兰州市区臭氧时空分布特征及气象和环境因子对臭氧的影响

Temporal and Spatial Distribution of Ozone and Effects of Meteorological and Environmental Factors on Ozone in the Urban Areas of Lanzhou City

s利用2014~2016年兰州市4个监测点O_3、NO_2和CO浓度实时监测数据和日平均气温、相对湿度、气压和风速气象观测数据,统计分析了近3年O_3的时空分布特征以及环境因子(NO_2和CO)和气象因子对兰州市区O_3浓度的影响。结果表明:兰州市区O_3浓度年变化特征呈倒U型结构,夏季最高,峰值出现在5月,为(65.6±16.9)μg/m^3。4个监测点中生物制品所的年平均浓度最高。O_3的日变化为单峰分布,午后浓度较高,兰炼宾馆监测点峰值出现时间比其他区域超前约2 h。NO_2和CO与O_3的年变化相反,均表现出U型结构的年变化特征,都在12月达到峰值,分别为(2.53±0.80)mg/m^3,(78.9±28.2)μg/m^3。而NO_2和CO浓度白天浓度高于夜间。O_3浓度都随着NO_2和CO浓度的增加呈现指数形式下降。兰州市高温低湿气象条件有利于O_3的前体物(NO_2和CO)转化形成O_3。兰州市区发生高浓度O_3的气象和环境条件主要为日均气温高于20℃,相对湿度位于40%~50%以及风速≤5 m/s;NO_2浓度低于20μg/m^3,CO浓度低于0.5 mg/m^3。

In this paper,on the basis of the real-time monitoring data of O 3,NO 2 and CO concentrations at 4 automatic air monitoring points in the urban areas of Lanzhou City and the meteorological data such as daily average temperature,relative humidity,atmospheric pressure and wind speed from 2014 to 2016,the spatial-temporal distribution characteristics of O 3 and the impacts of the environmental factors(NO 2 and CO)and meteorological factors on O 3 concentration in the past three years were statistically analyzed.The results showed that the annual variation of O 3 concentration appeared U-shaped distribution in the urban areas of Lanzhou City.O 3 concentration was the highest in summer with the peak of(65.6±16.9)μg/m 3 in May.The annual average concentration at the biological products institute among the four monitoring points was the highest.The daily variation of O 3 appeared a single-peak distribution.That was,O 3 concentration turned higher in the afternoon.The peak time at Lanlian Hotel was about 2 hours ahead of the other monitoring points.Contrary to O 3,annual variation characteristics of NO 2 and CO concentrations showed an inverted U-shaped structure with both the peaks of(2.53±0.80)mg/m 3 and(78.9±28.2)μg/m 3 respectively in December.NO 2 and CO concentrations in the day time were much higher than those at night.O 3 concentration was exponentially suppressed with the increase of NO 2 and CO concentrations.High temperature and low humidity were favorable for the formation of O 3 from its precursors(NO 2 and CO).The meteorological and environmental conditions for highly-concentrated O 3 occurrence in the urban areas of Lanzhou were the daily average temperature over 20°C,relative humidity about 40%~50%,wind speed no more than 5 m/s,NO 2 concentration below 20μg/m 3,and CO concentration lower than 0.5 mg/m 3 respectively.