Evaluation of the point sampling method and inter-comparison of remote emission sensing systems for screening real-world car emissions

Markus Knoll; Martin Penz; Christina Schmidt; Denis Pöhler; Tommaso Rossi; Simone Casadei; Yoann Bernard; Ǻsa M Hallquist; Ǻke Sjödin; Alexander Bergmann

doi:10.1016/j.scitotenv.2024.171710

Evaluation of the point sampling method and inter-comparison of remote emission sensing systems for screening real-world car emissions

Sci Total Environ. 2024 Mar 28:171710. doi: 10.1016/j.scitotenv.2024.171710. Online ahead of print.

Authors

Affiliations

¹ Institute of Electric Measurement and Sensor Systems, Graz University of Technology, Inffeldgasse 33/I, Graz 8010, Austria. Electronic address: markus.knoll@tugraz.at.
² Institute of Electric Measurement and Sensor Systems, Graz University of Technology, Inffeldgasse 33/I, Graz 8010, Austria.
³ Institute of Environmental Physics, Heidelberg University, INF 229, Heidelberg 69120, Germany; Airyx GmbH, Justus-von-Liebig-Str. 14, Eppelheim 69214, Germany.
⁴ Innovhub - Stazioni Sperimentali per l'Industria S.r.k., Sustainable Mobility Team, Via G. Galilei 1, San Donate Milanese, Milan 20097, Italy.
⁵ ICCT International Council on Clean Transportation, Neue Promenade 6, Berlin 10178, Germany.
⁶ IVL Swedish Environmental Research Institute, Valhallavaegen 81, Stockholm 10031, Sweden.

PMID: 38554971
DOI: 10.1016/j.scitotenv.2024.171710

Abstract

Emissions from internal combustion vehicles are currently not properly monitored throughout their life cycle. Remote emission sensing (RES) is a technology that can measure emissions under real driving conditions without contact. Current light extinction based RES systems are capable of providing emission factors for various gases, but lack accuracy for particulate matter (PM). Point Sampling (PS) is an extraction-based RES technique that can measure gases as well as various particle metrics such as black carbon or particle number. In this work, we evaluated the performance of a recently developed PS system and the state-of-the-art light extinction based remote sensing devices EDAR (HEAT) and ORSD (OPUS RSE) during co-location measurements. Validation measurements with portable emission measurement systems and emissions screening of several thousand cars in three European cities provide detailed insights into system's performance. Meteorological evaluations showed that the PS capture rate is strongly influenced by wind, but no other weather influences were found. Both light extinction based systems are unable to measure during rain. We found that all three systems tested were capable of screening NO_x emissions from pre-Euro 6 diesel cars. Measurement results show the ability of the PS system to quantify high and low PM emitters equally well. The open-path RES systems (EDAR, ORSD) are capable of estimating PM emissions from pre-Euro 5 diesel cars. However, deficiencies of open-path RES systems are evident in the quantification of PM emissions from newer engine technologies (diesel Euro 5 and beyond) and from petrol cars. The PS system has a 2 to 5 times lower capture rate than open-path RES systems, but the PS measurement results are more accurate (more than 5 times for PM and more than 1.35 times for NO_x). The good accuracy of individual measurements makes PS a powerful tool for reliable high emitter identification.

Keywords: Air pollution; Point sampling; Real world driving emissions; Remote emission sensing; Validation study; Vehicle emission screening.