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Ghadimi S, Zhu H, Durbin TD, Cocker DR, Karavalakis G. Exceedances of Secondary Aerosol Formation from In-Use Natural Gas Heavy-Duty Vehicles Compared to Diesel Heavy-Duty Vehicles. Environ Sci Technol 2023; 57:19979-19989. [PMID: 37988584 DOI: 10.1021/acs.est.3c04880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2023]
Abstract
This work, for the first time, assessed the secondary aerosol formation from both in-use diesel and natural gas heavy-duty vehicles of different vocations when they were operated on a chassis dynamometer while the vehicles were exercised on different driving cycles. Testing was performed on natural gas vehicles equipped with three-way catalysts (TWCs) and diesel trucks equipped with diesel oxidation catalysts, diesel particulate filters, and selective catalytic reduction systems. Secondary aerosol was measured after introducing dilute exhaust into a 30 m3 environmental chamber. Particulate matter ranged from 0.18 to 0.53 mg/mile for the diesel vehicles vs 1.4-85 mg/mile for the natural gas vehicles, total particle number ranged from 4.01 × 1012 to 3.61 × 1013 for the diesel vehicles vs 5.68 × 1012-2.75 × 1015 for the natural gas vehicles, and nonmethane organic gas emissions ranged from 0.032 to 0.05 mg/mile for the diesel vehicles vs 0.012-1.35 mg/mile for the natural gas vehicles. Ammonia formation was favored in the TWC and was found in higher concentrations for the natural gas vehicles (ranged from ∼0 to 1.75 g/mile) than diesel vehicles (ranged from ∼0 to 0.4 g/mile), leading to substantial secondary ammonium nitrate formation (ranging from 8.5 to 98.8 mg/mile for the natural gas vehicles). For the diesel vehicles, one had a secondary ammonium nitrate of 18.5 mg/mile, while the other showed essentially no secondary ammonium nitrate formation. The advanced aftertreatment controls in diesel vehicles resulted in almost negligible secondary organic aerosol (SOA) formation (ranging from 0.046 to 2.04 mg/mile), while the natural gas vehicles led to elevated SOA formation that was likely sourced from the engine lubricating oil (ranging from 3.11 to 39.7 mg/mile). For two natural gas vehicles, the contribution of lightly oxidized lubricating oil in the primary organic aerosol was dominant (as shown in the mass spectra analysis), leading to enhanced SOA mass. Heavily oxidized lubricating oil was also observed to contribute to the SOA formation for other natural gas vehicles.
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Affiliation(s)
- Sahar Ghadimi
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, 1084 Columbia Avenue, Riverside, California 92507, United States
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
| | - Hanwei Zhu
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, 1084 Columbia Avenue, Riverside, California 92507, United States
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
| | - Thomas D Durbin
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, 1084 Columbia Avenue, Riverside, California 92507, United States
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
| | - David R Cocker
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, 1084 Columbia Avenue, Riverside, California 92507, United States
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
| | - Georgios Karavalakis
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, 1084 Columbia Avenue, Riverside, California 92507, United States
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
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