Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Mechanical and Aerospace Engineering

Committee Chair

Mridul Gautam

Committee Co-Chair

Aleksandar Bugarski

Committee Member

Nigel Clark

Committee Member

Mohan Krishnamurthy

Committee Member

Andrew Nix

Committee Member

Gregory Thompson


Heavy-duty natural gas engines compliant with the 2010 EPA emissions standards have a clear advantage over diesel engines in meeting regulations with minimal after-treatment configuration. Heavy-duty natural gas engines are largely promoted as a cleaner burning engine with respect to low PM mass emissions. However, lack of sufficient data and literature on the exhaust emissions from advanced natural gas engines and the potential adverse health effects has raised concern amongst regulatory agencies. Also, the ammonia emissions from three-way catalyst equipped heavy-duty natural gas engines could be a major contributor to the formation of secondary PM in the atmosphere.;This CARB funded study focuses primarily on characterizing the toxicity of the volatile fraction of PM from advanced heavy-duty natural gas engines. The objective of the study also includes characterizing the unregulated species of the exhaust together with number concentration and size distribution of ultrafine nanoparticle emissions. CNG fueled transit buses were tested on WVU's heavy-duty chassis dynamometer in Stockton, CA. A wide array of sampling procedures was included to characterize the complete chemical composition of the exhaust. The toxicity analysis included three different assays a) DHBA b) DTT and c) alveolar macrophage ROS assay.;Results of the gas phase chemical speciation results reported all carbonyl, PAH and VOC emissions close to levels found in background or below the detection limits of the analytical method. Results of elemental analysis reported elements such as calcium, phosphorus, potassium, zinc, sulfur and magnesium are some of the metals that were found in significant concentration in the PM samples. The findings of the study directly relate lubrication oil as the single most dominant source to non-volatile fraction PM emissions in the tailpipe. Both DHBA and DTT assay correlated highly with mass of elements and metals such as zinc, iron and cobalt. The DTT assay resulted in high correlation with mass of copper, zinc, phosphorus and PAH with molecular weight less than 200. The findings of this study also reported the possible formation of non-volatile nucleation mode particles of 10 nm size range.