Spatial Analysis of Remotely Sensed Vehicle Exhaust Emissions from Light Duty Gasoline Vehicles in Clark County, Nevada

摘要

A novel Lidar-based remote sensing system was assembled and used to measure light scattering from particulate matter (PM) emitted from in-use on-road vehicles. A commercially available remote sensing system was also used to measure emissions of carbon monoxide (CO), nitrogen oxide (NO), and hydrocarbons (HC). The two systems were used to measure 61,207 gasoline and 1,180 diesel-powered vehicle emissions in Las Vegas, NV from 04/04/2000 to 5/16/2002. Emission factors were related to vehicle age, weight class, and fuel type by matching license IDs to the state registration. Relationships between vehicle emissions factors and light duty gasoline vehicle age were established for each of the pollutants measured. The Nevada Department of Transportation database of vehicles registered in Clark County was analyzed to identify "hot spots" of older vehicles and consequently higher average emission factors. The spatial density of registered vehicles was multiplied by the average emission factor of all registered vehicles in each census block. The region of the Las Vegas urban area with the greatest concentration of high emitting vehicles coincided with the area of peak 8 hour CO concentration in a recent air quality study. Based on this analysis, current modeling efforts using fleet-averaged distance-based emissions factors coupled with estimates of vehicle kilometers traveled on roadway networks omit an important predictor of the spatial distribution of vehicle emissions. Residents in neighborhoods with dense concentrations of older vehicles are likely to be exposed to higher vehicle exhaust emissions than are predicted with current mobile modeling techniques. These results also have important implications for the design of air quality monitoring networks that are intended to represent ambient concentrations in areas of highest pollutant exposure.