Comparison of oil and fuel particle chemical signatures with particle emissions from heavy and light duty vehicles

Abstract

In order to establish effective vehicle emission control strategies, efforts are underway to perform studies which provide insight into the origin of the source of vehicle particle emissions. In this study, the mass spectral signatures of individual particles produced from atomized auto and diesel oil and fuel samples were obtained using aerosol time-of-flight mass spectrometry (ATOFMS). The major particle types produced by these samples show distinct chemistry, falling into several major categories for each sample. Lubricating oils contain calcium and phosphate based additives and although the additives are present in low abundance (∼1–2% by mass), calcium and phosphate ions dominate the mass spectra for all new and used oil samples. Mass spectra from used oil contain more elemental carbon (EC) and organic carbon (OC) marker ions when compared to new oils and exhibit a very high degree of similarity to heavy duty diesel vehicle (HDDV) exhaust particles sampled by an ATOFMS. Fewer similarities exist between the used oil particles and light duty vehicle (LDV) emissions. Diesel and unleaded fuel mass spectra contain polycyclic aromatic hydrocarbon (PAH) molecular ions, as well as intense PAH fragment ions 25(C 2H) −, 49(C 4H) −, and inorganic ions 23Na +, 39K +, 95(PO 4) −. Unleaded fuel produced spectra which contained Na + and K +; likewise, LDV particle emission spectra also contained Na + and K +. Comparing oil and fuel particle signatures with HDDV and LDV emissions enhances our ability to differentiate between these sources and understand the origin of specific marker ions from these major ambient particle sources.