Mobile Metals Measurements Using a New Microwave-Induced Plasma Time-of-Flight Mass Spectrometer examining Roadways and Industrial Sites
EDWARD FORTNER, Alexander Gundlach - Graham, Martin Tanner, Conner Daube, Jay G. Slowik, André S. H. Prévôt, John Jayne, Douglas Worsnop, Aerodyne Research, Inc.
Abstract Number: 394
Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts
Abstract
Metals in atmospheric particles have for many years been a focus of concern related to human health. Metals also have distinct chemical fingerprints which can be utilized as chemical tracers for emissions tracking. Mobile platforms enable the measurement of microenvironments at a neighborhood level and provide the flexibility to optimize measurement locations for different wind directions. The utilization of this measurement strategy requires rapid measurements of metals. Existing metals measurement techniques are not suitable for mobile applications, which require quantitative data on timescales of ~1 min or better. X-ray fluorescence-based systems have insufficient time resolution, laser ablation/ionization mass spectrometers lack quantification, and inductively coupled plasma (ICP)-based mass spectrometers are impractical due to their reliance on an Ar-based plasma.
The microwave-induced plasma time-of-flight mass spectrometer (mipTOF), recently developed by Tofwerk AG (Schild et al., 2018), provides the time resolution, quantification and field adaptability necessary for mobile metals measurements. Unlike conventional ICP-based systems, the mipTOF uses a microwave-assisted (MICAP) plasma source sustained with N2 that maintains performance and stability during direct sampling of ambient air. The mipToF was run at 1 second time resolution and calibrations were performed daily by nebulizing a mixture of suspended 92 nm silver nanoparticles in a dissolved multi-element standard.
The mipToF was operated for 5 days on board the Aerodyne Mobile Laboratory 23 -27 March 2025. A number of roadside sources were evaluated including tunnel traffic, industrial sources such as galvanizing and electroplating facilities were sampled along with general aviation aircraft emissions. The different metals signature of these sources can be used for relative source attributions. An Aerodyne soot particle aerosol mass spectrometer (SP-AMS) also sampled alongside the mipToF for the first two days of the campaign and metals measurement comparisons are presented.
Schild, M., et al. (2018) Anal. Chem. 90, 13443-13450.