Measuring Urban Aerosol Volatility Fractions with a Catalytic Stripper at an ACTRIS Aerosol Observatory: Characterization and Implementation

 Aerosol particles play a central role in atmospheric processes, influencing air quality, human health, and climate. To fully understand these impacts, it is essential to quantify not only the physical properties such as concentration or size but also their chemical composition. Offline chemical analysis of aerosol samples or online mass spectrometry are generally complicated or expensive. Another efficient method is to determine the partitioning between the volatile and non-volatile fractions. This information provides insight into the chemical composition of an air mass and allows to infer information about aerosol sources, chemical aging, and transformation processes in the atmosphere (e.g. Weinzierl et al. (2006); Wehner et al. (2005, 2009); Ehn et al. (2007)).

A catalytic stripper (CS) is commonly used to separate the volatile and semi-volatile fraction from the solid aerosol particles, which allows for precise measurement of the non-volatile fraction and the total aerosol load (Swanson and Kittelson, 2010). Compared to a thermal denuder, it has the advantage that volatile substances undergo catalytic transformation and cannot recondense into particles after treatment. The CS has successfully been used in many automotive applications such as Particle Measurement Program (PMP) compliant studies (Giechaskiel et al., 2020; Swanson and Kittelson, 2010). However, not many atmospheric aerosol studies apply this simple distinction between volatile and solid particles, which plays an important factor for the investigation of air quality, human health and climate impact of aerosols.

Here we present the application of a CS for measurements of non-volatile aerosol particles at the Aerosol Observatory of the University of Vienna which is on track to become a National Facility for aerosol in-situ observations within the pan-European Aerosol, Clouds, and Trace Gas Research Infrastructure ACTRIS. This study includes the characterization of the CS with respect to particle penetration and removal efficiency of volatile and semi-volatile components. For particle penetration silver particles were generated with the Silver Particle Generator (SPG) and treated by the Sintering Stage S8000 to obtain thermally stable silver spheres in the size range between 2nm and 100nm. The characterization of the removal efficiency of volatile and semi-volatile particles is done with tetracontane, which is a well-established method in many regulations for the testing of volatile particle removal (VPR) systems in the automotive section (e.g. Euro-7). The aim of this study is to present initial results from continuous measurements of the non-volatile aerosol fraction over several weeks at the Aerosol Observatory in Vienna, demonstrating their potential for source identification and chemical characterization, and highlighting the importance of non-volatile particle measurements.

 

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