西安市高陵区重污染天气大气颗粒物输送路径及潜在源分析

Analysis of Atmospheric Particulate Matter Transport Paths and Potential Source Areas in Heavy Pollution Weather in Gaoling District of Xi’an City

基于2018-2021年空气质量监测数据、常规气象观测数据,对西安市高陵区大气污染特征进行分析,并利用HYSPLIT后向轨迹模式、聚类分析法、潜在源贡献分析法和浓度权重分析法,对高陵区不同天气形势下重污染天气的PM_(2.5)主要传输路径、轨迹污染特征及其潜在源区分布和贡献开展研究。结果表明:(1)2018-2021年高陵区空气污染以轻度污染为主,约占污染天气的65.4%。重污染天气主要出现在11月-次年2月,整体上重污染日数呈现下降趋势。(2)近4年重污染期间首要污染物为PM_(2.5)的天数为86天,占比高达87.8%。重污染期间PM_(2.5)平均质量浓度为201.5μg/m^(3),高出二级标准浓度1.5倍以上。(3)首要污染物为PM_(2.5)的重污染过程期间,地面气压形势场主要分为4类:高压控制型出现的重污染天数最多,占比50.0%;其次为均压场型的,出现次数占比29.0%;低压倒槽型出现次数占比16.3%;高压后部型出现次数最少,占比4.7%。其中,低压倒槽型重污染期间PM_(2.5)质量浓度均值最高,为225.0μg/m^(3)。(4)后向气流轨迹聚类分析结果表明,西北方向的远距离传输和高空传输对高陵区PM_(2.5)的质量浓度影响较小,而中短距离传输和低层传输对高陵区PM_(2.5)浓度影响较大。来自西安市区和高陵区周边城市(咸阳、渭南、铜川三市)的短距离输送及河南西部的中长距离输送占比较大,临近人口密集区域的短距离输送是影响高陵区PM_(2.5)污染的主要因素。

In this paper,based on the air quality monitoring data and conventional meteorological data from 2018 to 2021.The characteristics of air pollution in Gaoling District of Xi’an are analyzed.Moreover,the HYSPLIT backward trajectory model,cluster analysis method,potential source contribution function(PSCF)method as well as the concentration weight analysis method are used to probe the characteristics of the major PM_(2.5) transport paths,trajectory pollution characteristics and potential source area distribution and contribution of PM_(2.5) in Gaoling District under different weather conditions.The results showed that:(1)During 20182021,the air pollution in Gaoling was mainly light pollution,accounting for about 65.4%of all pollution weather.Heavy pollution events occurred mainly from November to the next February,and the number of heavy pollution days showed a downward trend generally.(2)During the heavy pollution period in the four years,the number of the days with PM_(2.5) as the primary pollutant was 86 days,accounting for 87.8%of the total days of heavy pollution.During the heavy pollution period,the average mass concentration of PM_(2.5) was 201.5μg/m^(3),exceeding the daily average secondary standard concentration limit of“Environmental Air Quality Standard”by more than 1.5 times.(3)During heavy pollution processes with PM_(2.5) as the primary pollutant,the surface pressure field situation can be divided into four categories mainly:high-pressure controlled type,with the most days of heavy pollution,accounting for 50.0%;uniform-pressure field type,with the occurrence frequency accounting for 29.0%;the low-pressure inverted trough type,with the occurrence frequency accounting for 16.3%,and the average PM_(2.5) mass concentration of this type was the highest,being 225.0μg/m^(3);and finally high-pressure posterior type,with the least occurrence percentage,only 4.7%.(4)The cluster analysis results of the backward airflow trajectory show that the long-distance transport and high-altitude transport in the northwest direction have lower effect on the PM_(2.5) mass concentration of Gaoling District,while the medium and short-distance transport and low-level transport have a higher impact.Short-distance transport from Xi’an urban area and the surrounding cities of Gaoling(Xianyang,Weinan,and Tongchuan)and medium and long-distance transport in western Henan account for a larger proportion.Short-distance transport near densely populated areas is the main factor affecting the PM_(2.5) pollution in Gaoling District.