The UFP number concentration and number size distribution have been measured at an urban background site in Wildau (Brandenburg, Germany) during the entire year 2024. The employed measurement devices included a Condensation Particle Counter (Grimm 5421-CEN), fully compliant with EN16976 and a Mobility Particle Size Spectrometer (Grimm SMPS+C 5420-CEN) according to CEN/TS 17434. In addition, a Partector 2 and Partector 2 Pro (naneos) were employed as simplified methods to measure the number concentration and size distribution, respectively. The results show that all devices can reliably be applied with reasonably good comparability of the results.

In the context of the project “MITIGATING TRANSPORT-RELATED AIR POLLUTION IN EUROPE (MI-TRAP)”, an MPSS calibration workshop took place in Prague, Czech Republic from November 25, 2024 to December 2, 2024. One of the participating instruments (a negative polarity MPSS) displayed significant difference (~25%) from the reference MPSS (positive polarity). A regularization based inversion method was applied so as to harmonize measurements acquired by the participating instrument with those obtained from a reference instrument.

Faraday Cup Aerosol Electrometers (FCAE) are the preferred reference instrument for CPCs used stand alone or used as detector in an MPSS setup. So far, the standard method to calibrate FCAE involves rather extensive and stationary instrumentation, involving high precision laboratory-based instrumentation, mostly only available at dedicated national metrology institutes that also have specialized in the field of low current measurement. Here we present data and the use of a commercially available Ultra-stable Low-noise Current Amplifier (ULCA) for the calibration of a GRIMM FCE 5705, teamed up with the newly developed GRIMM FCE Controller 5704.

Condensation Particle Counters (CPCs) are widely-used instruments for atmospheric measurements of the particle number (PN) concentration. EN 16976:2024 compliant CPC work with butanol and have D50 of 10 nm. A water-based V-WCPC (3789) allows custom temperature settings and was calibrated. It was found that the different temperature settings from calibrations with sucrose and silver (in N₂) particles were different and then used to measure ambient aerosol with 3 units of V-WCPC and in parallel with a fully compliant CPC (3750-CEN10). They show an overall good agreement for ambient air in Aachen when using the sucrose-based calibration for the V-WCPC.