摘要：2010年4月在西安市区4个点使用低流量采样器同步连续采集2周 (24 h/d) 细颗粒物PM_2.5和可吸入颗粒物PM₁₀样品, 分别利用热光碳分析仪、离子色谱和X射线荧光光谱仪分析其含碳组分 (有机碳和元素碳) 、水溶性无机离子 (NH₄⁺、Na⁺、K⁺、Ca²⁺、Mg²⁺、F^-、Cl^-、SO₄^2-、NO₃^-) 和元素Ca、Fe等浓度。结果表明, 沙尘暴期间, PM₁₀的质量浓度是PM_2.5的3倍, PM2.5和PM10中有机碳浓度大于正常天气的, SO₄²--NO₃^--NH₄⁺浓度急剧减小, 明显小于正常天气, 这与干燥沙尘暴的稀释作用有关;后向轨迹、气溶胶指数和Ca与Fe元素质量浓度比验证了沙尘暴颗粒来源西部戈壁沙尘和黄土高原;阴阳离子平衡计算显示沙尘事件颗粒物呈碱性, 阴阳离子差异估算的CO₃^2-含量与Ca²⁺具有强相关性, 表明沙尘暴颗粒以CaCO₃为主。

关键词：细颗粒物 (PM _2.5) ；可吸入颗粒物 (PM₁₀) ；沙尘暴

Abstract：To evaluate the chemical profiles and sources of spring aerosol over Xi'an, 24 h a day fine particulate matter PM_2.5 and inhalable particulate matter PM₁₀ samples were collected at 4 urban sites simultaneously in 2 weeks using minival samplers. PM_2.5 and PM₁₀ mass concentrations, carbon analyses (organic and elemental carbon) , water inorganic ion (NH₄ ⁺, Na^+, K⁺, Ca²⁺, Mg²⁺, F^-, Cl^-, SO₄ ^2-, NO₃^-) and trace elements (Ca and Fe) were determined by gravimetry, ion chromatography, thermal-optical carbon analyzer and ED-XRF spectrometry, respectively. The results show that the average mass concentration of PM10 is 3 times larger than that of PM_2.5. Comparing with that in the non-dust period a sharp increase in organic carbon level is observed during the dust period. SO₄ ^2--NO₃^--NH₄ ⁺concentration is much higher in dust storm events than in normal days, mainly due to dilution of enhanced particulates in dry dust storm. The transport pathways and sources of PM_2.5 and PM₁₀ in dust storm period are identified on the basis of the air mass trajectories and the ratio of Ca and Fe elements. CO₃ ^2-concentration is estimated using the method of ion balance. A strong relationship is observed between evaluated CO₃ ^2-and measured Ca²⁺, which indicates that CaCO₃ is a main composition during dust storm period.

Keywords：fine particulate matter (PM_2.5) ; inhalable particulate matter (PM₁₀) ; dust storm