乌鲁木齐PM_(2.5)时空演变及扩散轨迹模拟

Spatio-Temporal Evolution and Diffusion Trajectory Simulation of PM_(2.5) in Urumqi City

为了解乌鲁木齐市大气颗粒物PM_(2.5)污染现状,该文基于2014-2019年乌鲁木齐空气质量监测站点PM_(2.5)小时数据与同期GADS气象数据,分别从年、月、日等时间尺度探索了乌鲁木齐市PM_(2.5)浓度时空变化特征,并利用HYSPLIT模型对PM_(2.5)扩散轨迹进行模拟分析。结果表明:(1)乌鲁木齐市PM_(2.5)年均浓度总体呈现了2016年之前上升,2017年之后下降趋势;4-9月PM_(2.5)月均浓度总体低于年均二级标准35μg/m^(3),10月-次年3月PM_(2.5)月均浓度远高于35μg/m^(3);日均值浓度也呈现先下降后上升的趋势,2015年优良率为71.6%,2017年为66.3%,2019年为73.4%。(2)PM_(2.5)浓度空间分布上呈现出西北城区高、东南城区低的变化趋势,四季变化较分明:冬季(148.9μg/m^(3))>秋季(50.9μg/m^(3))>春季(49.8μg/m^(3))>夏(28.0μg/m^(3))。(3)受地形与气象等因素的影响,PM_(2.5)扩散轨迹主要分布于尘源区附近,极少轨迹通过高空输送到达较远的地区。

To understand the current status of PM_(2.5)pollution of atmospheric particulate matter in Urumqi,this paper explores the spatial and temporal variation characteristics of PM_(2.5)concentrations in Urumqi from annual,monthly and daily time scales based on hourly PM_(2.5)data from Urumqi air quality monitoring stations from 2014-2019 and GADS meteorological data from the same period,and uses the HYSPLIT model to conduct PM_(2.5)dispersion trajectory The simulation analysis was carried out using the HYSPLIT model.The results show that(1)the annual average PM_(2.5)concentrations in Urumqi generally showed a trend of increasing before 2016 and decreasing after 2017;the monthly average PM_(2.5)concentrations from April to September were generally lower than the annual average secondary standard of 35μg/m^(3),and the monthly average PM_(2.5)concentrations from October to March were much higher than 35μg/m^(3);the daily average concentrations also showed a trend of first decreasing and then increasing,with an excellent rate of 71.6%in 2015.The excellent rate was 71.6%,66.3%in 2017 and 73.4%in 2019.(2)The spatial distribution of PM_(2.5)concentrations shows a trend of high in the northwest urban area and low in the southeast urban area,with more distinct changes in the four seasons:winter(148.9μg/m^(3))>autumn(50.9μg/m^(3))>spring(49.8μg/m^(3))>summer(28.0μg/m^(3)).(3)Due to topography and meteorological factors,PM_(2.5)dispersion trajectories are mainly distributed near the dust source area,with very few trajectories reaching more distant areas through high altitude transport.