The significance of NOx emissions from coal-fired power plants in the Middle Tennessee area on tropospheric ozone

This thesis examined the significance of NO_x emissions from power plants on tropospheric ozone in the Middle Tennessee area using the Urban Airshed Model. The modeling domain used covers a 46,000 km² rectangle with Nashville, Tennessee located approximately in the center. Located within this area are three coal-fired power plants (Cumberland Steam Plant, Gallatin Steam Plant, and New Johnsonville Steam Plant) which represent the greatest point sources of NO_x emissions within the modeling domain. The emissions are based on a 1990 State Implementation Plan (SIP) inventory that has been backcast to 1988. The emissions, including area, point, mobile, non-road, and biogenic sources were chemically, temporally, and spatially allocated throughout the domain.

The NO_x emissions from the three power plants were reduced by 25%, 50%, 75%, and 100% for two episode dates in 1988 which exceeded the National Ambient Air Quality Standard (NAAQS) for ozone to determine the significance of power plant NO_x emissions on ozone formation. An additional simulation was conducted in which Gallatin's NO_x emissions were reduced by these percentages for a third day in 1988 which also exceeded the NAAQS. The results from this study showed that the maximum ozone that the NO_x emissions from power plants contributed to tropospheric ozone in the Middle Tennessee Area ranged from 19 to 39 parts per billion (ppb) and was predicted to decrease as the NO_x emissions from the power plants were reduced.