Seminar

Abstract

Gasoline and diesel engines are major contributors to air pollution problems at urban, regional, and global scales. The absolute and relative contributions from these sources are changing over time due to population growth, changes in fuels, and advances in emission control technologies. Using field measurements, the evolving contributions of gasoline and diesel engine emissions to nitrogen oxides (NOx), organic aerosols (OA), and black carbon (BC) are described over decadal time scales.

Advanced instrumentation and analytical approaches have been used to study, at an unprecedented level of chemical detail, the composition of diesel fuel and primary aerosol emissions from on-road engines. These methods feature use of softer photo-ionization techniques that greatly reduce fragmentation of parent ions during GC-MS analysis, and use of laser ablation with an aerosol mass spectrometer (SP-AMS) to measure refractory aerosol components such as black carbon and trace metals.

Diesel contributions to NOx have become increasingly dominant over time as gasoline engine emissions have been successfully controlled. Diesel contributions to primary and secondary organic aerosol concentrations also appear to be significant, increasingly so for SOA over time as gasoline-related VOC emissions have been controlled. Ambient measurement-based source apportionment studies have struggled to separate gasoline and diesel contributions to primary organic aerosol, in large part because POA emissions from both engine types are dominated by lubricating oil.