南京市一次大气污染事件时空演化特征及影响因素

利用数理统计和后向轨迹方法,分析江苏省南京市2015年全年空气质量指数(AQI)及1月21—27日各污染指标数据,探讨南京市大气污染时空分布特征及影响因素.研究发现:2015年南京市AQI达到污染程度的天数在瑞金路、迈皋桥最多,在玄武湖最少;AQI值在秋、冬季较高,春、夏季较低,推测南京市AQI主要受不同功能区污染排放和不同季节天气变化控制.在1月21—27日大气污染事件中, AQI在仙林大学城最高,为211.094;玄武湖最低,为168.881. PM_(10)平均浓度在奥体中心最大,为229.472,玄武湖最小,为179.932. PM_(2.5)的空间分布情况与PM_(10)类似, SO_2, NO_2和O_3浓度空间差别不大.在此期间, AQI总体呈波动上升趋势, 21日、24日、26日出现3次高峰, 25日和27日下降. PM_(10)、PM_(2.5)、NO_2浓度变化趋势与AQI呈正相关关系, O_3与AQI呈负相关关系.因此,南京市大气污染在空间上具有明显区域特征,在时间上具有累加特征,同时还受周末效应和天气作用影响;主要污染物为汽车尾气、燃煤燃气和工业废气.气团后向轨迹显示,大气污染源主要来自局地和西北地区, 25日气团方向改变,导致污染物浓度下降,推测南京市大气污染受气团带来的外地污染物及天气变化的综合影响.

Temporal and Spatial Evolution Characteristics and Influencing Factors of One Air Pollution Event in Nanjing

The air quality index (AQI) in 2015 and the data of the pollutant index on January 21st to 27th were analyzed by the means of mathematical statistics and backward trajectory to study the time and spatial characteristics and influencing factors of atmospheric pollution in Nanjing. It is revealed that in 2015, the number of the days that AQI index reached the degree of pollution is the most at Ruijin Rode site and Maigao bridge site, while it is the least at Xuanwu Lake site; AQI index is high in autumn and winter, and it is low in spring and summer. It is inferred that AQI index in Nanjing is mainly determined by area pollution discharge at different functional area and weather changes in different seasons. In the air pollution event from January 21st to January 27th, AQI index is the highest at Xianlin campus which is 211.094; AQI is the lowest at Xuanwu Lake which is 168.881. The average concentration of PM10 at Aoti centre is the highest which is 229.472, it is the lowest at Xuanwu Lake which is 179.932. The dimensional distributing feature of PM2.5 is the same as that of PM10. The spatial distribution of concentration of SO2, NO2 and O3 has no much difference. During the event, the general trend of AQI index is on the fluctuating rise, it appears 3 peak values on 21st, 24th and 26th, and it declines on 25th and 27th. The changing trend of concentration of PM10, PM2.5, NO2 is related to the AQI, while the changing trend of concentration of O3 is negative to AQI. Therefore, the air pollution in Nanjing has obvious regional characteristics in space and cumulative feature in time, and it is affected by weekend effect and the influence of weather. The pollution is automobile exhaust emission, coal-burning and waste gas emission. The back trajectories of pollution show that air pollution is mainly from Nanjing and north-west China. The changing of wind direction of air on 25th resulted in the level of the pollution dropping, so refer that air pollution is comprehensively affected by air pollution in air mass from other places and weather change.