【摘要】 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,PM2.5与PM10比值基本都大于0.7;污染期间,相对湿度几乎都在70%以上,最低风速均在1m/s左右,高湿的环境、稳定的气温与静小风为霾天气的发生提供了有利的气象条件;3次过程中,均有低混合层高度出现,第1、2次混合层最低高度仅为34m,70m,第3次为204m,整体上PM2.5浓度高值与低混合层高度相对应,配合高频率、强度大的逆温,抑制污染物的垂直扩散形成聚集,导致污染加剧;气溶胶来源多以沙尘与污染性沙尘为主,同时伴随着部分大陆性污染、少量烟尘与海洋清洁空气;后向轨迹与潜在源分析表明,3次冬季南京地区霾污染天气主要受区域污染影响为主,同时气流远距离输送也造成了重要影响,尤其以西北远距离输送居多.更多还原

【Abstract】 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 PM2.5 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 PM2.5 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.更多还原