石家庄市主城区臭氧污染特征及气象成因分析

为了解石家庄市主城区O₃(臭氧)污染特征及其影响因子，基于2015-2018年石家庄市空气质量连续监测资料和同期气象数据分析了主城区O₃污染总体特征及气象成因.结果表明:①石家庄市主城区大气光化学污染日益严峻，ρ(O₃)日均值由2015年的47 μg/m3增至2018年的66 μg/m3，ρ(O₃)超过GB 3095-2012《环境空气质量标准》二级标准限值的天数由2015年的20 d增至2018年的70 d.②ρ(O₃)存在明显的季节性差异，呈夏季(89±33)μg/m3] >春季(69±25)μg/m3] >秋季(40±26)μg/m3] >冬季(28±16)μg/m3]的特征；ρ(O₃)日变化呈单峰型分布，谷值出现在06:00-07:00，峰值出现在15:00-16:00，且15:00-17:00是ρ(O₃)超标的高发时段.③ρ(O₃)与气温呈指数关系，当气温为20~25、25~30、≥ 30℃时，ρ(O₃)日均值分别为75、90及119 μg/m3.ρ(O₃)在相对湿度为60%时存在拐点，当相对湿度≤ 60%时，ρ(O₃)随相对湿度的增大而上升；当相对湿度>60%时，ρ(O₃)随相对湿度的增大而下降.风速与ρ(O₃)呈分段线性关系，当风速 < 2 m/s时，ρ(O₃)随风速的增加而上升；当风速≥ 2 m/s时，ρ(O₃)随风速的增加而下降.④影响石家庄市主城区ρ(O₃)升高的污染源主要位于其东-东南-南方位，其次为东北-东方位，而西部和北部地区则较少.⑤石家庄市主城区ρ(O₃)超标多发生在气温>20℃，相对湿度介于40%~70%之间，风速在1.5~3.0 m/s之间的气象背景下，经统计，当气象条件同时符合上述三项气象要素时，ρ(O₃)超标天数占3-10月总超标天数的66.5%.研究显示，气温>20℃、相对湿度为40%~70%、风速为1.5~3.0 m/s的气象条件可初步作为石家庄市主城区O₃污染的预警指标. 

Characteristics of Ozone Pollution and Its Meteorological Factors in Shijiazhuang Urban Area

In order to analyse and understand the ozone (O₃) pollution characteristics and meteorological conditions in urban areas of Shijiazhuang and its influencing factors, the observation data from environmental monitoring sites and meteorological stations in Shijiazhuang from 2015 to 2018 were used. The results showed that: (1) O₃ pollution became worse in urban areas of Shijiazhuang, the average daily ρ(O₃) increased from 47 μg/m3 in 2015 to 66 μg/m3 in 2018, and the number of O₃ pollution days increased from 20 in 2015 to 70 in 2018; (2) ρ(O₃) showed obvious seasonal variation, i.e. summer ((89±33)μg/m3) > spring ((69±25)μg/m3) > autumn ((40±26)μg/m3) > winter ((28±16)μg/m3). The daily variation distribution of ρ(O₃) followed the unimodal distribution, with the minimum value detected at 06:00-07:00 and the maximum value detected at 15:00-16:00. (3) An exponential relationship between temperature and ρ(O₃) was observed, i.e. when the atmospheric temperature was 20-25, 25-30 and ≥ 30℃, ρ(O₃) was 75, 90 and 119 μg/m3, respectively. Significantly segmented characteristics were observed between relative humidity and ρ(O₃). When the relative humidity was ≤ 60%, ρ(O₃) increased with the increase in relative humidity. However, when the relative humidity was >60%, ρ(O₃) decreased with the increase in relative humidity. A piecewise linear relationship between temperature and ρ(O₃) was observed. When the wind speed was ≥ 2 m/s, ρ(O₃) decreased with the increase in wind speed. However, when the wind speed was < 2 m/s, ρ(O₃) increased with the increase in wind speed. (4) ρ(O₃) pollution sources in urban areas of Shijiazhuang in the east-southeast-south position were the largest, followed by the northeast-east position. Meanwhile, ρ(O₃) pollution sources in the western and northern regions were the smallest. (5) In Shijiazhuang urban area, ρ(O₃) mostly exceeded the standard when the temperature was >20℃, relative humidity was 40%-70% and wind speed was 1.5-3.0 m/s. According to the statistics, 66.5% of the total days exceeded the standard under the aforementioned meteorological conditions. The results also show that the aforementioned meteorological conditions can be used as an early warning index of O₃ pollution.