西安沙尘天气特征及其对空气质量的影响

Characteristics of Sand-Dust Events and Their Influence on Air Quality of Xi'an City

利用1971-2003年西安市常规气象观测资料、2001-2003年西安市区主要污染物日均浓度资料和2002年3月一次重度污染事件逐时的PM10浓度资料,分析了西安市沙尘天气的时间分布特征及其对主要空气污染物浓度的影响.结果表明:西安市沙尘天气近30多年来总体呈波动式明显减少的趋势,但2001-2002年有所增多,2003年又减少.沙尘天气主要出现在春季,4月最多,占全年天数的22.6%.沙尘天气对西安空气质量影响显著,可使3～4月PM10月浓度平均提高12.1%,在分析的一次强沙尘暴个例中,一小时内PM10浓度最高增加了0.585 mg·m-3, 达到0.970 mg·m-3, 从而造成严重的空气污染事件.

Based on the data of Xi＇an Meteorological Observing Station from 1971 to 2003 and the data from the Environmental Monitoring Station including daily average concentration of SO2, NO2 and PM10 from 2001 to 2003 and hourly PM10 concentration in a heavy pollution case occurred on March, 2002 in Xi＇an city, the temporal distribution characteristics of sand-dust events and their influence on air quality of Xi＇an City were analyzed. The results are as follows： In Xi＇an City, sand-dust events had a tendency of decrease in the past more than 30 years, but it increased obviously from 2000 to 2002. Most of sand-dust events mainly took place in spring especially in April, mean occurrence days in April accounted for 22.6 % of all sand-dust days of a year. The influence of sand-dust events on air quality of Xi＇an City is remarkable. Server sand-dust events could lead to heavy air pollution in Xi＇an City. They could make the average growth rate of PM10 concentration to reach 12.1% during March and April. During the case of server sand-dust storm, hourly PM10 concentration could increase by 0. 585 mg·m^-3, maximum PM10 concentration reach 0.970 mg·m^-3. Server sand-dust storm usually cause heavy air pollution event in Xi＇an City.