Characteristics of surface ozone and nitrogen oxides at urban, suburban and rural sites in Ningbo, China
Characteristics of surface ozone and nitrogen oxides at urban, suburban and rural sites in Ningbo, China
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DOI：
10.1016/j.atmosres.2016.12.006
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发表时间：
2017-05-01
影响因子：
5.5
通讯作者：
Xiao, Hang
中科院分区：
文献类型：
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作者：
Tong, Lei;Zhang, Huiling;Xiao, Hang
地面臭氧(O-3)是一种有害的空气污染物，引起了中国越来越多的关注。本文通过对宁波市城区、郊区和农村三个不同地点臭氧和氮氧化物(NOx)混合比的连续测量，探讨了臭氧的时空特征及其与环境变量的关系。O-3的日变化以下午最大值(年平均38.7-53.1 ppb)和清晨最小值(11.7-26.2 ppb)为特征。O-3在春季(4月或5月)和秋季(10月)出现两个季节高峰，冬季(12月)出现最低值。NO水平的变化与O-3的变化趋势相反，日最大值和季节最大值分别出现在早晚高峰和冬季。在大气污染物的年际变化方面，从2012年到2015年，城区和郊区的NO和O-3水平分别呈现总体下降和上升的趋势。O-3水平与温度呈正相关，与相对湿度、NO水平呈负相关。不同风速和风向下，O-3浓度有显著差异(p<；0.001)。O-3浓度随风速变化呈非线性变化，在4m/S范围内呈增加趋势，海风的O-3掺混比较高，表明沿海气团可能携带较多的O-3。从工作日到周末，三个站点的O-3水平都有下降的趋势。在空间变化方面，郊区和农村地区的O-3水平较高，在这些地点，没有滴定消耗的O-3较少。相反，由于交通排放的影响，城市场地的O-3水平较低，但NOx水平较高。郊区的O-3日变化和月变化幅度均大于城市和农村站点。总的来说，非城市站点的O-3水平受背景输送的影响较大，而本地和区域的贡献都对城市O-3的变化起到了作用。宁波市的年均O-3混合比(22.7-37.7 ppb)与世界其他地区基本相似。然而，在温暖的季节，O-3的空气质量经常超过建议的标准，这可能会对当地人口和植物生长构成潜在威胁。(C)2016爱思唯尔B.V.保留所有权利。
Surface ozone (O-3) is a harmful air pollutant that has attracted growing concern in China. In this study, the mixing ratios of O-3 and nitrogen oxides (NOx) at three different sites (urban, suburban and rural) of Ningbo were continuously measured to investigate the spatiotemporal characteristics of O-3 and its relationships with environmental variables. The diurnal O-3 variations were characterized by afternoon maxima (38.7-53.1 ppb on annual average) and early morning minima (11.7-26.2 ppb) at all the three sites. Two seasonal peaks of O-3 were observed in spring (April or May) and autumn (October) with minima being observed in winter (December). NO levels showed generally opposite variations to that of O-3 with diurnal and seasonal maxima occurring in morning/evening rush-hours and in winter, respectively. As to the inter-annual variations of air pollutants, generally decreasing and increasing trends were observed in NO and O-3 levels, respectively, from 2012 to 2015 at both urban and suburban sites. O-3 levels were positively correlated with temperature but negatively correlated with relative humidity and NO levels. Significant differences in O-3 levels were observed for different wind speeds and wind directions (p < 0.001). O-3 levels varied non-linearly with wind speed ranges with an increasing trend within 4 m/s. Higher mixing ratio of O-3 was observed for wind blowing from the sea, which indicates that the coastal air mass might carry more O-3. A decreasing trend in O-3 levels was observed from weekdays to weekends at all the three sites. As to the spatial variation, higher levels of O-3 were observed at the suburban and rural sites where less O-3 was depleted by NO titration. In contrast, the urban site exhibited lower O-3 but higher NOx levels due to the influence of traffic emissions. Larger amplitudes of diurnal and monthly O-3 variations were observed at the suburban site than those at the urban and rural sites. In general, the O-3 levels at the non-urban sites were more affected by the background transport, while both the local and regional contributions played roles in urban O-3 variations. The annual average O-3 mixing ratios (22.7-37.7 ppb) in Ningbo were generally similar to those of other regions around the world. However, the recommended air quality standards for O-3 were often exceeded during warm seasons, which could be a potential threat to both local population and plant growth. (C) 2016 Elsevier B.V. All rights reserved.