Trends in concentrations of atmospheric gaseous and particulate species in rural eastern Tennessee as related to primary emission reductions

摘要

Air quality measurements at Look Rock, Tennessee – on the western edge ofthe Great Smoky Mountains National Park – were begun in 1980 and expandedduring 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) emissionreductions of SO and NO on air quality at the station. Analysisof temporal trends (1999–2013) has been conducted at the site incollaboration 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 primarypollutant levels have consistently tracked emission reductions from EGUsand other primary sources in the region, but reductions in secondarypollutants such as particulate sulfate and, specifically, ozone have beensmaller compared to reductions in primary emissions. Organic carbonaceousmaterial (OM) remains a major contributor (30–40 % in the period2009–2013) to fine particulate mass at the site, as confirmed by ACSMmeasurements at the site in 2013. A large portion (65–85 %) of carbonin OM derives from modern carbon sources based on C measurements.Important parameters affecting ozone levels, fine mass, and visibility alsoinclude the specific diurnal meteorology at this ridge-top site, itslocation in a predominantly mixed-deciduous forest, and the presence ofprimary sources of precursors at distances of 50–500 km from the site in alldirections.