Real world cold-start emissions measurements in a parking garage

Despite progress in emission reductions, motor vehicles are a significant contributor to urban air pollution, releasing emissions containing various compounds in both particulate and gas phases. Studies have shown that the highest emissions are exhibited during the cold start due to the inefficient operation of the catalyst and engine at low temperature (Kontses et al. 2020; Hu et al. 2023).

This study aims to enhance our understanding of cold-start emissions from passenger cars, which dominate urban traffic. To achieve this, emissions of a vehicle fleet were measured under realistic conditions within a parking garage. The measurements were conducted from November 27 to December 24, 2024, in  an undergraduate parking garage with  250 parking  spaces, located in a shopping mall in Patras, Greece. The particle phase was measured by a scanning mobility particle sizer (SMPS), a high-resolution aerosol mass spectrometer (HR-ToF-AMS) and a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHARON inlet (Ionicon Analytik Inc.). Black carbon was quantified by an Aethalometer (AE33) and a Single Soot Photometer (SP²-XR). An Electrical Low-Pressure Impactor (ELPI, Dekati) was also operated on site. The gas-phase composition was characterized by the PTR-MS while trace gases such as NO, NO₂, CO, CO₂, O₃ and SO₂ were continuously monitored. For offline analysis, samples were collected using quartz filters and Tenax tubes.  Additionally, the traffic flow was recorded at both the entrance and exit of the garage. Measurements of CO₂ were conducted at six different locations in the garage and indicated that the measurements were representative of most of the volume of the structure.

The measured concentrations varied significantly during the day with peaks in the morning and the evening. The measurements of the traffic and the concentrations were combined to derive average emissions of gas and particulate phase pollutants per cold start and per kilogram of fuel.

 

References

Kontses, A., Triantafyllopoulos, G., Ntziachristos, L., and Samaras, Z. 2020. Particle number (PN) emissions from gasoline, diesel, LPG, CNG and hybrid-electric light-duty vehicles under real-world driving conditions, Atmos. Environ., 222, 117126.

Hu, J., Frey, H. C., and Boroujeni, B. Y. (2023). Contribution of cold starts to real-world trip emissions for light-duty gasoline vehicles. Atmosphere, 14, 35.