it is found that the major source contributors include industrial boilers and kilns( 18. 4%-21. 11%),industrial process( 19. 85%-28. 46%),mobile source( 21. 30%-23. 51%),biogenic( 13. 01%-17. 07%) and power plants( 7. 08%-9. 75%). Thus,industrial combustion,industrial processes,and mobile source are major anthropogenic sources of high ozone pollution in summer in the YRD region.