Evaluating Temporal Trends of Ambient Air Quality in Charlotte, North Carolina as a Southeastern Boomtown

Abstract

SUNDERMEYER, CHELLY LEE. Evaluating Temporal Trends of Ambient Air Quality in Charlotte, North Carolina as a Southeastern Boomtown. (Under the direction of Dr. Stephen Graham). Ambient air is the air breathed outdoors and can enter indoor environments unaltered. Poor air quality is responsible for adverse health effects and well-being. To protect and improve ambient air quality across the United States, the federal government establishes legislative requirements to control pollutants that contribute to poor air quality. The Clean Air Act requires the United States Environmental Protection Agency to set National Ambient Air Quality Standards (NAAQS) for six criteria air pollutants that can be harmful to public health and the environment: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter (PM2.5/PM10), and sulfur dioxide. Charlotte is a city in the southwest region of North Carolina and one of the fastest growing cities in the country. Charlotte has seen a 60% growth in population in the last decade. Charlotte is potentially facing air quality challenges from its growing population and economy. As in many large cities, Charlotte’s unhealthy air quality is driven by ozone and particulate matter from mobile and stationary emission sources. The construction of new inroads and the growth of nearby/regional supply and demand chains have pushed the area to serve as a significant east coast trucking and freight transportation hub. In this study, Charlotte was evaluated for patterns and trends in ambient air quality occurring over the past 40 years related to changes in population, emissions sources, and energy consumption. Ambient air concentration data for criteria gases, particulates, and lead were compiled to evaluate historical ambient air quality monitoring in Charlotte. County population estimates, state and county emission sources, and state energy consumption data were collected to evaluate relationships between ambient air concentrations and these variables. Fuel sources were shown to impact air quality in Charlotte. Fossil fuels are the top sources of total energy consumed in North Carolina. All petroleum, coal, ii and natural gas represent these fossil fuels. All petroleum is the major energy source contributor at an average over 748,031 BBtu annually. The top six petroleum energy sources are asphalt/road oil, distillate fuel oil, hydrocarbon gas liquids, kerosene, motor gasoline, and residual fuel oil. Motor gasoline is the top energy source consumed over 414,318 BBtu annually. The top emissions sources for most criteria air pollutants were motor gasoline and diesel. Charlotte carbon monoxide 8-hour and 1-hour daily maximum concentrations are substantially reduced in the past 20 years and remained below the NAAQS. Lead’s rolling three-month average concentrations were highest in 1982 at approximately 0.83 μg/m3, declined sharply, and remained negligible for the rest of the study. Nitrogen dioxide daily maximum 1-hour concentrations have remained below the 100 ppb primary NAAQS. Annual mean concentrations are below 53 ppb but, as of 2021, have a slight uptick. Ozone daily maximum 8-hour concentrations were well above 0.070 ppm from 1980-2012, dipping slightly in 2013 and, as of 2019, show an upward trend. PM2.5 short-term annual mean concentrations were above 12.0 μg/m3 from 1999-2007 and have declined. Daily maximum 24-hour concentrations have remained slightly below the NAAQS; however, as of 2020, appear to be trending upward. PM10 daily maximum 24-hour concentrations have remained below the NAAQS since 1999. Sulfur dioxide daily maximum 1-hour concentrations have remained below the NAAQS after 2006 and shows a downward trend. Charlotte continues to improve air quality by regulating industry through administering county, state, and federal regulatory programs and advising the community through education and special programs. Results presented here were based on population, emissions, and energy consumption datasets obtained from the county and state levels with ambient air quality monitors exclusive to the city. Population, emissions, and energy consumption results are assumed to temporally affect the city of Charlotte.