Preprints
https://doi.org/10.5194/egusphere-2023-2692
https://doi.org/10.5194/egusphere-2023-2692
21 Dec 2023
 | 21 Dec 2023
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

Estimating errors in vehicle secondary aerosol production factors due to oxidation flow reactor response time

Pauli Simonen, Miikka Dal Maso, Pinja Prauda, Anniina Hoilijoki, Anette Karppinen, Pekka Matilainen, Panu Karjalainen, and Jorma Keskinen

Abstract. Oxidation flow reactors used in secondary aerosol research do not immediately respond to changes in the inlet concentration of precursor gases because of their broad transfer functions. This is an issue when measuring the vehicular secondary aerosol formation in transient driving cycles because the secondary aerosol measured at the oxidation flow reactor outlet does not correspond to the rapid changes in the exhaust flow rate. Since the secondary aerosol production factor is determined by multiplying the secondary aerosol mass with the exhaust flow rate, the misalignment between the two leads to incorrect production factors. This study evaluates the extent of the error in production factors due to oxidation flow reactor transfer functions by using synthetic and semi-synthetic exhaust emission data. It was found that the transfer function-related error could be eliminated when only the total production factor of full cycle was measured using constant volume sampling. For shorter segments within a driving cycle, a narrower transfer function led to smaller error. Even with a narrow transfer function, the oxidation flow reactor could report production factors that were more than 10 times higher than the true production factors if the segment duration was too short.

Pauli Simonen, Miikka Dal Maso, Pinja Prauda, Anniina Hoilijoki, Anette Karppinen, Pekka Matilainen, Panu Karjalainen, and Jorma Keskinen

Status: open (until 29 Feb 2024)

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  • RC1: 'Comment on egusphere-2023-2692', Anonymous Referee #1, 16 Feb 2024 reply
  • RC2: 'Comment on egusphere-2023-2692', Anonymous Referee #2, 23 Feb 2024 reply
Pauli Simonen, Miikka Dal Maso, Pinja Prauda, Anniina Hoilijoki, Anette Karppinen, Pekka Matilainen, Panu Karjalainen, and Jorma Keskinen
Pauli Simonen, Miikka Dal Maso, Pinja Prauda, Anniina Hoilijoki, Anette Karppinen, Pekka Matilainen, Panu Karjalainen, and Jorma Keskinen

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Short summary
Secondary aerosol is formed in atmosphere from gaseous emissions. Oxidation flow reactors used in secondary aerosol research do not immediately respond to changes in the inlet concentration of gases because of their broad transfer functions. This may result in incorrect secondary aerosol production factors determined for vehicles. We studied the extent of possible error and found that oxidation flow reactors with faster response result in smaller error.