Preprints
https://doi.org/10.5194/amt-2022-155
https://doi.org/10.5194/amt-2022-155
16 May 2022
 | 16 May 2022
Status: this preprint was under review for the journal AMT but the revision was not accepted.

Performance analysis of the NanoScan SMPS and the Mini WRAS Ultrafine Aerosol Particle Size Spectrometers

Ajit Ahlawat, Kay Weinhold, Jesus Marval, Paolo Tronville, Ari Leskinen, Mika Komppula, Holger Gerwig, Lars Gerling, Stephan Weber, Rikke Bramming Jørgensen, Thomas Nørregaard Jensen, Marouane Merizak, Ulrich Vogt, Carla Ribalta, Mar Viana, Andre Schmitz, Maria Chiesa, Giacomo Gerosa, Lothar Keck, Markus Pesch, Gerhard Steiner, Thomas Krinke, Torsten Tritscher, Wolfram Birmili, and Alfred Wiedensohler

Abstract. In aerosol science, there is an increasing interest to perform mobile measurements to obtain number size distribution of ultrafine particles (UFP), using portable instruments based on unipolar charging and size segregation by electrical particle mobility. Applications of such measurements range from ambient and indoor aerosol studies to source identification in work environments. However, knowledge on the actual measurement uncertainties of these portable instruments under various conditions has been limited. This investigation presents results from an intercomparison workshop conducted at the World Calibration Center for Aerosol Physics (WCCAP) in Leipzig, Germany, in January 2020. Manufacturers and users were invited to have their portable instruments tested and compared against reference instrumentation for particle number size distributions (PNSD) and total particle number concentration (PNC). In particular, the performances and uncertainties of the NanoScan SMPS (Scanning Mobility Particle Sizer) Model 3910 (TSI Inc.) and the Mini Wide Range Aerosol Spectrometer (WRAS) Model 1371 (Grimm Aerosol Technik) were investigated extensively against the WCCAP Mobility Particle Size Spectrometers (MPSS) and Condensation Particle Counters (CPC). A total of 11 TSI NanoScan SMPS and 4 GRIMM Mini WRAS instruments were characterized for ambient aerosols as well as lab-generated aerosols.

The workshop results affirm that the portable instruments must be serviced and calibrated annually or prior field studies to provide measurements within the given uncertainties. It should be noted that users should carry out timely service, maintenance and calibration of portable instruments at their facilities. During initial inspection, non-serviced NanoScan SMPS instruments overestimated a dominant ultrafine aerosol mode by 120 % at around 80 nm. Maintenance and servicing improved the performance. Overall, the performance of NanoScan SMPS instruments improved for the ultrafine aerosol mode while the PNC in the fine aerosol mode still overestimated by up to 80 %. The latter effect seems to be systematically related to the unipolar charging of particles, and the reduced sensitivity of electrical particle mobility with increasing particle size above 200 nm. Due to shift in the second mode of bimodal distribution, particles are overcounted around 100 nm. With regard to the integral PNC, some of the NanoScan SMPS found to be in good agreement (i.e. within 20 %) compared to the reference CPC. In addition, a reasonably good unit-to-unit agreement within ±20 % was found for NanoScan SMPS instruments. The Mini WRAS instruments, after proper cleaning and servicing, provided improved results within ±15 % deviation in PNC in the ultrafine aerosol mode. Overall, most of the GRIMM Mini WRAS instruments (operating with software version 10.0) agrees well with PNC (i.e. 10–50 %) when the ultrafine mode was dominant. Conversely, PNC of the fine aerosol mode was systematically underestimated by 60 % above 100 nm. Except for one instrument, the integral PNC of the GRIMM Mini WRAS spectrometers were within an uncertainty range of ±20 % compared to the reference CPC. Additionally, it is important for users to note that the Mini WRAS performed significantly better when using software version 10.0 compared to version 8.2.

The workshop results suggest that despite the above-mentioned uncertainties, these portable instruments are suited for mobile ultrafine particle measurements to detect relative differences in the PNSD such as source apportionment studies of ultrafine particles at work places or outdoors near sources.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Ajit Ahlawat, Kay Weinhold, Jesus Marval, Paolo Tronville, Ari Leskinen, Mika Komppula, Holger Gerwig, Lars Gerling, Stephan Weber, Rikke Bramming Jørgensen, Thomas Nørregaard Jensen, Marouane Merizak, Ulrich Vogt, Carla Ribalta, Mar Viana, Andre Schmitz, Maria Chiesa, Giacomo Gerosa, Lothar Keck, Markus Pesch, Gerhard Steiner, Thomas Krinke, Torsten Tritscher, Wolfram Birmili, and Alfred Wiedensohler

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Ajit Ahlawat, Kay Weinhold, Jesus Marval, Paolo Tronville, Ari Leskinen, Mika Komppula, Holger Gerwig, Lars Gerling, Stephan Weber, Rikke Bramming Jørgensen, Thomas Nørregaard Jensen, Marouane Merizak, Ulrich Vogt, Carla Ribalta, Mar Viana, Andre Schmitz, Maria Chiesa, Giacomo Gerosa, Lothar Keck, Markus Pesch, Gerhard Steiner, Thomas Krinke, Torsten Tritscher, Wolfram Birmili, and Alfred Wiedensohler
Ajit Ahlawat, Kay Weinhold, Jesus Marval, Paolo Tronville, Ari Leskinen, Mika Komppula, Holger Gerwig, Lars Gerling, Stephan Weber, Rikke Bramming Jørgensen, Thomas Nørregaard Jensen, Marouane Merizak, Ulrich Vogt, Carla Ribalta, Mar Viana, Andre Schmitz, Maria Chiesa, Giacomo Gerosa, Lothar Keck, Markus Pesch, Gerhard Steiner, Thomas Krinke, Torsten Tritscher, Wolfram Birmili, and Alfred Wiedensohler

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Short summary
Measurements of ultrafine particles must be done with quality-assured instruments. The performance of portable instruments such as NanoScan SMPS, and GRIMM Mini WRAS spectrometer measuring the particle number size distribution in the range from 10 to 200 nm were investigated. The influence of different aerosol types and maintenance activities on these instruments were explored. The results show that these portable instruments are suitable for mobile UFP measurements for source identification.