Aerosol mass spectrometry: particle-vaporizer interactions and their consequences for the measurements
Aerosol mass spectrometry: particle-vaporizer interactions and their consequences for the measurements
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DOI：
10.5194/amt-8-3811-2015
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发表时间：
2015-01-01
影响因子：
3.8
通讯作者：
Borrmann, S.
中科院分区：
文献类型：
--
作者：
Drewnick, F.;Diesch, J. -M.;Borrmann, S.
Aerodyne气溶胶质谱仪（AMS）是一种常用的在线测量环境亚微米气溶胶成分的仪器。借助对闪蒸和电子碰撞电离过程的校准和一些假设，该仪器提供了关于各种非耐火环境气溶胶组分的可靠定量信息。然而，当测量接近某些人为或海洋来源的半难处理气溶胶时，如果不仔细分析独特的离子，同位素模式，和潜在的缓慢汽化，在这里，我们讨论了与AMS钨蒸发器的气溶胶粒子的相互作用的各个方面，测量结果：半耐火组分-即，在蒸发器和电离器温度下蒸发但不闪蒸的组分，如金属卤化物（例如，Al、Ba、Cd、Cu、Fe、Hg、K、Na、Pb、Sr、Zn的氯化物、溴化物或碘化物）-可以半定量地测量，尽管它们从蒸发器中的蒸发相对较慢。即使非耐火部件（例如，NH 4 NO3或（NH 4/2SO 4）快速蒸发，在某些条件下，它们在蒸发动力学上的差异可能导致阈值测量中离子收集效率的不期望的偏差。与来自气溶胶流的氧气的化学反应可对某些组分的质谱产生影响（例如，有机物种）。最后，气溶胶与汽化器表面的化学反应可导致质谱中的额外信号（例如，WO 2Cl 2-相关的信号从微粒Cl）和在空调或污染的蒸发器，与潜在的记忆效应影响质谱的后续measurements.Laboratory实验室调查这些粒子蒸发器的相互作用，并与现场结果一起讨论，表明典型的大陆或城市气溶胶的测量没有显着的影响，而在实验室、靠近人为来源或海洋环境中对半难熔气溶胶的测量可能会因这些影响而产生偏差。
The Aerodyne aerosol mass spectrometer (AMS) is a frequently used instrument for on-line measurement of the ambient sub-micron aerosol composition. With the help of calibrations and a number of assumptions on the flash vaporization and electron impact ionization processes, this instrument provides robust quantitative information on various non-refractory ambient aerosol components. However, when measuring close to certain anthropogenic or marine sources of semi-refractory aerosols, several of these assumptions may not be met and measurement results might easily be incorrectly interpreted if not carefully analyzed for unique ions, isotope patterns, and potential slow vaporization associated with semi-refractory species.Here we discuss various aspects of the interaction of aerosol particles with the AMS tungsten vaporizer and the consequences for the measurement results: semi-refractory components -i.e., components that vaporize but do not flash-vaporize at the vaporizer and ionizer temperatures, like metal halides (e.g., chlorides, bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg, K, Na, Pb, Sr, Zn) - can be measured semi-quantitatively despite their relatively slow vaporization from the vaporizer. Even though non-refractory components (e.g., NH4NO3 or (NH4/2SO4) vaporize quickly, under certain conditions their differences in vaporization kinetics can result in undesired biases in ion collection efficiency in thresholded measurements. Chemical reactions with oxygen from the aerosol flow can have an influence on the mass spectra for certain components (e.g., organic species). Finally, chemical reactions of the aerosol with the vaporizer surface can result in additional signals in the mass spectra (e.g., WO2Cl2-related signals from particulate Cl) and in conditioning or contamination of the vaporizer, with potential memory effects influencing the mass spectra of subsequent measurements.Laboratory experiments that investigate these particle-vaporizer interactions are presented and are discussed together with field results, showing that measurements of typical continental or urban aerosols are not significantly affected, while measurements of semi-refractory aerosol in the laboratory, close to anthropogenic sources or in marine environments, can be biased by these effects.