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251.
Francois‐Xavier d'Abzac Andrew D. Czaja Brian L. Beard James J. Schauer Clark M. Johnson 《Geostandards and Geoanalytical Research》2014,38(3):293-309
The influence of ablation cell geometry (Frames single‐ and HelEx two‐volume cells) and laser wavelength (198 and 266 nm) on aerosols produced by femtosecond laser ablation (fs‐LA) were evaluated. Morphologies, iron mass distribution (IMD) and 56Fe/54Fe ratios of particles generated from magnetite, pyrite, haematite and siderite were studied. The following two morphologies were identified: spherules (10–200 nm) and agglomerates (5–10 nm). Similarity in IMD and ablation rate at 198 and 266 nm indicates similar ablation mechanisms. 56Fe/54Fe ratios increased with aerodynamic particle size as a result of kinetic fractionation during laser plasma plume expansion, cooling and aerosol condensation. The HelEx cell produces smaller particles with a larger range of 56Fe/54Fe ratios (1.85‰) than particles from the Frames cell (1.16‰), but the bulk aerosol matches the bulk substrate for both cells, demonstrating stoichiometric fs‐LA sampling. IMD differences are the result of faster wash out of the HelEx cell allowing less time for agglomeration of small, low‐δ 56Fe particles with larger, high‐δ 56Fe particles in the cell. Even with a shorter ablation time, half the total Fe ion intensity, and half the ablation volume, the HelEx cell produced Fe isotope determinations for magnetite that were as precise as the Frames cell, even when the latter included an aerosol‐homogenising mixing chamber. The HelEx cell delivered a more constant stream of small particles to the ICP, producing a more stable Fe ion signal (0.7% vs. 1.5% RSE for 56Fe in a forty‐cycle single analysis), constant instrumental mass bias and thus a more precise measurement. 相似文献
252.
Based on meteorological and pollution data from January 2017 to December 2019, in this paper the long-term distribution of surface aerosol particles, and the interaction between aerosol pollution and meteorological factors in four cities of the Yangtze River Delta (YRD) region is investigated. The long-term observation shows the law of typical aerosol pollution characteristics. Meteorological factors are significantly different during aerosol-polluted and nonpolluted days. The effect of each meteorological factor on aerosol pollution may vary by different seasons and cities. The changes in meteorological factors are not completely consistent during aerosol fine-mode and coarse-mode polluted days. To distinguish the possible sources of surface aerosol particles, the potential source contribution function and concentration-weighted trajectory models are applied to study transport sources. Based on the detailed analyses, this study will provide a reliable basis for further pollution control in the YRD. 相似文献