芜湖市臭氧污染特征及气象成因分析

Characteristics of Ozone Pollution and Analysis of Meteorological Causes in Wuhu City

文章基于芜湖市2019年环境空气质量监测数据及同期气象观测资料分析了芜湖市臭氧污染时空分布特征及气象成因。结果表明,2019年芜湖市由O_(3)导致污染天数占比高达54.9%,O_(3)已成为影响芜湖市环境空气质量的首要污染因子,但以轻度污染(91.1%)和中度污染(8.7%)为主,极少发生重度及以上污染(0.2%)天气。2019年各县(市)区O_(3)第90百分位浓度范围为172~196μg/m^(3),整体呈"周边高于中心"的空间分布规律,湾沚区、繁昌区和无为市的O_(3)浓度相对较高。季节上呈夏季(195μg/m^(3))>秋季(166μg/m^(3))>春季(159μg/m^(3))>冬季(85μg/m^(3))的分布规律,逐月O_(3)浓度呈"倒U型"分布,5-9月为O_(3)污染的高发时段。日变化O_(3)浓度呈典型的"单峰分布",在16:00左右达到峰值;NO、NO_2和CO浓度则呈"双峰分布",在08:00和20:00达到峰值。气温、湿度、风速、风向均是影响芜湖市O_(3)浓度的重要气象因子,O_(3)浓度与气温呈"正相关"关系,与湿度呈"负相关"关系,Pearson系数分别为0.58和-0.56。高温低湿的气象条件更加有利于O_(3)的生成与积累,当气温为25~40℃,湿度为20%~60%时,易出现O_(3)超标现象,超标率为41.0%~71.8%。当风速为2~4 m/s,主导风向为东北、偏东及西南方向时,O_(3)浓度相对较高,各地O_(3)浓度高值所在风向与前体物高排放企业分布方向呈高度一致性,东北、东部及西南方向的污染源排放对芜湖市臭氧污染影响较大。

The temporal and spatial distribution characteristics and meteorological causes of ozone pollution in Wuhu City were analyzed based on the data obtained from the air quality monitoring station and meteorological observation station.Results showed that,O_(3) has caused 54.9%of the polluted weather in 2019,and it has become the primary pollution factor affecting the environmental air quality,with light pollution(91.1%)and moderate pollution(8.7%)dominated,severe pollution(0.2%)rarely occurs.In 2019,the O_(3) concentration range in Wuhu is about 172~196μg/m^(3),showed a spatial distribution characteristic of"suburbs higher than the center".The O_(3) concentration in Wanzhi,Fanchang and Wuwei was relatively high.Seasonally,the distribution pattern was summer(195μg/m^(3))>autumn(166μg/m^(3))>spring(159μg/m^(3))>winter(85μg/m^(3)).Monthly O_(3) concentration presented an distribution characteristic of"inverted U-shaped",O_(3) pollution occured frequently from May to September.Daily variation of O_(3) concentration followed"the unimodal distribution",with the maximum value at 16:00.Hourly NO,NO2 and CO concentration followed"the bimodal distribution",with the maximum value at 08:00 and 20:00.High-temperature and low-humidity weather conditions are more conducive to the formation and accumulation of O_(3).Temperature,humidity,wind speed,and wind direction are all important meteorological factors affecting the O_(3) concentration in the City.The O_(3) concentration has a"positive correlation"relationship with temperature and a"negative correlation"relationship with humidity.The Pearson coefficients are 0.58 and-0.56,respectively.Weather conditions of high temperature and low humidity are more conducive to the generation and accumulation of O_(3).When the temperature is25℃to 40℃and the humidity is 20%~60%,O_(3) over-standard weather is prone to occur,and the over-standard rate is about41.0%to 71.8%.High O_(3) concentration is mainly concentrated when the wind speed is 2~4 m/s and the wind direction is northeast,east and southwest.The wind direction where the O_(3) concentration is high is highly consistent with the distribution direction of the companies that emit high precursors,and ozone pollution in the City is greatly affected by pollution source emissions in the northeast,east and southwest.