洞庭湖区一次重度空气污染过程成因分析

利用AQI和PM_(2. 5)质量浓度、地面气象要素、NCEP、ERSST_V3、GBL等资料,对2016年12月29日至2017年1月5日洞庭湖区一次重度空气污染过程成因进行了分析。结果表明,静稳天气形势下的累积效应和本地持续升温、降压、增湿、小风导致污染物浓度不断增加。本地风速与雨量对污染物浓度产生显著影响。降温前风速明显加大,有利于污染物快速扩散。湿度增加有利于污染物吸湿性增长,但高湿易引起降水有利于污染物的湿清除。此次重度空气污染过程中大气稳定度为中性或稳定,14:00混合层高度逐渐降低且重度空气污染日降至100 m以下。污染物空间分布与主导风向和污染通道密切相关。气流后向轨迹分析表明,洞庭湖区各地气流来源和影响路径差异明显,且存在大范围区域性同步污染现象。北方外来污染源是洞庭湖区重要的污染面源,本地工业污染排放点源和地理条件也是洞庭湖区空气污染物空间分布差异的重要因素。

Impact factors of a Heavy Air Pollution Process in Dongting Lake Area

Using AQI and PM_2.5 mass concentration, ground meteorological elements, NCEP, ERSST_V3, GBL and other materials, the causes of a severe air pollution process from December 29,6 to January 5,7 in Dongting Lake area were analyzed. The results showed that the cumulative effect of static and steady weather, and local continuous heating and lowering of pressure and humidifying and small wind led to the increasing concentrations of pollutants. Local wind speed and rainfall had a significant effect on pollutant concentration. The wind speed obviously increased before cooling that was conducive to the pollutants spread rapidly. The increase of humidity was conducive to the growth of moisture absorption, but the high humidity causes precipitation to be beneficial to the wet cleaning of pollutants. The atmospheric stability was neutral or stable during the heavy air pollution process, and the mixing layer was gradually reduced and fell below 100 m in the severe air pollution day at 14:00. The spatial distribution of pollutants was closely related to the dominant wind direction and pollution channel. The backward trajectory analysis of airflow showed that the sources of airflow and the influence path in Dongting Lake area were obvious difference. There was a large regional synchronous pollution phenomenon. The northern outside source was an important non-point source of pollution in Dongting Lake, and the local industrial pollution emission point source and geographical conditions were also important factors for the spatial distribution of air pollutants in Dongting Lake area.