Project: Secondary Pollutants Emitted in Vehicle Exhaust

Project Background:

Catalytic converters have been instrumental in reducing major pollutant exhaust emissions from light duty motor vehicles and have played a significant role in improving air quality. However, secondary reactions (i.e., post-combustion) on the catalyst may produce unregulated emissions (e.g., hydrogen cyanide, HCN, and ammonia, NH₃) that could have an adverse impact on human health and the environment. Of particular concern is a highly toxic class of compounds termed (chemically-)reduced nitrogen compounds (RNCs) that include HCN; N-nitrosamines; amines; hydrazine; methylhydrazine; hydroxylamine; as well as their reaction products with co-emitted aldehydes, where relevant. While these compounds have received little attention in the past, their presence in vehicle exhaust, even at low concentrations, could lead to significant adverse health effects, particularly in high exposure scenarios such as freeway communities, vehicle cabins, and enclosed spaces (e.g., residential and parking garages). Over the past 5 years, two faculty members, two postdoctoral associates, and three undergraduate students at Oak Crest have investigated RNC emissions by motor vehicles. We developed a novel remote sensing instrument capable of measuring over 20 compounds emitted in vehicle exhaust and used this device in parking lot¹ and freeway on-ramp studies.^2,3 One important accomplishment was the first-ever measurement of NH₃ in vehicle exhaust by remote sensing, which allowed us to determine mean fleet NH₃ emission rates of 36 mg-km^-1 from measurements on exhaust emitted by 2091 vehicles as they traveled up a Southern California freeway on-ramp. These findings could have significant implications on air quality in the Los Angeles area, since ammonium salts are primarily present in the atmosphere as fine particles, which have been associated with numerous deleterious health effects.

Project Description:

The successful applicant will investigate the importance of nitroso- (R-NO) and nitro- compounds (R-NO₂) within the context of vehicular exhaust emissions. This project will interface with Oak Crest’s current activities in this area and will be divided into two main phases: (1) development of a method for the collection and analysis of the above compounds; and (2) field measurements aimed at determining the magnitude of these emissions from vehicle exhaust. Prior experience in analytical and organic chemistry will be viewed favorably.

1)   Baum, M. M.; Kiyomiya, E. S.; Kumar, S.; Lappas, A. M.; Lord, H. C., III "Multi-Component Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 1. Effect of Fuel Type and Catalyst Performance". Environ. Sci. Technol. 2000, 34, 2851-2858.

2)   Baum, M. M.; Kiyomiya, E. S.; Kumar, S.; Lappas, A. M.; Kapinus, V. A.; Lord, H. C., III "Multi-Component Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-road Ammonia Measurements". Environ. Sci. Technol. 2001, 35, 3735-3741.

3)   Baum, M. M.; Kiyomiya, E. S.; Kumar, S.; Lappas, A. M.; Kapinus, V. A.; Lord, H. C. "Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-road Ammonia Measurements (Vol 35, Pg 3735, 2001)". Environ. Sci. Technol. 2002, 36, 4705-4705.