Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
Anal Chem. 2012 Mar 6;84(5):2253-9. doi: 10.1021/ac202868h. Epub 2012 Feb 24.
The nano aerosol mass spectrometer provides a quantitative measure of the elemental composition of individual, ambient nanoparticles in the 10-30 nm size range. In this work, carbon mole fraction plots are introduced as an efficient means of visualizing the full range of particle compositions in an ambient data set. These plots are constructed by plotting the composition of each particle in the data set, beginning with the particle having the highest carbon mole fraction and ending with the particle having the lowest carbon mole fraction. The method relies on the observation that the carbon content of an ambient particle is generally anticorrelated with oxygen, nitrogen, and sulfur. Carbon mole fraction plots allow internal vs external mixing of particle compositions to be assessed, and they provide a means of exploring the relationship between the oxidation of carbonaceous matter and the presence of inorganic species in a particle. It is shown that unoxidized carbonaceous matter exists primarily as externally mixed particles, whereas oxidized carbonaceous matter is found only in particles that also contain a significant amount of inorganic species. Particles containing oxidized carbonaceous matter are generally neutralized, whereas particles containing unoxidized carbonaceous matter or no carbon at all are acidic. Carbon mole fraction plots show how factor analysis methods such as the Adaptive Resonance Theory-2a algorithm (ART-2a) and positive matrix factorization partition a continuum of particle compositions into a few fixed composition profiles, and they provide a simple way to characterize how ambient particle compositions change with season and/or location.
纳米气溶胶质谱仪提供了一种定量测量环境中单个 10-30nm 大小纳米颗粒元素组成的方法。在这项工作中，碳摩尔分数图被引入作为一种有效的方法来可视化环境数据集的所有颗粒组成。这些图是通过绘制数据集内每个颗粒的组成来构建的，从具有最高碳摩尔分数的颗粒开始，以具有最低碳摩尔分数的颗粒结束。该方法基于这样的观察结果：环境颗粒中的碳含量通常与氧、氮和硫呈反相关。碳摩尔分数图可以评估颗粒组成的内部混合与外部混合，并且提供了一种探索碳质物质氧化与颗粒中无机物质存在之间关系的方法。结果表明，未氧化的碳质物质主要以外部混合颗粒的形式存在，而氧化的碳质物质仅存在于含有大量无机物质的颗粒中。含有氧化碳质物质的颗粒通常是中性的，而含有未氧化碳质物质或根本不含碳的颗粒是酸性的。碳摩尔分数图展示了自适应共振理论-2a 算法 (ART-2a) 和正矩阵因子分解等因子分析方法如何将连续的颗粒组成划分为少数固定的组成分布，并且它们提供了一种简单的方法来描述环境颗粒组成如何随季节和/或位置而变化。
