On-road Mobile Source Emissions in Tennessee for 2002 – an Inventory and Analysis

Author

Jeongran Yun, University of Tennessee - Knoxville

Date of Award

8-2004

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

Terry L. Miller

Committee Members

Wayne T. Davis, Arun Chatterjee

Abstract

Annual on-road mobile source emissions must be updated every three years according to the U.S. Environmental Protection Agency (EPA). The year 2002 is the most recent year to update the emission inventory. The EPA’s computer model, MOBILE6.2, was used to develop the inventory, and the results presented in this report. Emissions of VOC, CO, NO_X, SO₂, NH₃, PM2.5, PM10, and CO₂ were estimated for each of the 95 counties in the state of Tennessee. The latest available traffic data for the year 2002 obtained from the Tennessee Department of Transportation (TDOT) were used to estimate emissions. This data included the estimates of vehicle speeds, truck mix, and vehicle miles of travel, by county and roadway type.

Monthly average values of min/max temperatures, absolute humidity, and fuel RVP were used to obtain monthly and annual emissions. Annual emissions from monthly estimates were compared to emissions estimated by using annual average inputs of temperature, absolute humidity, and fuel RVP values. Based on this comparison, findings were that it is not necessary to use monthly average values of temperature, humidity, and fuel RVP to accurately estimate annual emissions for most of pollutants except for VOC and CO. This is due to the fact that no significant differences were calculated in emissions using monthly input values compared to emissions calculated using annual average input values. There were about 10% differences in VOC and CO emissions between the two methods.

Monthly variations in VMT affect all emission estimates with the highest VMT occurring in July and the lowest in January. Humidity has the most significant effect on monthly variations of NO_X emission factors. Temperature changes have a smaller effect on NO_X emission factors. VOC and CO emissions are not sensitive to changes in humidity values, but monthly variations in temperatures and fuel RVP values significantly affect VOC and CO emissions.

Different types of vehicles have different emission rates. Annual emissions are affected by the VMT fractions of each vehicle type. Passenger cars and light duty trucks, less than 6000 lbs of gross vehicle weight rating, accounted for over 80% of on-road mobile source emissions of VOC, CO, and NH₃ throughout the state of Tennessee. Fifty four percent of NO_X emissions from on-road mobile sources in Tennessee were from heavy-duty diesel trucks, HDV8A & 8B. The contribution of heavier trucks (HDV8A &8B) to NO_X emissions varies widely (e.g. 9.7% for Hancock County and 79.7% for Haywood County). This is due to differences in truck VMT in counties with and without interstates.

Future year projections in 2009, 2020, and 2030 without VMT growth were conducted for 6 counties in the Knoxville area. NO_X emissions were projected to decrease by 84 to 93.5% for the 6 counties between 2002 and 2030. VOC emissions were projected to decrease by 78%. The projected reductions in PM2.5 emissions were 64.8-83.5%, 91-94% in SO₂ emissions, and 66-68% in CO emissions. Similar reductions would be projected for all Tennessee counties. However, ammonia emissions were projected to increase by 3%. The new regulations affect more reductions on NO_X emissions. If catalytic converter reduces more NO_X, it produces more NH₃ emissions as byproduct. The actual change in future emissions from on-road mobile sources will depend on VMT growth rates.

Recommended Citation

Yun, Jeongran, "On-road Mobile Source Emissions in Tennessee for 2002 – an Inventory and Analysis. " Master's Thesis, University of Tennessee, 2004.
https://trace.tennessee.edu/utk_gradthes/2207