Abstract
Abstract. Air quality measurements at Look Rock, Tennessee – on the western edge of the Great Smoky Mountains National Park – were begun in 1980 and expanded during the 1980s to a National Park Service (NPS) IMPROVE network station. Measurements were expanded again by the Tennessee Valley Authority (TVA, 1999–2007) to examine the effects of electric generating unit (EGU) emission reductions of SO2 and NOx on air quality at the station. Analysis of temporal trends (1999–2013) has been conducted at the site in collaboration with activities related to the 2013 Southeast Atmosphere Study (SAS) at Look Rock and other southeastern US locations. Key findings from these trend studies include the observation that primary pollutant levels have consistently tracked emission reductions from EGUs and other primary sources in the region, but reductions in secondary pollutants such as particulate sulfate and, specifically, ozone have been smaller compared to reductions in primary emissions. Organic carbonaceous material (OM) remains a major contributor (30–40 % in the period 2009–2013) to fine particulate mass at the site, as confirmed by ACSM measurements at the site in 2013. A large portion (65–85 %) of carbon in OM derives from modern carbon sources based on 14C measurements. Important parameters affecting ozone levels, fine mass, and visibility also include the specific diurnal meteorology at this ridge-top site, its location in a predominantly mixed-deciduous forest, and the presence of primary sources of precursors at distances of 50–500 km from the site in all directions.
Highlights
Observations in and near the Great Smoky Mountains National Park (GSMNP) have been included in many air quality trend analyses for national parks (e.g., Cai et al, 2011; Cooper et al, 2014; U.S National Park Service, 2013)
An era of low natural gas prices has made switching from coal to natural gas very attractive to power producers facing the latest regulatory pressures (U.S Energy Information Administration, 2014), and these actions have triggered further downward movement in emissions of both sulfur dioxide and nitrogen oxide that play a large role in determining air quality over the GSMNP
3.1 Annual trends in gaseous concentrations compared to emissions of primary species
Summary
Observations in and near the Great Smoky Mountains National Park (GSMNP) have been included in many air quality trend analyses for national parks (e.g., Cai et al, 2011; Cooper et al, 2014; U.S National Park Service, 2013). The deployment of a state-of-the-art monitoring system for aerosol chemical speciation at the GSMNP Look Rock monitoring site in 2013 (Budisulistiorini et al, 2015) offers a new opportunity to revisit air quality in the GSMNP with a specific focus on aerosol composition. This paper examines recent air quality trends at Look Rock to enable researchers to place the 2013 data in proper perspective
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