Emissions from Diesel and Gasoline Engines Measured in Highway Tunnels. Part 1: Real-World Particulate Matter and Gaseous Emissions from Motor Vehicles in a Highway Tunnel. Part 2: Airborne Carbonyls from Motor Vehicle Emissions in Two Highway Tunnels

摘要

Studies link atmospheric particulate matter with human health problems. In many urban areas, mobile sources are a major source of PM and the dominant source of fine particles or PM2.5. Information about particle emission rates, size distributions, and chemical composition from in-use light-duty (LD) gasoline and heavy-duty (HD) diesel vehicles is scares. To characterize particulate emission from in-use vehicles, we studied emissions from vehicles operating under hot-stabilized conditions, at relatively constant speed, in the Tuscarora Mountain Tunnel along the Pennsylvania Turnpike. Comparing the results of this study with our 1992 results, we found that emission of C8 to C20 hydrocarbons, carbon monoxide (CO), and carbon dioxide (CO2) from HD diesel emissions substantially decreased. Particulate mass emissions showed a similar trend. We observed a continued downward trend in HD particulate emissions from approximately 1,100 mg/km in 1974 to 132 mg/km (reported as PM2.5) in this study. The LD particle emission factor was considerably less than the HD value, but given the large fraction of LD vehicles, emissions from this source cannot be ignored. Results of this study also indicate that HD and LD vehicles emit ultrafine particles and that they are preserved under real-world dilution conditions. These particles appear to be primarily composed of sulfur, indicative of sulfuric acid emission and nucleation. Comparing the 1992 and 1999 HD oxides of nitrogen (NO-x) emission rates, we observed a 48% increase in emission. This finding supports the assumption that many new-technology diesel engines conserve fuel but increase NO-x emissions.