Aerosol optical properties monitoring.

At the Gruvebadet Aerosol Laboratory (GAL) aerosol scattering coefficient is measured at a single wavelength (530 nm) using a Radiance Research nephelometer. Data is acquired continuously at 1-minute time resolution. Aerosol light absorption is measured at three wavelengths with a Radiance Research PSAP at 1-minute time resolution at 467 nm, 530 nm, and 660 nm.

For the scattering coefficient the truncation error correction is performed according to Muller et al. (2009) and assuming a scattering angstrom exponent of 1.15 (Schmeisser et al., 2018). For absorption coefficient, the PSAP measurements are corrected according to Bond et al. (1999) for flow and sampling filter area and according to Virkkula et al. (2011) for loading and shadowing effect, using simultaneous scattering coefficient measurements. For all the aerosols instruments, quality control procedures will include periodic flow calibration, and blank measurements using a HEPA filter to detect potential leak and verify the instrumental detection limit. In addition, the aethalometer quality assurance procedure will include the leak check to test and quantify the presence potential leaks, the stability test to verify sensors noise, and the optical performance test to check for the detector response at the different operating wavelengths. Both absorption and scattering coefficient measurements are normalized at standard pressure and temperature conditions (1 atm and 0 degC), averaged over a 1-hour period, and provided at all available wavelengths.

Müller, T., Nowak, A., Wiedensohler, A., Sheridan, P., Laborde, M., Covert, D.S., Marinoni, A., Imre, K., Henzing, B., Roger, J.C., Martins dos Santos, S., Wilhelm, R., Wang, Y.Q., de Leeuw, G. (2009) Angular Illumination and Truncation of Three Different Integrating Nephelometers: Implications for Empirical, Size-Based Corrections, Aerosol Science and Technology, 43:6, 581-586, DOI: 10.1080/02786820902798484;

Schmeisser, L., Backman, J., Ogren, J. A., Andrews, E., Asmi, E., Starkweather, S., Uttal, T., Fiebig, M., Sharma, S., Eleftheriadis, K., Vratolis, S., Bergin, M., Tunved, P., and Jefferson, A.: Seasonality of aerosol optical properties in the Arctic, Atmos. Chem. Phys., 18, 11599-11622, https://doi.org/10.5194/acp-18-11599-2018 , 2018;

Bond, T.C., Anderson, T.L., Campbell, D. (1999) Calibration and Intercomparison of Filter-Based Measurements of Visible Light Absorption by Aerosols, Aerosol Science and Technology, 30:6, 582-600, DOI: 10.1080/027868299304435;

Virkkula, A., Backman, J., Aalto, P. P., Hulkkonen, M., Riuttanen, L., Nieminen, T., dal Maso, M., Sogacheva, L., de Leeuw, G., and Kulmala, M.: Seasonal cycle, size dependencies, and source analyses of aerosol optical properties at the SMEAR II measurement station in Hyytiälä, Finland, Atmos. Chem. Phys., 11, 4445-4468, https://doi.org/10.5194/acp-11-4445-20 11, 2011.

ISO 19139

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