The four-wavelength Photoacoustic Aerosol Absorption Spectrometer (PAAS-4 λ )

• Published in: Atmospheric Measurement Techniques
• Main Authors: F. M. Schnaiter, C. Linke, E. Asmi, H. Servomaa, A.-P. Hyvärinen, S. Ohata, Y. Kondo, E. Järvinen
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Environmental engineering; TA170-171; Earthwork. Foundations; TA715-787; Arctic
• Online Access: https://doi.org/10.5194/amt-16-2753-2023; https://doaj.org/article/7399f90d6d3e4744b5464369678a0977

In this paper, the Photoacoustic Aerosol Absorption Spectrometer (PAAS-4 λ ) is introduced. PAAS-4 λ was specifically developed for long-term monitoring tasks in (unattended) air quality stations. It uses four wavelengths coupled to a single acoustic resonator in a compact and robust set-up. The instrument has been thoroughly characterized and carefully calibrated in the laboratory using NO 2 /air mixtures and Nigrosin aerosol. It has an ultimate 1 σ detection limit below 0.1 Mm −1 , at a measurement precision and accuracy of 3 % and 10 %, respectively. In order to demonstrate the PAAS-4 λ suitability for long-term monitoring tasks, the instrument is currently validated at the air quality monitoring station Pallas in Finland, about 140 km north of the Arctic circle. A total of 11 months of PAAS-4 λ data from this deployment are presented and discussed in terms of instrument performance. Intercomparisons with the filter-based photometers of a continuous soot monitoring system (COSMOS), the Multi-Angle Absorption Photometer (MAAP), and Aethalometer (AE33) demonstrate the capabilities and value of PAAS-4 λ , as well as for the validation of the widely used filter-based instruments.