用激光解吸附电离飞行时间质谱法检测悬浮土壤颗粒物

在自行研制的气溶胶飞行时间激光质谱仪(ATOFLMS)上实时探测单个悬浮土壤颗粒的粒径和化学成分。利用双束连续激光对单个粒子的空气动力学粒径进行测量，并用266 nm的Nd∶YAG激光器对气溶胶单粒子进行解吸附电离作用，产物离子通过飞行时间质谱仪的无场漂移区后完成单粒子化学成分的检测。本实验中使用了4个不同地区的土壤样本，在实验室内对分析的样本进行预处理和再悬浮，通过导管引入ATOFLMS进行测量，得到大量单粒子的粒径和质谱数据。发现在众多的单粒子的阳离子质谱中，金属成分以地壳元素(Fe, K, Al, Ca)为主，在其他阳离子质谱中包含了Mg和Na等。对悬浮土壤粒子的粒径进行实时检测的结果表明这些粒子多以粗粒子为主, 粒径主要集中在1～2 μm。实验结果表明该仪器在大气气溶胶环境监测及相关研究领域具有重要的实用价值。

Single Particle Measurement of Suspended Soil Dust Using Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Real-time measurement of size and composition of single soil dust particles using an aerosol time-of-flight laser mass spectrometry (ATOFLMS) was designed in our lab.Each particle’s aerodynamic diameter was determined by measuring the delay time between two continuous-wave lasers, a Nd∶YAG laser with a 266 nm pulsed output was used to desorb and ionize aerosol particles, and ions formed in the laser desorption/ionization process were accelerated into the time-of-flight drift region where they separated by mass-to-charge ratio, Then the composition of single particle was obtained.In the present paper, soil samples were collected from four different areas in China.After the pretreatment and suspension, the particle sample was then transferred to ATOFLMS through a plastic transfer line.During the campaign, a large number of size and mass spectra of single particles were obtained.The presence of crustal elements was observed in the mass spectra of individual particles.Iron, potassium, aluminum and calcium constitute the two most commonly detected cations.Other common cations observed in the mass spectra of soil particles include magnesium, and sodium.The detection results exhibit that the coarse particles with size of 1-2 μm are dominate in the detected particles.Experimental results show the ATOFLMS have important practical value for researching and monitoring of atmospheric aerosol environment.