Abstract View
Using Aerosol Instruments to Characterize Soot Particles Generated by Spark Discharge
ROBERT VANGUNDY, Vaithiyalingam Shutthanandan, David Bell, Dan Imre, Alla Zelenyuk, Pacific Northwest National Laboratory
Abstract Number: 218
Working Group: Carbonaceous Aerosol
Abstract
Black carbon particles are formed through incomplete combustion of materials and are important to a wide variety of atmospheric processes. To study the effects of atmospheric black carbon in the laboratory, reliable and reproducible sources are necessary. Soot particles generated by graphite spark discharge (GSD) generators are commonly used as proxy for fractal combustion soot for instrument calibration, and studies of soot reactivity, inhalation toxicity, and optical properties.
I will present the results of a recent study, in which we characterized two distinct types of soot particles generated by GSD. The first type is well-documented in literature as small, stringy, fractal like agglomerates that comprise the majority of generated particles. The second type of particles are compact agglomerates with very different shapes and morphologies.
Using a suite of state-of-the-art aerosol instruments, which include single particle mass spectrometer, scanning mobility particle sizer, centrifugal particle mass analyzer, and aerodynamic aerosol classifier, we separated in situ two types of soot particles and comprehensively characterized their properties (number concentrations, size, composition, mass, morphology, and effective density) as a function of particle size. Additionally, the separated particles were collected for microscopic analysis, confirming their distinct morphologies.
We find that compact agglomerates, comprising up to 20% of particle number concentration, have significantly higher effective densities and significantly contribute to particles mass loadings. We demonstrate the presence of compact agglomerates can lead to an apparent discontinuity in particle effective density, based on the measured particle mass and mobility diameter depending on the order of these measurements.