Physiochemical and Toxicological Properties of Emissions from CNG Transit Buses, Heavy- and Light-Duty Vehicles

This page last reviewed December 23, 2013


Background

After accomplishment on the project investigating the emission from late-model heavy-duty transit buses, a.k.a. Phase I, the Air Resources Board (ARB) is leading a multi-agency research effort to investigate the emissions from heavy-duty and light-duty vehicles, a.k.a. Phase II. The project will provide a 'snapshot' of what emissions will look like in 2010 and beyond by testing vehicles with advanced after-treatment, such as particulate filters and NOx scrubbers, and using various types of fuel, such as diesel, CNG and ethanol blends. The major objective of this 4-year study focuses on the physicochemical and toxicological properties of the semi-volatile and non-volatile fractions of PM from vehicular emissions. Knowledge of how the toxicity of vehicular PM varies with particle component volatility will evaluate the design of emissions control technologies and provide a better understanding of exposure. This in turn will provide the information needed to better protect public health.

Heavy-Duty Diesel Vehicles (HDDV)

Four heavy-duty diesel vehicles in seven configurations were tested at ARB's heavy-duty diesel emission testing laboratory (HDETL) in downtown Los Angeles. The facility includes a heavy-duty chassis dynamometer, a constant volume sampling (CVS) system for measurement of THC, NOx, CO, CO2, and PM as described in 40 CFR 86, and includes specialized aerosol sampling equipment. The after-treatment devices were selected to represent technologies available to the future California on-road fleet to meet the US07 PM and US2010 NOx emission standards. The configurations include 1) a baseline vehicle without any emission control technology; 2) the same vehicle retrofitted with a combination oxidation catalyst (OC) and diesel particulate filter (DPF); 3&4) the same vehicle retrofitted as in configuration (2) with further addition of zeolite and vanadium based selective catalytic reduction systems (SCR) respectively; 5) a Caltrans truck retrofitted with diesel particulate trap with a catalytic wash-coat; 6) a diesel hybrid electric bus equipped with an OC followed by a catalyzed trap; 7) a school bus equipped with an electrically regenerated uncatalyzed DPF.

The heavy-duty diesel vehicles were tested over three driving cycles: 1) a 50 mph steady state cruise, 2) a transient cycle EPA urban dynamometer driving schedule (UDDS) and 3) idle to simulate various real-world driving conditions. Regulated emissions including PM were measured using standard CFR methods for each test. Each cycle was repeated until sufficient PM mass was loaded onto a separate set of collection substrates for chemical and toxicological analysis. Chemical speciation included PAH's, inorganic ions, organic and elemental carbon, and trace metals. Particle sizing and counting was conducted with real-time spectrometers and particle counters. Size-resolved samples were collected by a MOUDI- NanoMOUDI loaded with aluminum foil substrates. Two parallel thermal denuders were used to remove the volatile fraction of PM at temperature of 150 and 230oC, respectively. Particulate-bound PAHs and active surface area of emissions were measured in real time with commercial instruments.

The study is still ongoing. Testing one CNG transit bus with a pre-2010 engine and one with a 2010 compliant engine will be conducted next using West Virginia University's chassis dynamometer laboratory located at University of California, Riverside. Both CNG buses are equipped with exhaust after-treatment devices. The same testing protocols used for the heavy-duty diesel vehicles will be applied.

CNG Transit Buses

Testing on two CNG transit buses with 2010 compliant engines for 0.2g/bhp-hr NOx and 0.01g/bhp-hr PM standards were conducted using West Virginia University's transportable chassis dynamometer laboratory located at University of California, Riverside. Both CNG buses were equipped with exhaust after-treatment devices, three-way catalytic converters. The same testing protocols used for the heavy-duty diesel vehicles were applied for CNG transit buses over two driving cycles: 1) a 45 mph steady state cruise and 2) a transient cycle EPA urban dynamometer driving schedule (UDDS).

Light-Duty Gasoline Vehicles (LDGV)

After completion of the heavy duty testing, light-duty gasoline vehicles will be tested in at ARB's Hagen-Smit laboratory in El Monte, California. This phase of the project is still in the planning stages. It is envisioned that both a very clean and very high emitting gasoline vehicles, along with a diesel passenger car, a CNG passenger car, and an E85 vehicle will be tested.


References

Results

  • Constantinos Sioutas, (May, 2011). Physicochemical and Toxicological Assessment of the Semi-volatile and Non-volatile Fractions of PM from Heavy-duty Vehicles Operating with and without Emissions Control Technologies. ARB Research Final Report (PDF - 1,258KB)
  • Mridul Gautam et al., (July, 2011). Testing of Volatile and Nonvolatile Emissions from Advanced Technology Natural Gas Vehicles. ARB Research Final Report (PDF – 2,473KB)

Publications for Peer-reviewed Journals

  • Arvind Thiruvengadam et al., (2013). Characterization of Particulate Matter Emissions from a Current Technology Natural Gas Engine. in preparation
  • Seungju Yoon et al., (2013). Chemical and Toxicological Properties of Emissions from CNG Transit Buses Equipped with Three-Way Catalysts Compared to Lean-Burn Engines and Oxidation Catalyst Technologies. Atmospheric Environment. Link
  • Seungju Yoon et al., (2013). Criteria Pollutant and Greenhouse Gas Emissions from CNG Transit Buses Equipped with Three-Way Catalysts Compared to Lean-Burn Engines and Oxidation Catalyst Technologies. Journal of Air and Waste Management Association. Link
  • Shaohua Hu et al., (2013). Emissions of Polycyclic Aromatic Hydrocarbons (PAHs) and Nitro-PAHs from Heavy-Duty Diesel Vehicles with DPF and SCR. Journal of Air and Waste Management Association. Link
  • Oliver Chang et al., (2012). Characterization of Carbonyl and Volatile Organic Compounds (VOCs) Emissions from HDDV with PM and NOx Controls. Environmental Science and Technology. in preparation
  • Martin Shafer et al., (2011). Chemical Speciation of Vanadium and Application to Particulate Matter Emitted from Diesel Vehicles and Urban Atmospheric Aerosols. Environmental Science and Technology. in press Link
  • Jorn Herner et al., (2011). Effect of Advanced Aftertreatment for PM and NOx Reduction on Heavy-Duty Diesel Engine Ultrafine Particle Emissions. Environmental Science and Technology. Link
  • Vishal Verma, et al., (2010). Contribution of Transition Metals in the Reactive Oxygen Species Activity of PM Emissions from Retrofitted Heavy-Duty vehicles. Atmospheric Environment. Link
  • Jorn Herner et al., (2009). The Effect of Advanced Aftertreatment for PM and NOx Control on Heavy Duty Diesel Truck Emissions. Environmental Science and Technology. Link
  • Payam Pakbin et al., (2009). Characterization of Particle Bound Organic Carbon from Diesel Vehicles Equipped with Advanced Emission Control Technologies. Environmental Science and Technology. Link
  • Subhasis Biswas et al., (2009). Oxidative Potential of Semi-Volatile and Non Volatile Particulate Matter (PM) from Heavy-Duty Vehicles Retrofitted with Emission Control Technologies. Link
  • Rongsong Li et al., (2009). Ultrafine Particles from Diesel Engines Induce Vascular Oxidative Stress via JNK Activation. Free Radical Biology and Medicine. Link
  • Shaohua Hu et al., (2009). Metals Emitted from Heavy-duty Diesel Vehicles Equipped with Advanced PM and NOx Emission Controls. Atmospheric Environment. Link
  • Subhasis Biswas et al., (2008). Chemical Speciation of PM Emissions from Heavy-duty Diesel Vehicles Equipped with Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) Retrofits. Atmospheric Environment. Link
  • Subhasis Biswas et al., (2008). Physical Properties of Particulate Matter (PM) from Newer Heavy Duty Diesel Vehicles Operating with Advanced PM and NOx Emission Control Technologies. Atmospheric Environment. Link
  • Andrea Polidori et al., (2008). Real-time Characterization of Particle-bound Polycyclic Aromatic Hydrocarbons in Ambient Aerosols and from Motor-vehicle Exhaust. Atmospheric Chemistry and Physics. Link

Conference Proceedings

  • Alberto Ayala et al., (2010). Diesel Emission Research for Informing Air Quality and Climate Policy in California. Proceedings of the 6th International Exhaust Gas and Particulate Emissions Forum, March 9-10, 2010, Ludwigsburg, Germany, ISBN 978-3-00-028287-4. Paper (PDF - 5,514KB)

Conference Presentations

  • 22nd CRC On-road Emissions Workshop, March 25-28, 2012, San Diego, CA
  • Seungju Yoon et al., Comparison of Unregulated Emissions from CNG Buses with and without After-Treatment Technologies. Presentation (PDF - 944KB)
  • Jorn Herner et al., Comparison of Vehicle Exhaust across Different Fuel and Combustion Technologies. Presentation (PDF - 903KB)
  • Chandan Misra et al., Photochemical Characterization of Light Duty Vehicles Exhaust. Poster (PDF - 891KB)
  • 21st CRC On-road Emissions Workshop, March 20-23, 2011, San Diego, CA
  • Arvind Thiruvengadam et al., Unregulated Emissions, Particulate Matter Toxicity, Ammonia and Nanoparticle Emissions from a 2010 Heavy-Duty CNG Vehicles. Presentation (PDF- 1,978KB)
  • 20th CRC On-road Emissions Workshop, March 22-24, 2010, San Diego, CA
  • Shaohua Hu et al., Characterization of a Non-Catalyzed, Electrically Heated DPF: Performance and Emission Control. Presentation (PDF - 1,035KB)
  • Shaohua Hu et al., Urea-Based Selective Catalytic Reduction (SCR) for HDDVS: Chemistry, Physics, and Toxicology of Emissions. Poster (PDF - 1,199KB)
  • 28th American Association of Aerosol Research (AAAR) Annual Conference, October 26-30, 2009, Minneapolis, MN
  • Jorn D. Herner et al., The Effect of Diesel Particulate Filters and Selective Catalytic Reduction - A Predictive Framework for Ultrafine Particle Formation, Toxicity and Chemical Composition. Presentation (PDF - 1,238KB)
  • Shaohua Hu et al., Characterization of Polycyclic Aromatic Hydrocarbons (PAH) and Nitro-PAH Emissions from HDDV with PM and NOx Controls. Poster (PDF - 1,211KB)
  • 2009 Directions in Engine-efficiency and Emissions Research (DEER) Conference, August 3-6, 2009, Dearborn, MI
  • Shaohua Hu, et al., Effects of Catalysts on Emissions from Heavy-duty Diesel Retrofits for PM and NOx Control. Abstract (PDF - 10KB)
  • 13th ETH Conference on Combustion Generated Nanoparticles, June 22-24 2009, Zürich, Switzerland
  • Alberto Ayala et al., Regeneration, Volatile Nanoparticles, Toxicity, and Other Research Questions for Diesel Emission Controls. Presentation (PDF - 1,169KB)
  • 19th CRC On-road Emissions Workshop, March 23-25, 2009, San Diego, CA
  • Shaohua Hu et al., DPF + SCR Retrofits and Their Impact on Diesel Emissions. Presentation (PDF - 1,387KB)
  • 2008 CRC Mobile Source Air Toxics Workshop, December 1-3, 2008, Phoenix, AZ
  • Shaohua Hu et al., Emissions from HD Diesel Retrofits for PM and NOx Control. Presentation (PDF - 3,483KB)
  • 27th American Association for Aerosol Research (AAAR) Annual Conference, October 20-24, 2008, Rosen Shingle Creek, Orlando, FL
  • Martin Shafer et al., Novel Approaches for Speciation of Platinum and Vanadium in Mobile Source Emissions. Presentation (PDF - 815KB)
  • Alberto Ayala et al., Ionic and Organic Species in PM Emissions from Advanced Technology Heavy Duty Diesel Vehicles. Presentation (PDF - 2,672KB)
  • Shaohua Hu et al., Chemical Speciation of PM Emissions from Heavy Duty Diesel Vehicles Equipped with Diesel Particulate Filter (DPF) and SCR Retrofits.
  • Subhasis Biswas et al., Toxicity of Particulate Matter from Heavy-Duty Vehicles Retrofitted with Emission Control Technologies.
  • Jorn D. Herner et al., Metals from Heavy-duty Diesel Vehicles Equipped with Advanced PM and NOx Emission Controls. Poster (PDF - 983KB)
  • 12th ETH Conference on Combustion Generated Nanoparticles, June 23-25, 2008, Zürich, Switzerland
  • Constantinos Sioutas et al., Physicochemical and Toxicological Assessment of Semi-volatile and Non-volatile PM from Heavy-Duty Vehicles Operating with and without Advanced Emission Control Technologies. Presentation (PDF - 487KB)
  • 18th CRC On-Road Emissions Workshop, March 31 - April 2, 2008, San Diego, CA
  • Jorn D. Herner et al., CARB's Phase II Study: Project Overview and NOx, PM, and Nanoparticle Emissions. Presentation (PDF - 672KB)
  • M.-C. Oliver Chang et al., Air Toxic Emissions from HD Diesel Vehicles Equipped with NOx and PM Retrofits. Presentation (PDF - 1,382KB)
  • 26th American Association for Aerosol Research (AAAR) Annual Conference, September 24-28, 2007, Reno, NV
  • Jorn D. Herner et al., Nucleation Mode Particle Emissions from In-use Heavy Duty Vehicles Equipped with DPF and SCR Retrofits. Presentation (PDF - 2,386KB)
  • Shaohua Hu et al., Physical Properties of Particulate Matter (PM) from Newer Heavy Duty Diesel Vehicles Operating with Advanced Emission Control Technologies. Presentation (PDF - 222KB)
  • Jorn D. Herner et al., Towards 2010 NOx and PM emission Levels: Overview of CARB's Investigation of Advanced Heavy-duty On-road Vehicle Retrofits and Other Technologies. Poster (PDF - 983KB)
  • M.-C. Oliver Chang et al., Chemistry of Air Toxics Emitted from In-use Heavy Duty Vehicles Equipped with DPF and SCR Retrofits. Poster (PDF - 178KB)
  • 11th ETH International Conferences on Combustion Generated Nanoparticles, August 12-15, 2007, Zürich, Switzerland
  • Jorn D. Herner et al., Nanoparticles from a California In-Use Heavy Truck Equipped With PM-NOx Retrofits. Poster (PDF - 538KB)
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