2009年秋季南京地区一次持续性灰霾天气过程研究

2009年10月14—27日,南京地区发生了一次持续性的灰霾天气过程。利用气象观测资料和污染物浓度监测资料,结合焚烧点监测、后向气流轨迹模拟,分析了颗粒物和气态污染物的浓度演变特征、气象要素特征及产生持续灰霾天气的可能原因。研究表明,该次过程中绝大部分时间能见度低于10 km,空气污染指数最大时达到195。地面PM2.5质量浓度有显著增长,在26日达到最大值为0.782 mg/m3。NO2质量浓度日均值在24日和27日超过了环境空气质量二级标准,其含量分别为0.094和0.099 mg/m3,对应NOx质量浓度分别为0.105和0.108 mg/m3。SO2质量浓度在22日达到峰值,最大值为0.161 mg/m3,平均值为0.083 mg/m3,低于环境空气质量二级标准。分析显示:近半个月内南京地区天气形势稳定,处于持续温度偏高、干燥无雨的状态,非常有利于灰霾天气的发生。卫星监测发现24、25、26日江淮之间中部均有火点,其中24日有50个着火点,25日增加为85个,26日减少为38个,表明有秸秆焚烧现象存在。从后向气流轨迹分析来看,在秸秆焚烧最为严重的3 d内,南京地区主要受到来自东到东北方向气流的影响,有利于秸秆焚烧形成的污染物经气流输送影响南京,造成严重灰霾天气。

Study on a continuous haze weather event during autumn of 2009 in Nanjing

A continuous haze weather event occurred in Nanjing from 14 to 27 October, 2009. Gaseous air pollutants and particulate matter were measured in order to investigate the variation of gas pollutants. Meteorological data, fire spot data as well as backward trajectory analysis were used to identify the cause of the haze weather event. Investigations showed that the visibility was less than 10km during most time of the event. The maximum of air pollution index (API) was 195, and there was a significant increasing in surface PM_2.5 concentration with the maximum of 0.782 mg/m³ on October 26. Daily concentrations of NO₂ exceeded the ambient air quality standards on October 24 and 27 with the value of 0.094 and 0.099 mg/m³. NO_x were 0.105 and 0.108 mg/m³ respectively during the two days. SO₂ concentration was 0.083 mg/m³ with the maximum of 0.161 mg/m³, which was lower compared to the ambient air quality standard. Furthermore, the atmosphere was more stable in Nanjing, the weather was continuous dry and temperature was higher during half a month. Satellite monitoring data showed that there were 50, 85, 38 fire burning points on October 24, 25, and 26, respectively, suggesting the influence of biomass burning on the occurrence of event. Backward trajectory analysis indicated that the air mass mainly originated from east and northeast, which passed through the region with the air pollutants from biomass burning, leading to the heavy haze in the last several days.