西安市环境空气质量变化特征及其与气象条件的关系

Ambient air quality change and its relationship with meteorological conditions in Xi'an

采用2002—2011年大气污染物的现状监测资料以及同期气象观测资料,分析西安市空气污染的时空分布特征及其与气象条件的关系,并探讨空气质量为优及轻微污染以上的天气事件对应的高空典型环流形势,研究污染成因及污染物传输规律。结果表明:西安市污染较为严重的污染物为PM10,较大浓度值出现在冬季采暖期,雨水能对污染物起到有效的湿清除作用,且空气质量状况具有明显的延续性,天气系统具有延续性是造成空气质量延续性的可能原因;逆温的存在,最大混合层高度的降低造成大气层结稳定,风速较小,阻碍空气的对流运动,使污染物在垂直方向上的扩散能力较弱,不利于污染物扩散,易造成环境空气质量下降,引起空气污染的发生。

Based on the data of atmospheric pollutants and the corresponding meteorological observation data from 2002 to 2011 in Xi＇an, the temporal and spatial distributions of air pollution and its relationship with meteorological conditions were analyzed. The typical upper-level circulation situation in the day when air quality is superior grade or above light pollution grade, forming reasons and transport path of pollutants were discussed. The results indicate that the primary pollutant is PM10 in Xi＇an, and its maximum concentration appears in winter during heating peri- od. Rainfall is the significant wet scavenging effect for pollutants, and air quality status has obvious continuity ow- ing to the continuity of weather system. Presence of inversion temperature and decrease of the maximum mixed layer height make atmospheric stratification stable and wind speed small, hinder the convective movement of air, which lead to the weak diffusion of pollutants along the vertical direction. Thus, it is not favorable to the diffusion of pollutants, and it easily makes the ambient air quality descended.