南京冬季典型霾天气过程多元对比分析

选取2017～2020南京地区冬季3个典型霾天气过程,综合分析了霾天气过程中污染物、气象要素以及边界层条件等影响机制与特征变化.结果表明,3次过程中,AQI指数峰值分别为304(严重污染)、227(重度污染)与176(中度污染),且与PM2.5、PM10浓度变化基本趋于一致,PM25与PM10比值基本都大于0.7;污染...

Multivariate comparative analysis of typical haze weather episodes in Nanjing

This paper selects three typical haze weather processes occured in Nanjing during winter of 2017~2020. A comprehensive analysis with the influence mechanism and characteristic changes of pollutants, meteorological elements, and boundary layer conditions in the haze pollution process are investigated. The results show that the peak values of the air quality index(AQI) values were found during the three pollution processes with 304(severe pollution), 227(severe pollution), and 176(moderate pollution).These were consistent and associated well with the changes of PM_2.5 and PM₁₀ concentrations. The ratio of PM_2.5 to PM₁₀ was greater than 0.7 signifies the dominant presence of fine aerosols in the winter period at Nanjing. During the pollution episode, the relative humidity(RH) was found maximum with greater than 70%, and the minimum wind speed was about 1 m/s. The high RH, low temperatures, and calm with stable winds provided favorable meteorological conditions for the occurrence of haze weather in the winter. During the three pollution processes, the mixing layer height observed low. During the first and second processes, the lowest height of mixing layers was only 34 m and 70 m, and the third time was 204 m. On the whole, the high value of PM_2.5 concentration corresponds to the low mixing layer height. Combined with the temperature inversion, it inhibits the vertical diffusion of pollutants and forms accumulation, resulting in increase of pollution. In Nanjing, aerosol sources were mainly from sand dust and polluted sand dust, accompanied by some continental pollution sources such as small amount of smoke, dust, and marine clean air. The analysis of backward trajectory and potential source shows that the haze pollution weather during winter in Nanjing was mainly affected by regional pollution, and the long-distance transportation of airmass from the northwest.