南京北郊夏季近地层臭氧及其前体物体积分数变化特征

Variation Characteristics of Surface Ozone and Its Precursors During Summertime in Nanjing Northern Suburb

南京北郊,钢铁、石化等重工业集中,大气污染现状不容乐观.为了研究此类重工业地区夏季光化学污染特征,于2013年5月18日~8月31日连续观测了臭氧及其前体物的浓度并同时记录了常规气象要素.结果表明,观测期间臭氧(O3)、氮氧化物(NOx)和挥发性有机物(VOCs)平均体积分数分别为(32.01±15.20)×10-9、(21.50±14.02)×10-9、(33.16±25.20)×10-9,一氧化碳(CO)为(0.66±0.44)×10-6;O3体积分数小时均值最大值达146.42×10-9;O3超过国家环境空气质量二级标准14.1%.对污染物进行浓度频率分布近似得到观测期间O3、NOx和VOCs背景体积分数分别为(5.71±2.51)×10-9、(12.20±0.36)×10-9和(22.44±0.38)×10-9,CO为(0.28±0.01)×10-6.观测点污染物受周边排放源的影响较大.在风速为2~3 m·s-1的西南风作用下,VOCs中的活性物种体积分数较高,O3体积分数容易累积达到高值;偏东风主导下主要来自周边工业源和交通源的NOx、CO和VOCs体积分数易出现高值.南京亚青期间对工业生产和部分机动车采取了调控措施,O3体积分数未明显减少,并有4 d超过国家二级标准.

It is not optimistic about current air quality in Nanjing northern suburb, an area with the agglomeration of heavy industry such as steel-making and petrochemical industry. Measurement of ozone and its precursors conducted from May 18th to August 31st , with the Meteorological data recorded simultaneously, were analyzed to characterize the local photochemical pollution in summertime. The results showed that the average volume fraction of ozone (O3 ), nitrogen oxide (NOx ) and volatile organic compounds (VOCs) in Nanjing northern suburb was about (32. 01 ± 15. 20) × 10 - 9 , (21. 50 ± 14. 02) × 10 - 9 and (33. 16 ± 25. 20) × 10 - 9 , respectively, and carbon monoxide (CO) was (0. 66 ± 0. 44) × 10 - 6 . For O3 , the maximum value reached 146. 42 × 10 - 9 , exceeding the National Ambient Air Quality Standard Ⅱ by a rate of 14. 1% . The background level of O3 , NOx , VOCs and CO were estimated to be (5. 71 ± 2. 51) × 10 - 9 , (12. 20 ± 0. 36) × 10 - 9 , (22. 44 ± 0. 38) × 10 - 9 and (0. 28 ± 0. 01) × 10 - 6 , respectively, from the frequency distribution of their hourly averaged volume fraction. Pollutants were significantly affected by local emission sources near the site. When affected by the southwest wind with the speed of 2-3 m·s - 1 , active species of VOCs were easy to reach high level, accompanied by an increased concentration of O3; Under the influence of easterly winds, NOx , CO and VOCs, mainly emitted from industrial sources and traffic sources, were prone to reach high level. The regulation and control measures were taken on industrial production and some vehicles during the Nanjing Asian Youth Games, but the concentration of O3 was not significantly reduced, and there were 4 days exceeding the National Ambient Air Quality Standard Ⅱ.