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Temperature and Driving Cycle Significantly Affect Carbonaceous Gas and Particle Matter Emissions from Diesel Trucks
Michael D Hays1, William Preston2, Barbara J George3
1Office of Research and Development, National Risk Management Research Laboratory, United States Environmental Protection Agency, Research Triangle Park, North Carolina 27711, United States.
Energy & Fuels : an American Chemical Society Journal
|May 29, 2020
Summary
This study analyzed carbon emissions from diesel vehicles under various conditions. While biodiesel blends and particle filters reduced some emissions, low temperatures and cold starts increased harmful compounds, complicating emission analysis.
Area of Science:
- Environmental Science and Engineering
- Combustion Science and Engineering
- Atmospheric Chemistry
Background:
- Diesel vehicles are significant sources of gaseous and particulate emissions.
- Understanding factors influencing these emissions is crucial for air quality management.
- Biodiesel blends and advanced emission control technologies are being implemented.
Purpose of the Study:
- To investigate the impact of fuel type (ultralow sulfur diesel vs. biodiesel blend), temperature, load, and regeneration technology on carbon emissions from light and medium heavy-duty diesel vehicles (L/MHDDV).
- To analyze gas- and particle-phase emissions, including organic and elemental carbon (OC-EC) and semivolatile organic compounds (SVOCs).
- To assess the effectiveness of catalyzed diesel particle filters (CDPF) and identify factors affecting toxic polycyclic aromatic hydrocarbons (PAHs) emissions.
Main Methods:
- Chassis dynamometer testing simulating various driving conditions, temperatures (-6.7 °C to 21.7 °C), and loads (up to 12,000 kg).
- Thermal-optical analysis for OC-EC composition of aerosol particles.
- Gas chromatography/mass spectrometry for analyzing gas- and particle-phase SVOCs and PAHs.
Main Results:
- Average OC and EC emissions were 0.735 and 0.733 mg/km, respectively.
- Catalyzed diesel particle filters (CDPF) significantly reduced particle emissions, with exhaust being ~90% gas-phase matter.
- Low temperatures and cold starts markedly increased SVOC emissions; biodiesel (B20) did not significantly alter SVOCs compared to ultralow sulfur diesel (ULSD).
- Toxic PAHs (MW ≥ 252 amu) were detected downstream of CDPFs, sometimes at levels comparable to older, less controlled heavy-duty diesel vehicles.
Conclusions:
- Vehicle operating conditions like low temperature and cold starts are critical drivers of increased SVOC emissions.
- While CDPFs are effective particle traps, specific toxic compounds like PAHs can still be emitted, indicating complex exhaust stream chemistry.
- The presence of PAHs downstream of modern emission controls suggests a need for more sophisticated analysis and potentially revised emission standards for L/MHDDVs.
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