西安采暖期PM_(2.5)及其水溶性无机离子的时段分布特征

Time series characteristics of atmospheric particulate pollution PM_(2.5) and its water-soluble inorganic ion during the heating period of Xi'an

为了探讨西安市采暖期大气颗粒物PM2.5及其水溶性无机成分的污染水平,于2010年1月4日—2月1日按一天8个时段(每个时段3 h)连续采集PM2.5样品四周,每周更换一次滤膜。结果显示,西安市采暖期PM2.5的质量浓度时段差异较大,呈现明显的双峰分布特征:21:00—24:00时段(147.516μg/m3)和09:00—12:00时段(141.678μg/m3)。4种被测水溶性无机组分总浓度为39.801μg/m3,占PM2.5总浓度的30.5%。SO24-和NO3-是最主要组分,占到4种无机组分的86.2%。各离子间相关分析显示,Cl-只与NO3-有较强的相关性,表明机动车尾气对Cl-有较大的贡献。SO24-和NO3-时段分布规律较为相似,与PM2.5浓度的时段分布特征相反:在PM2.5污染最轻的15:00—18:00时段,SO24-和NO3-的相对含量达到一天中的最高浓度时段,而在PM2.5双峰时段,它们的含量有所降低。

In order to investigate the pollution levels of atmospheric particles PM2.5 and its water-soluble components in the heating period of Xi＇an,PM2.5 were collected eight times at three-hour intervals everyday and filter was changed each week,a total of four contiguous weeks from Jan 4th to Feb 1st of 2010.The results showed that the mass concentration of PM2.5 was quite different in different times,and that obvious bimodal distribution emerged： 21：00—24：00（147.516 μg/m3） and 09：00—12：00（141.678 μg/m3）.The concentration of the four water-soluble components was 39.801 μg/m3,and accounted for 30.5% of the total PM2.5.SO2-4 and NO-3 were the main components,and accounted for 86.2% of four inorganic components.The ions correlation analysis revealed that Cl-only had a strong correlation with NO-3,which meant that the motor vehicle exhaust had a greater contribution for Cl-.SO2-4 and NO-3 had similar time distribution,and their relative concentration in PM2.5 had the opposite time distribution pattern with PM2.5,which achieved the highest levels in the 15：00—18：00 period while the concentration of PM2.5 was lowest,and decreased when PM2.5 increased.