天津市臭氧污染特征与影响因素分析

2013—2015年,天津市臭氧(O_3)浓度整体呈下降趋势,污染状况略低于京津冀区域的其他城市。O_3浓度春、夏季高,冬季低,高值主要集中在5—9月,浓度从早上06:00开始升高,至中午14:00达到峰值。污染主要集中在中心城区、西部和北部地区,东部、南部和西南部地区污染相对较轻。O_3浓度在温度303 K以上、相对湿度70%以下或西南风为主导时较高。VOCs/NOx比值低于8,O_3的生成处于VOCs控制区。芳香烃类和烯烃类对天津市O_3生成贡献最大,其中,乙烯和甲苯为O_3生成潜势贡献最大的物种,其次为间/对二甲苯、丙烯、邻二甲苯、异戊二烯、反-2-丁烯、乙苯等,通过控制汽车尾气、化工行业及溶剂使用等对O_3生成潜势贡献大的VOCs排放源可有效控制天津市O_3污染。

Characteristics of Ozone Pollution and Its Influencing Factors in Tianjin

The average annual ozone concentration in Tianjin showed a decreased trend in 2013-2015. Local ozone pollution was slightly better than the surrounding cities in Beijing-Tianjin-Hebei region. Ozone concentration was higher in spring and summer, lowest in winter, with high values from May to September. The diurnal variations showed that ozone concentration began to rise from 06:00 and then reached the peak value at 14:00. Ozone concentration also showed obvious spatial distributions, with high concentrations in the central, western and northern region and low concentrations in the eastern, southern and southwestern region. Ozone concentration was always high when the ambient temperature was higher than 303 K and the relative humidity was lower than 70%, or the winds blew from the southwest. VOC/NO_x ratios of initial concentrations were lower than 8, indicating that the ozone pollution in Tianjin is in the VOCs sensitive areas. VOCs characteristics showed that aromatics and alkenes contributed most to VOCs in Tianjin, and ethylene and methylbenzene were the most important species which contributed most to ozone formation potential. Hence, ozone pollution in Tianjin could be effectively controlled through controlling the volatilization sources of automobile emissions, industrial production and solvent use sources which contribute greatly to ozone formation potential.