西安市可吸入颗粒物污染水平及其与气象条件的关系

Mass Concentration of PM_(10) and Its Relationship with Meteorological Conditions over Xi'an

分析了2001～2004年西安大气可吸入颗粒物(PM10)浓度的变化特征.结果显示,PM10浓度变化有明显的季节特征,冬季最高,春季次之,夏季最低,年平均浓度约为142μg/m3,明显高于同时期广州的浓度(107μg/m3).近5年的数据分析显示,PM10质量浓度总体呈下降趋势.西安地区PM10浓度与气象因素的分析显示,PM10浓度与湿度正相关,即浓度较高时,湿度相对较高,浓度较低时湿度相对也较低.PM10浓度还与风速和气压负相关.高浓度日的5d后项气团轨迹分析显示,影响西安地区的气团有A,B,C,D4条路径,其中路径B和C分别占到高浓度日的40%和45%,为主要传输路径.

The variation of PM10 mass concentration in Xi'an was investigated.The results showed that the mean mass concentration of PM10 in Xi'an 2004 was 142 μg/m3.The monthly PM10 concentration was at a low level in summer and autumn periods while at a high level in spring and winter periods.The last 5 years' data showed that the PM10 concentration in Xi'an declined slowly year by year.The relationship between PM10 concentration and meteorological factors were also studied.In most conditions,the PM10 concentration increased with the relative humidity,while the wind speed and the ambient pressure declined.The five-day air mass back trajectories were also used to analyze transport pathways of the air pollution in Xi'an.The general four trajectories which were involved in high PM10 concentration in Xi'an were identified,and trajectory A and trajectory B were main pathways,accounting for 40% and 45% of all trajectories for the high pollution days.