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

• Published in: Atmospheric Measurement Techniques
• Main Authors: Schnaiter, Franz Martin, Linke, Claudia, Asmi, Eija, Servomaa, Henri, Hyvärinen, Antti-Pekka, Ohata, Sho, Kondo, Yutaka, Järvinen, Emma
• Format: Text
• Language: English
• Published: 2023
• Subjects: Arctic
• Online Access: https://doi.org/10.5194/amt-16-2753-2023; https://amt.copernicus.org/articles/16/2753/2023/

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.